icon

NEW DESIGN:
The ESP website has a completely new look. All of the old content is still there, plus lots more. For a tour of the new design, CLICK HERE.

To send comments or questions about the new design, click HERE.

Viewport Size Code:
Login | Create New Account
picture

  MENU

About | Classical Genetics | Timelines | What's New | What's Hot

About | Classical Genetics | Timelines | What's New | What's Hot

icon

Bibliography Options Menu

icon
SHOW:
Hide Abstracts & Comments
SORT:
By Author   |   By Title   |   By Date

Bibliography on:

The Electronic Scholarly Publishing Project: Providing world-wide, free access to classic scientific papers and other scholarly materials, since 1993.

More About:  ESP | OUR CONTENT | THIS WEBSITE | WHAT'S NEW | WHAT'S HOT

Options Menu: Classical Genetics Publications

icon
SHOW:
Hide Abstracts & Comments
SORT:
By Author   |   By Title   |   By Date

Publications on: Classical Genetics

ESP Library: Classical Genetics

Publications in Classical Genetics

ESP presents a browsable collection of books and papers from the early days of classical genetics. All of this material is available in full-text format on this website.

Featured Publications

Publications: Classical Genetics

Author

Author

Title

Title

Date

Date

Alberts, Hugo W. — 1926.

A Method For Calculating Linkage Values

Genetics, 11: 235-248.

PDF image facsimile file

Altenburg, Edgar and Muller, Hermann J. — 1920.

The Genetic Basis of Truncate Wing,—an Inconstant and Modifiable Character in Drosophila

Genetics, 5: 248.

PDF image facsimile file

Altenburg, Edgar and Muller, Hermann J. — 1920.

The Genetic Basis of Truncate Wing,—an Inconstant and Modifiable Character in Drosophila

Genetics, 5: 1-59.

PDF image facsimile file

Anonymous. — 1844.

Vestiges of the Natural History of Creation.

London: John Churchill.

This is a full-text PDF image facsimile version of the entire 390-page original first edition.

In 1859, many had already begun to think deeply about the meaning and origin of creation. Fifteen years before the Origin, Vestiges of the Natural History of Creation appeared, published anonymously. In one sense, the book is hopelessly dated, and amateurish to boot. In another, the book is incredibly modern - an effort, in the author's own words, "to connect the natural sciences into a history of creation."

At one point, the author (revealed in the 12th edition to be Robert Chambers) uses the example of Charles Babbage's calculating engine (the first computer) to show how apparently miraculous changes might occur as the result of subtle changes in an underlying governing system.

NOTE: This is an electronic FACSIMILE of the original work. The PDF files contain images of the original pages. The files are large and will download slowly. It is probably best to download the files to disk for later viewing and printing. When printed, these files give output equivalent to good quality Xerox copies of the original.

Aristotle. — 350 BC.

On the Generation of Animals.

This is a full-text PDF version of the entire book.

Any collection of critical works in the history of biology must include works by Aristotle.

Aristotle. — 350 BC.

On the Parts of Animals.

This is a full-text PDF version of the entire book.

Any collection of critical works in the history of biology must include works by Aristotle. Here, in On the Parts of Animals, Aristotle provides one of the world's first efforts to understand life in terms of its component parts.

Aristotle. — 350 BC.

The History of Animals.

This is a full-text PDF version of the entire book.

Any collection of critical works in the history of biology must include works by Aristotle. Here, in The History of Animals, Aristotle provides a discussion of the diversity of life, with considerable attention to reproduction and heredity.

Bateson, William, Saunders, E. R., and Punnett, R. C. — 1904.

Experimental Studies in the Physiology of Heredity.

Reports to the Evolution Committee of the Royal Society, II, 1904, pp. 1-131

PDF image facsimile file: 6,907,359 bytes - 154 pages - no figures

William Bateson was the first English-speaking scientist to appreciate the potential significance of Mendel's work. He and his co-workers began immediately to confirm and extend Mendel's findings. This report to the evolution committee of the Royal Society represents one of the very first systematic investigations into Mendelism as a possible general explanation for the fundamental mechanisms of heredity.

Bateson, William, and Saunders, E. R. — 1902.

The facts of heredity in the light of Mendel's discovery.

Reports to the Evolution Committee of the Royal Society, I, 1902, pp. 125-160

PDF typeset file: 543,744 bytes - 41 pages - no figures

William Bateson was the first English-speaking scientist to appreciate the potential significance of Mendel's work. He began working immediately to confirm and extend Mendel's findings. This report to the evolution committee of the Royal Society represents one of the very first systematic investigations into Mendelism as a possible general explanation for the fundamental mechanisms of heredity.

Bateson, William. — 1894.

Materials for the Study of Variation.

London: Macmillan and Company.

This is a full-text PDF image facsimile version of the entire 598-page original first edition.

William Bateson was the first English-speaking scientist to recognize the significance of Mendel's work. Before the rediscovery of Mendel's work in 1900, Bateson had been active in studying morphology, with a special interest in discontinuous variation as it might apply to the origin of species.

In this book Bateson summarizes his observations on discontinuous variation. His concern for this kind of variation probably contributed greatly to the quickness with which he grasped the significance of Mendel's work.

NOTE: This is an electronic FACSIMILE of the original work. The PDF files contain images of the original pages. The files are large and will download slowly. It is probably best to download the files to disk for later viewing and printing. When printed, these files give output equivalent to good quality Xerox copies of the original.

Bateson, William. — 1899.

Hybridisation and cross-breeding as a method of scientific investigation.

Journal of the Royal Horticultural Society, 24:59-66.

PDF typeset file: 89,523 bytes - 13 pages - no figures

In this talk, given in 1899, before Mendel's work had been rediscovered, Bateson gives his vision of what kind of research will be necessary to shed light on the processes of inheritance and evolution:

What we first require is to know what happens when a variety is crossed with its nearest allies. If the result is to have a scientific value, it is almost absolutely necessary that the offspring of such crossing should then be examined statistically. It must be recorded how many of the offspring resembled each parent and how many shewed characters intermediate between those of the parents. If the parents differ in several characters, the offspring must be examined statistically, and marshalled, as it is called, in respect of each of those characters separately.

One would be hard pressed to provide a better anticipation of the experimental approach of Gregor Mendel. Small wonder that Bateson, upon encountering Mendel's work, quickly became convinced that the correct method for studying inheritance was finally at hand.

Bateson, William. — 1900.

Problems of heredity as a subject for horticultural investigation.

Journal of the Royal Horticultural Society, 25:54-61.

PDF typeset file: 84,218 bytes - 12 pages - no figures

Mendel's work of 1865 was largely neglected, until 1900 when it was simultaneously rediscovered by Hugo de Vries, Carl Correns, and Erik von Tschermak. When Mendel's work came to the attention of William Bateson (who himself had already been advocating controlled crosses as an approach to studying heredity), he was convinced that Mendel's work was of major importance:

That we are in the presence of a new principle of the highest importance is, I think, manifest. To what further conclusions it may lead us cannot yet be foretold.

Bateson devoted the remainder of his scientific career to further elucidations of "Mendelism." This present paper captures the enthusiasm of Bateson's first encounter with the works of Mendel.

Bateson, William. — 1902.

Application for Support of an Experimental Investigation of Mendel's Principles of Heredity in Animals and Plants.

In Bateson, B. 1928. William Bateson, F.R.S.: His Essays & Addresses, together with a Short Account of his Life. Cambridge: Cambridge University Press.

PDF typeset file: 36,348 bytes - 6 pages - no figures

Although not considered to be one of the "official" rediscovers of Mendel's work, William Bateson was the first English-speaking scientist to recognize the importance of Mendel's work and he immediately set out to bring Mendel's work to the attention of the scientific community. Bateson coined the word "genetics" to name the new field and made many important contributions to its development.

This present document is a copy of a letter that Bateson wrote in 1902, seeking financial support from the Trustees of the Carnegie Institution for continued investigations into Mendelian mechanisms of inheritance.

The letter was almost certainly the world's first grant application in the new field of genetics. It was declined.

Bateson, William. — 1902.

Mendel's Principles of Heredity: A Defence.

London: Cambridge University Press.

This is a full-text PDF image facsimile version of the entire 212-page original first edition.

William Bateson was the first English-speaking scientist to recognize the significance of Mendel's work. In an 1899 paper, he had anticipated the sort of experimental design that Mendel used, and in 1900, shortly after Mendel's rediscovery, he published another paper in which he summarized Mendel's work in English, declaring it to be "a new principle of the highest importance."

In the present work, Bateson offers a book-length presentation of Mendel's approach to genetic research, including the first English translation of both Mendel's work on peas and his later work on Hieracium. The book is subtitled A Defence because the Mendelian approach to genetics was initially strongly resisted by the biometrician school, which based their thinking on Galton's ancestral law of heredity.

NOTE: This is an electronic FACSIMILE of the original work. The PDF files contain images of the original pages. The files are large and will download slowly. It is probably best to download the files to disk for later viewing and printing. When printed, these files give output equivalent to good quality Xerox copies of the original.

Bateson, William. — 1908.

The Methods and Scope of Genetics.

London: Cambridge University Press.

This is a newly typeset full-text version of the entire 49-page original first edition.

This short book is a copy of the Inaugural Address, given by Bateson upon the creation of the Professorship of Biology at Cambridge. In his introduction, Bateson notes:

The Professorship of Biology was founded in 1908 for a period of five years partly by the generosity of an anonymous benefactor, and partly by the University of Cambridge. The object of the endowment was the promotion of inquiries into the physiology of Heredity and Variation, a study now spoken of as Genetics.

It is now recognized that the progress of such inquiries will chiefly be accomplished by the application of experimental methods, especially those which Mendel's discovery has suggested. The purpose of this inaugural lecture is to describe the outlook over this field of research in a manner intelligible to students of other parts of knowledge.

Here then is a view of how one of the very first practitioners of genetics conceived of the "Methods and Scope of Genetics".

Beadle, G. W. and Emerson, Sterling — 1935.

Further Studies of Crossing Over in Attached-x Chromosomes of Drosophila Melanogaster

Genetics, 20: 192-206.

PDF image facsimile file

Beadle, G. W. and Ephrussi, Boris — 1936.

The Differentiation of Eye Pigments in Drosophila As Studied by Transplantation

Genetics, 21: 225-247.

PDF image facsimile file

Beadle, G. W. and Ephrussi, Boris — 1937.

Development of Eye Colors in Drosophila: Diffusible Substances and Their Interrelations

Genetics, 22: 76-86.

PDF image facsimile file

Belling, John — 1933.

Crossing Over and Gene Rearrangement in Flowering Plants

Genetics, 18: 388-413.

PDF image facsimile file

Bridges, C. B. and Bridges, P. N. — 1938.

Salivary Analysis of Inversion-3r-payne in the "venation" Stock of Drosophila melanogaster

Genetics, 23: 111-114.

PDF image facsimile file

Bridges, Calvin B. — 1914.

Direct proof through non-disjunction that the sex-linked genes of Drosophila are borne on the X-chromosome.

Science, NS vol. XL:107-109.

PDF typeset file: 24,076 bytes - 5 pages - no figures

Although Bridges' longer 1916 Genetics paper (vol 1, page 1) on the same topic is better known and treats the issue at much greater length, this short communication in Science contains the same argument and is equally persuasive.

By 1910, much evidence had been presented to demonstrate that sexual phenotype (i.e., maleness or femaleness) was determined by chromosomes. And, as early as 1902 Sutton noted that similarities in the behavior of genes and chromosomes suggested that Mendelian factors might be carried on chromosomes.

Here, Bridges shows that mis-assortment of the sex chromosomes is accompanied by atypical inheritance patterns for sex-linked traits and he argues that this proves that genes are carried on chromosomes. He concludes his paper: "there can be no doubt that the complete parallelism between the unique behavior of the chromosomes and the behavior of sex-linked genes and sex in this case means that the sex-linked genes are located in and borne by the X-chromosomes."

Bridges, Calvin B. — 1916.

Non-disjunction as proof of the chromosome theory of heredity (part 1).

Genetics, B, 1:1-52.

PDF image facsimile file: 1.808,605 bytes - 52 pages - many figures

This paper was published as the first article in the first volume the new journal genetics. As the title states, the paper offered PROOF that genes are real, physical things that are carried on chromosomes.

This article was scanned from Alfred Sturtevant's personal copy of Genetics. Access to the journal was provided by Edward B. Lewis and Elliot M. Meyerowitz of the California Institute of Technology.

Bridges, Calvin B. — 1916.

Non-disjunction as proof of the chromosome theory of heredity (part 2).

Genetics, B, 1:107-163.

PDF image facsimile file: 2,600,250 bytes - 59 pages - many figures

This paper was published as the first article in the first volume the new journal genetics. As the title states, the paper offered PROOF that genes are real, physical things that are carried on chromosomes.

This article was scanned from Alfred Sturtevant's personal copy of Genetics. Access to the journal was provided by Edward B. Lewis and Elliot M. Meyerowitz of the California Institute of Technology.

Bridges, Calvin B. — 1917.

Deficiency.

Genetics, 2:445-465.

PDF image facsimile file: 21 pages

Bridges, Calvin B. and Mohr, Otto L. — 1919.

The Inheritance of the Mutant Character "vortex"

Genetics, 4: 283-306.

PDF image facsimile file

Bridges, Calvin B., Skoog, Eleanor Nichols, and Li, Ju-chi. — 1936.

Genetical and cytological studies of a deficiency (notopleural) in the second chromosome of Drosophila melanogaster.

Genetics, 21:788-795.

PDF image facsimile file: 8 pages

Bridges, Calvin B., and Anderson, E. G. — 1925.

Crossing over in the X chromosomes of triploid females of Drosophila melanogaster..

Genetics, 10:418-441.

PDF image facsimile file: 24 pages

Bridges, Calvin B., and Mohr, Otto L. — 1919.

The inheritance of the mutant character "vortex".

Genetics, 4:283-306.

PDF image facsimile file: 24 pages

Bridges, Calvin B., and Olbrycht, T. M. — 1926.

The Multiple Stock "xple" and its use.

Genetics, 11:41-55.

PDF image facsimile file: 16 pages

Bridges, Calvin. — 1921.

Triploid intersexes in Drosophila melanogaster.

Science, 54:252-254.

PDF typeset file: 153,521 bytes - 5 pages - no figures

Work in the laboratory of T. H. Morgan was critical in establishing that genes are real, physical entities and that they are arranged in a linear order on chromosomes. Calvin Bridges was a key player in the Morgan group. In 1914, Bridges first demonstrated that a correlation existed between the incorrect assortment of X chromosomes and the incorrect assortment of some genes. In 1916, he expanded on that work to "prove" that sex-linked genes in Drosophila are carried on the X chromosome.

In this paper, Bridges shows that the correlation between mis-assortment of genes and chromosomes applies to the autosomes as well as to the sex chromosomes. In addition, he shows that sex determination in Drosophila appears to be driven by the ratio of X chromosomes to autosomes, not by the absolute number of X chromosomes.

Brink, R. A. and Cooper, D. C. — 1935.

A Proof That Crossing Over Involves an Exchange of Segments Between Homologous Chromosomes

Genetics, 20: 22-35.

PDF image facsimile file

Brooks, W. K. — 1883.

The Law of Heredity, Second Edition.

Baltimore and New York: John Murphy & Co., Publishers.

This is a full-text PDF image facsimile version of the entire 336-page original first edition.

It is often thought that, besides Mendel, little work on heredity occurred during the 19th Century. This is far from true. Darwin's Origin of Species placed the study of inherited variation at the center of biological thought. As this work by Brooks attests, considerable effort was made to understand heredity, especially as it related to natural selection.

Although the details of Brooks' analysis are now outdated, the book provides general insights into late-nineteenth Century thinking on heredity. Since Brooks was one of T. H. Morgan's instructors when Morgan was a student at Johns Hopkins, the book also provides insights into the specific instruction on heredity that was presented to the man who became the first recipient of a Nobel Prize for work on genetics.

NOTE: This is an electronic FACSIMILE of the original work. The PDF files contain images of the original pages. The files are large and will download slowly. It is probably best to download the files to disk for later viewing and printing. When printed, these files give output equivalent to good quality Xerox copies of the original.

Cannon, W. A. — 1902.

A cytological basis for the Mendelian laws.

Bulletin of the Torrey Botanical Club, 29:657-661.

PDF typeset file: 191,965 bytes - 6 pages

Castle, W. E. — 1938.

The Relation of Albinism to Body Size in Mice

Genetics, 23: 269-274.

PDF image facsimile file

Castle, W. E. and Reed, S. C. — 1936.

Studies of Inheritance in Lop-eared Rabbits

Genetics, 21: 297-309.

PDF image facsimile file

Castle, W. E. — 1911.

Heredity in Relation to Evolution and Animal Breeding.

New York: D. Appleton and Company

This is an image facsimile version of the entire 184-page original edition.

Castle, W. E. — 1913.

Simplification of Mendelian formulae.

The American Naturalist, 47:170-182

PDF typeset file: 69,294 bytes - 13 pages - no figures

Soon after Mendel was rediscovered, the nature of the gene was being worked out. Along the way, many suggested changes to the symbology being used (e.g., B for dominant allele, b for recessive). Here Castle offers some suggestions for changing Mendelian symbols.

Castle, W. E. — 1923.

The relation of Mendelism to mutation and evolution.

The American Naturalist, 57:559-561

PDF typeset file: 30,865 bytes - 5 pages - no figures

Here Castle offers a short note relating the behavior of simple Mendelian characters to the more complex, quantitative traits found in natural populations (and thus of interest to those studying evolution).

Castle, W. E. — 1925.

A Sex Difference in Linkage in Rats and Mice

Genetics, 10: 580-582.

PDF image facsimile file

Castle, W. E., Gates, W. H., Reed, S. C. and Law, L. W. — 1936.

Studies of a Size Cross in Mice, II

Genetics, 21: 310-323.

PDF image facsimile file

Castle, W. E., Gates, W. H., and Reed, S. C. — 1936.

Studies of a Size Cross in Mice

Genetics, 21: 66-78.

PDF image facsimile file

Castle, W. E., and Little, C. C. — 1910.

On a modified Mendelian ratio among yellow mice.

Science, N.S., 32:868-870.

PDF typeset file: 39,133 bytes - 7 pages - no figures

Here, Castle and Little offer evidence consistent with the idea that the gene for yellow fur in mice, studied earlier by Cuénot, is probably lethal when carried homozygously.

Castle, W. E., and Wachter, W. L. — 1924.

Variations of Linkage in Rats and Mice

Genetics, 9: 1-12.

PDF image facsimile file

Castle, W.E. — 1919.

Is the arrangement of the genes in the chromosome linear?

Proceedings of the National Academy of Sciences, 5:25-32.

PDF image facsimile file: 615,957 bytes - 8 pages

Charles W. Metz, Charles W. — 1918.

The Linkage of Eight Sex-linked Characters in Drosophila virilis

Genetics, 3: 107-134.

PDF image facsimile file

Cook, O. F. — 1909.

Pure Strains as Artifacts of Breeding

The American Naturalist 43: 241-242.

Cook, Robert. — 1937.

A chronology of genetics.

Yearbook of Agriculture, pp. 1457-1477.

PDF typeset file: 251,867 bytes - 28 pages - one figure

Robert Cook, as editor of The Journal of Heredity, was especially well positioned to appreciate how the new science of genetics developed after the rediscovery of Mendel in 1900 and the establishment of the chromosome theory of inheritance by T. H. Morgan and his students.

In this essay, Cook traces the history of genetics to four main roots - mathematics, plant breeding, animal breeding, and cytology.

Correns, Carl — 1900.

G. Mendel's law concerning the behavior of progeny of varietal hybrids.

First published in English as: Correns, C., 1950. G. Mendel's law concerning the behavior of progeny of varietal hybrids. Genetics, 35(5, pt 2): 33-41. Originally published as: Correns, C. 1900. G. Mendels Regel über das Verhalten der Nachkommenschaft der Rassenbastarde. Berichte der Deutschen Botanischen Gesellschaft, 18: 158-168.

PDF typeset file: 78,900 bytes - 14 pages - no figures

Correns, along with Hugo de Vries and Erik von Tschermak, is considered to be one of the three co-discovers of Mendel's work in 1900. Correns was the only one of the three to acknowledge Mendel in the title of his paper. Correns' paper begins:

The latest publication of Hugo de Vries: Sur la loi de disjonction des hybrides, which through the courtesy of the author reached me yesterday, prompts me to make the following statement: In my hybridization experiments with varieties of maize and peas, I have come to the same results as de Vries, who experimented with varieties of many different kinds of plants, among them two varieties of maize. When I discovered the regularity of the phenomena, and the explanation thereof - to which I shall return presently - the same thing happened to me which now seems to be happening to de Vries: I thought that I had found something new. But then I convinced myself that the Abbot Gregor Mendel in Brünn, had, during the sixties, not only obtained the same result through extensive experiments with peas, which lasted for many years, as did de Vries and I, but had also given exactly the same explanation, as far as that was possible in 1866.

Cox, Charles F. — 1909.

Charles Darwin and the Mutation Theory

The American Naturalist 43: 65-91.

Creighton, Harriet B., and McClintock, Barbara. — 1931.

A correlation of cytological and genetical crossing-over in Zea mays.

PNAS, 17:492-497.

PDF image facsimile file: 6 pages - several figures

When Alfred Sturtevant created the first genetic map, he hypothesized that genetic recombination resulted from the actual exchange of chromatid fragments. However, at the time there was no hard evidence that proved recombination is accomplished via such a mechanism. The same genetic results could be explained if only alleles are exchanged during recombination, leaving the bulk of the chromatid arm unaffected. Since the two hypotheses make equivalent predictions regarding the distribution of alleles, they cannot be distinguished using purely genetic methods.

Attempting to demonstrate that genetic recombination is accomplished via the physical exchange of chromatid arms poses a problem similar to that encountered by Thomas H. Morgan when he first hypothesized that genes might be carried on the X chromosome. Although Morgan's genetic hypothesis of X-linkage provided an explanation for the inheritance of the white-eye allele in Drosophila, the notion that genes are actually carried on the X chromosome was not proven until Calvin Bridges provided cytological evidence to confirm the genetic observations. Bridges established a one-to-one correspondence between the abnormal distribution of eye-color alleles and the abnormal distribution of X chromosomes. That is, he established a relationship between genetic markers (the eye color alleles and their associated inheritance patterns) and cytological markers (the presence of abnormal sets of sex chromosomes).

In this paper, Creighton and McClintock present work in which they use a combination of cytological and genetic markers to show that cytological crossing-over occurs and that it is accompanied by genetical crossing-over. In just a few pages the authors accomplish their goal of establishing the reality of cytological recombination and of showing that it is associated with genetic recombination. This paper is truly a classic.

If this paper is read in isolation, the authors' discussion of their results can, at times, be difficult to follow. When this paper was originally published, however, it was accompanied by another paper (by McClintock) that immediately preceded it in the journal and that was intended to serve as an introduction to this paper. In the preceding paper, McClintock provided the basic genetic and cytological information necessary to understand the experimental logic of this paper. The background paper is The order of the genes C, Sh, and Wx in Zea mays with reference to a cytologically known point in the chromosome. The two papers should be read together, with the first, descriptive paper serving as a critical and necessary introduction to the second, experimental work.

For additional commentary on Creighton and McClintock's important work, see Edward Coe and Lee B. Kass (2005) Proof of physical exchange of genes on the chromosomes. Proceedings of the National Academy of Sciences, USA. 102:6641-6646.

Creighton, Harriet B., and McClintock, Barbara. — 1931.

A correlation of cytological and genetical crossing-over in Zea mays.

PNAS, 17:492-497.

PDF typeset file: 140,176 bytes - 17 pages - several figures

When Alfred Sturtevant created the first genetic map, he hypothesized that genetic recombination resulted from the actual exchange of chromatid fragments. However, at the time there was no hard evidence that proved recombination is accomplished via such a mechanism. The same genetic results could be explained if only alleles are exchanged during recombination, leaving the bulk of the chromatid arm unaffected. Since the two hypotheses make equivalent predictions regarding the distribution of alleles, they cannot be distinguished using purely genetic methods.

Attempting to demonstrate that genetic recombination is accomplished via the physical exchange of chromatid arms poses a problem similar to that encountered by Thomas H. Morgan when he first hypothesized that genes might be carried on the X chromosome. Although Morgan's genetic hypothesis of X-linkage provided an explanation for the inheritance of the white-eye allele in Drosophila, the notion that genes are actually carried on the X chromosome was not proven until Calvin Bridges provided cytological evidence to confirm the genetic observations. Bridges established a one-to-one correspondence between the abnormal distribution of eye-color alleles and the abnormal distribution of X chromosomes. That is, he established a relationship between genetic markers (the eye color alleles and their associated inheritance patterns) and cytological markers (the presence of abnormal sets of sex chromosomes).

In this paper, Creighton and McClintock present work in which they use a combination of cytological and genetic markers to show that cytological crossing-over occurs and that it is accompanied by genetical crossing-over. In just a few pages the authors accomplish their goal of establishing the reality of cytological recombination and of showing that it is associated with genetic recombination. This paper is truly a classic.

If this paper is read in isolation, the authors' discussion of their results can, at times, be difficult to follow. When this paper was originally published, however, it was accompanied by another paper (by McClintock) that immediately preceded it in the journal and that was intended to serve as an introduction to this paper. In the preceding paper, McClintock provided the basic genetic and cytological information necessary to understand the experimental logic of this paper. The background paper is The order of the genes C, Sh, and Wx in Zea mays with reference to a cytologically known point in the chromosome. The two papers should be read together, with the first, descriptive paper serving as a critical and necessary introduction to the second, experimental work.

For additional commentary on Creighton and McClintock's important work, see Edward Coe and Lee B. Kass (2005) Proof of physical exchange of genes on the chromosomes. Proceedings of the National Academy of Sciences, USA. 102:6641-6646.

Creighton, Harriet B., and McClintock, Barbara. — 1935.

A correlation of cytological and genetical crossing-over in Zea mays. A Corroboration.

PNAS, 21:148-150.

PDF image facsimile file: 3 pages - no figures

Although Creighton and McClintock's 1931 paper — A correlation of cytological and genetical crossing-over in Zea mays. — had provided data in support of the notion that cytological crossing-over occurs and that it is accompanied by genetical crossing-over, some had criticized the relatively few data points in the paper. In this 1935 paper, the authors acknowledge the criticism, then explain why they will, in this paper, be sharing some additional corroborative data with little additional commentary:

There has recently been some skepticism expressed (Brink and Cooper, 1935) as to the value of the studies on the correlation of cytological and genetical crossing-over in maize published by Creighton and McClintock (1931) because of the fewness of the data. Since the paper by Stern (1931) dealing with Drosophila and having much more extensive data appeared at practically the same time and yielded the same conclusions, the authors felt it unnecessary to add to the ever-increasing amount of published work merely to record more evidence of the same nature without supplying anything essentially new or advancing. Therefore, confirmatory data which have accumulated since the time the joint paper mentioned above was published have not been considered for a separate publication. However, we now feel forced to add more data merely to counteract any suspicion that the evidence previously presented constituted insufficient proof. This will be done in as brief a form as possible, since a discussion of the method has been given in the paper mentioned above.

For additional commentary on Creighton and McClintock's important work, see Edward Coe and Lee B. Kass (2005) Proof of physical exchange of genes on the chromosomes. Proceedings of the National Academy of Sciences, USA. 102:6641-6646.

Crew, F. A. E. — 1969.

Recollections of the early days of the genetical society.

In John Jinks, The Genetical Society - The First Fifty Years, Edinburgh: Oliver and Boyd, pp.9-15.

PDF image facsimile file: 7 pages

Darbishire, A. D. — 1905.

On the supposed antagonism of Mendelian to biometric theories of heredity.

Manchester Memoirs, 49:1-19.

PDF typeset file: 16 pages

Darwin, C. — 1845.

The Voyage of the Beagle, Second Edition.

London: John Murray.

This is a full-text, newly typeset, PDF version of the entire book.

For five years, from 1831-1836, Charles Darwin served as the official naturalist aboard the HMS Beagle as it visited exotic locations around the world. During this voyage, Darwin first came to wonder about the mechanisms driving the origin of species. This book chronicles the voyage and documents his early thinking.

Darwin, C. — 1859.

On the Origin of Species.

London: John Murray, Albemarle Street.

This is a full-text PDF image facsimile version of the entire 502-page original first edition.

This is the book that changed the world and defined modern biology. By making mechanisms of heritable variation central to the biggest issue in all of biology, Darwin initiated the genetics revolution.

Darwin, C. — 1883.

The Variation of Animals and Plants Under Domestication, Second Edition, Revised (two volumes).

New York: D. Appleton & Co.

This is a full-text PDF image facsimile version of the entire 473-page volume I and the entire 495-page volume II of the original work.

Although Darwin's theories regarding the origin of species through natural selection required that some mechanism of heredity exist, no such mechanism was known when the Origin was written. After the Origin appeared, Darwin turned his attention to the mechanism(s) of heredity, resulting in his subsequent two-volume The Variation of Animals and Plants Under Domestication.

In volume I, Darwin summarized what was known about inheritance in a variety of domesticated species and concluded with a chapter, Inheritance, that begins his general summary of the mechanisms of inheritance. He continued this summary in volume II, which also offers Darwin's own theory of inheritance in Chapter XXVII, Provisional Hypothesis of Pangenesis.

The notion of pangenesis dominated late nineteenth-century thinking about inheritance. Although ultimately seen to be simply wrong, it was very influential and a familiarity with its tenets is essential for anyone wishing to understand the intellectual climate at the time Mendel was rediscovered in 1900.

NOTE: This is an electronic FACSIMILE of the original work. The PDF files contain images of the original pages. The files are large and will download slowly. It is probably best to download the files to disk for later viewing and printing. When printed, these files give output equivalent to good quality Xerox copies of the original.

Davenport, C. B. — 1930.

Sex linkage in man

Genetics, 15: 401-444.

PDF image facsimile file

Davenport, Charles B. — 1917.

Inheritance of Stature

Genetics, 2: 313-389.

PDF image facsimile file

Davenport, Gertrude C, and Davenport, Charles B. — 1909.

Heredity of Hair Color in Man

The American Naturalist 43: 193-211.

Davis, Bradley M. — 1909.

The Permanence of Chromosomes in Plant Cells

The American Naturalist

Demerec, M. — 1923.

Inheritance of White Seedlings in Maize

Genetics, 8: 561-593.

PDF image facsimile file

Demerec, M. — 1937.

Frequency of Spontaneous Mutations in Certain Stocks of Drosophila melanogaster

Genetics, 22: 469-478.

PDF image facsimile file

Demerec, Milislav — 1933.

What is a Gene?

Journal of Heredity, 24:368-378.

PDF typeset file: 679,936 bytes - 22 pages - several figures

Once the foundations of transmission genetics had been worked out, researchers began to consider what the chemical nature of the gene might be. Here Milislav Demerec offers one of the first such efforts. He concludes that the gene is a minute organic particle, capable of reproduction, located in a chromosome and responsible for the transmission of a hereditary characteristic. Moreover, he states that the available evidence suggests that genes are uni-molecular, and he notes:

If a gene is a complex organic molecule it would be expected to be similar in composition to other complex molecules, viz. molecular groups constituting this molecule (whatever these groups may be) would he arranged in chains and side chains. He then offers a drawing of the structure of DNA (!) as an example of a complex organic molecule, but is quick to add that The diagram is not intended to give any implication as to the number, the type, or the arrangement of the molecules in a gene group. Its purpose is to illustrate the molecular structure of a complex organic molecule.

Another 20 years would have to pass before the true chemical nature of the gene would be established.

Dobzhansky, T. — 1930.

Translocations involving the third and the fourth chromosomes of Drosophila melanogaster

Genetics, 15: 347-399.

PDF image facsimile file

Dobzhansky, Th. — 1937.

Further Data on the Variation of the Y Chromosome in Drosophila Pseudoobscura

Genetics, 22: 340-346.

PDF image facsimile file

Dobzhansky, Th. and Beadle, G. W. — 1936.

Studies on Hybrid Sterility IV. Transplanted Testes in Drosophila Pseudoobscura

Genetics, 21: 832-840.

PDF image facsimile file

Dobzhansky, Th. and Sturtevant, A. H. — 1938.

Inversions in the Chromosomes of Drosophila Pseudoobscura

Genetics, 23: 28-64.

PDF image facsimile file

Dobzhansky, Th. — 1935.

Drosophila Miranda, a New Species

Genetics, 20: 377-391.

PDF image facsimile file

Dobzhansky, Th. — 1935.

The Y Chromosome of Drosophila Pseudoobscura

Genetics, 20: 366-376.

PDF image facsimile file

Dobzhansky, Th. — 1936.

Studies on Hybrid Sterility. II. Localization of Sterility Factors in Drosophila Pseudoobscura Hybrids

Genetics, 21: 113-135.

PDF image facsimile file

Dobzhansky, t. — 1931.

Translocations Involving the Second and the fourth chromosomes of Drosophila melanogaster

Genetics, 16: 629-658.

PDF image facsimile file

Doncaster, L. — 1911.

Heredity in the Light of Recent Research.

Cambridge: University Press

This is an image facsimile version of the entire 144-page original first edition.

Drinkwater, H. — 1910.

A Lecture on Mendelism.

London: J. M. Dent & Sons.

This is an image facsimile version of the entire 48-page original first edition.

This short book was based on a lecture given by Drinkwater as one of a series known as "Science Lectures for the People." The book provides insights into the general perception (as opposed to scholarly view) of genetics very early after the field had begun.

The book also contains some nice portraits of Mendel, Bateson, and Punnett.

Dunn, L. C. — 1920.

Independent Genes in Mice

Genetics, 5: 344-361.

PDF image facsimile file

Dunn, L. C. — 1920.

Linkage in Mice and Rats

Genetics, 5: 325-343.

PDF image facsimile file

East - Morgan - Harris - Shull — 1923.

The Centenary of Gregor Mendel and of Francis Galton.

The Scientific Monthly, 16: 225-270.

PDF typeset file: 247,951 bytes - 54 pages - no figures

In December of 1922, the American Society of Naturalists held a special session to honor the centenaries of the birth of Gregor Mendel and of Francis Galton. This is the collection of the four papers presented at that session and later published in the The Scientific Monthly.

East, E. M. — 1916.

Studies on Size Inheritance in Nicotiana

Genetics, 1:164-176.

PDF image facsimile file

East, E. M. — 1923.

Mendel and his contemporaries.

The Scientific Monthly, 16: 225-237.

PDF typeset file: 247,951 bytes - 54 pages - no figures

In December of 1922, the American Society of Naturalists held a special session to honor the centenaries of the birth of Gregor Mendel and of Francis Galton. This is one of the four papers presented at that session and later published in the The Scientific Monthly.

East, E. M. — 1929.

The concept of the gene.

Proceedings of the International Congress of Plant Sciences, Ithaca, New York, August 16-23, 1926, vol. 1. Menasha, WI: George Banta Publishing Co. pp 889-895.

PDF typeset file: 76,104 bytes - 11 pages - no figures

As classical genetics acquired more and more explanatory power, the question what is a gene? became more important. Were genes real physical entities, or merely theoretical concepts that allowed for the mathematical modelling of inheritance. This paper represents one effort to consider The concept of the gene. The paper's opening paragraph sets the tone:

Nearly fifteen years ago I attempted to defend the thesis that the Mendelian method of recording the facts of inheritance was simply a notation useful as a description of physiological facts. The argument was an elaboration of the proposition that the germ-cell unit of heredity, the gene, was an abstract, formless, characterless concept used for convenience in describing the results of breeding experiments. It was the ghost of an entity which might later be clothed with flesh, but its usefulness at the time was due to its adaptability to mathematical treatment. By postulating that the results derived from controlled matings were due to the activities of definite germ-cell units which could be manipulated arithmetically, investigators were able to formulate new experimental tests, and thus to open the way to further discovery; but these units could be given no intelligible interpretation in terms of geometry, chemistry, or physiology.

In the last paragraph, East asserts:

We arrive, therefore, at the same port from which we departed when our discussion began. The genes are units useful in concise descriptions of the phenomena of heredity. Their place of residence is the chromosomes. Their behavior brings about the observed facts of genetics. For the rest, what we know about them is merely an interpretation of crossover frequency. In terms of geometry, chemistry, physics or mechanics, we can give them no description whatever.

East, E. M. — 1936.

Heterosis

Genetics, 21: 375-397.

PDF image facsimile file

East, Edward M. — 1909.

The Distinction between Development and Heredity in Inbreeding.

The American Naturalist 43: 173-181.

Ephrussi, Boris and Beadle, G. W. — 1937.

Development of Eye Colors in Drosophila: Production and Release of cn+ Substance by the Eyes of Different Eye Color Mutants

Genetics, 22: 479-483.

PDF image facsimile file

Ephrussi, Boris and Beadle, G. W. — 1937.

Development of Eye Colors in Drosophila: Transplantation Experiments on the Interaction of Vermilion with Other Eye Colors

Genetics, 22: 65-75.

PDF image facsimile file

Fisher, R. A. , Immer, F. R., and Tedin, Olof — 1932.

The Genetical Interpretation of Statistics of the Third Degree in the Study of Quantitative Inheritance

Genetics, 17: 107-124.

PDF image facsimile file

Fisher, R. A. — 1919.

The Genesis of Twins

Genetics, 4: 489-499.

PDF image facsimile file

Gager, Charles Stuart — 1908.

Some Physiological Effects of Radium Rays

The American Naturalist 42: 761-778.

Galton, Francis — 1889.

Natural Inheritance.

London: Macmillan

This is an image facsimile version of the entire 260-page original first edition.

Galton, Francis — 1889.

Natural Inheritance.

London: Macmillan

This is an image facsimile version of the entire 260-page original first edition.

Galton, Francis. — 1898.

A Diagram of Heredity.

Nature, 57:293.

PDF typeset file: 27,776 bytes - 5 pages - one figure

Some standard textbook descriptions of early genetics give the impression that, besides Mendel, no one attempted any genetic analysis in the entire nineteenth century. This is far from the truth, with Francis Galton offering a fine refutation. Starting just a few years after Mendel (and also working with peas), Galton carried out a series of well-received studies that resulted in his "Ancestral Law of Heredity," summarized diagrammatically in this brief communication. Galton's "Law" was so firmly established in some circles, that many adherents did not accept Mendelism until 1918, when R. A. Fisher showed that Galton's Law was in fact a natural consequence of Mendelian inheritance for polygenic traits.

Garrod, Archibald E. — 1902.

The incidence of alkaptonuria: A study in chemical individuality.

Lancet, ii:1616-1620.

PDF typeset file: 145,052 bytes - 18 pages - no figures

This paper is a true classic. Like Mendel's own work, this report offers insights so far ahead of its time that it, and Garrod's follow-on work, were largely neglected, until later efforts to elucidate the physiological functioning of genes led to the Nobel-prize-winning one-gene, one-enzyme hypothesis.

Less than two years after the rediscovery of Mendelism and just a few years after the word biochemistry was first coined, Garrod reports on alkaptonuria in humans and comes to the conclusion that it is inherited as a Mendelian recessive and that the occurrence of mutations (sports in the word of the time) in metabolic function should be no more surprising than inherited variations in morphology.

Garrod, Archibald. — 1923.

Inborn Errors of Metabolism, Second Edition.

London: Henry Frowde and Hodder & Stoughton

This is a full-text PDF image facsimile version of the entire 216-page original book.

Less than two years after the rediscovery of Mendelism and just a few years after the word biochemistry was first coined, Garrod reported on alkaptonuria in humans and came to the conclusion that it was inherited as a Mendelian recessive and that the occurrence of mutations (sports in the word of the time) in metabolic function should be no more surprising than inherited variations in morphology.

In 1908, he summarized his thinking about "inborn errors of metabolism" (his term for what we would now think of as mutations in genes affecting metabolic function) in a book. An image facsimile of the second edition (1923) of that book is presented here.

Like Mendel's work, Garrod's insights were so far ahead of their time that his entire work on metabolic mutations was largely neglected, until later efforts to elucidate the physiological functioning of genes led to the Nobel-prize-winning one-gene, one-enzyme hypothesis.

Goldschmidt, Richard — 1917.

Crossing Over ohne Chiasmatypie?

Genetics, 2:82-95.

PDF image facsimile file: 764,480 bytes - 14 pages - 2 figures

Haldane, J. B. S. — 1934.

A Mathematical Theory of Natural and Artificial Selection Part X. Some Theorems on Artificial Selection

Genetics, 19: 412-429.

PDF image facsimile file

Haldane, J. B. S. and Waddington, C. H. — 1931.

Inbreeding and Linkage

Genetics, 16: 357-374.

PDF image facsimile file

Hardy, G. H. — 1908.

Mendelian Proportions in a Mixed Population.

Science, NS. XXVIII:49-50.

PDF typeset file: 19,473 bytes - 1 page - no figures

Every geneticist has heard of the Hardy-Weinberg Law and of Hardy-Weinberg Equilibrium, and nearly all basic biology texts teach that G. H. Hardy played a seminal role in founding population genetics. But, what most biologists don't realize is that Hardy's total contribution to biology consisted of a single letter to the editor in Science. The letter began,

I am reluctant to intrude in a discussion concerning matters of which I have no expert knowledge, and I should have expected the very simple point which I wish to make to have been familiar to biologists. However, some remarks of Mr. Udny Yule, to which Mr. R. C. Punnett has called my attention, suggest that it may still be worth making.

With that, Hardy offered his "simple point" and then washed his hands of biology. His autobiography, A Mathematician's Apology, makes no mention of population genetics.

Harnly, Morris Henry and Ephrussi, Boris — 1937.

Development of Eye Colors in Drosophila: Time of Action of Body Fluid on Cinnabar

Genetics, 22: 393-401.

PDF image facsimile file

Harris, J. Arthur — 1923.

Galton and Mendel: Their contribution to genetics and their influence on biology.

The Scientific Monthly, 16: 247-263.

PDF typeset file: 247,951 bytes - 54 pages - no figures

In December of 1922, the American Society of Naturalists held a special session to honor the centenaries of the birth of Gregor Mendel and of Francis Galton. This is one of the four papers presented at that session and later published in the The Scientific Monthly.

Hurst, C. C. — 1904.

Experiments with Poultry.

Reports to the Evolution Committee of the Royal Society, II, 1904, pp. 131-154

PDF image facsimile file: 6,907,359 bytes - 154 pages - no figures

William Bateson was the first English-speaking scientist to appreciate the potential significance of Mendel's work. He and his co-workers began immediately to confirm and extend Mendel's findings. C. C. Hurst was one of Wm Bateson's early co-workers. This report to the evolution committee of the Royal Society represents one of the very first systematic investigations into Mendelism as a possible general explanation for the fundamental mechanisms of heredity.

Huxley, T. H. — 1869.

Nature: Aphorisms by Goethe.

Nature, 1:9-11.

PDF image facsimile file: 343,040 bytes - 3 pages

A special article, written by Huxley on request for the first issue of Nature, a new publication. The article is mainly a lengthy quote from Goethe, consisting of an extended rhapsody on "Nature."

Ibsen, Heman L. — 1916.

Tricolor Inheritance. II. the Basset Hound

Genetics, 1: 367-376.

PDF image facsimile file

Ibsen, Heman L. — 1916.

Tricolor Inheritance. III. Tortoiseshell Cats

Genetics, 1: 377-386.

PDF image facsimile file

Ibsen, Heman L. — 1916.

Tricolor Inheritance. I. the Tricolor Series in Guinea-pigs

Genetics, 1: 287-309.

PDF image facsimile file

Ibsen, Heman L. — 1919.

Tricolor Inheritance. Iv. the Triple Allelo-morphic Series in Guinea-pigs

Genetics, 4: 597-606.

PDF image facsimile file

Jones, Donald F. (ed) — 1932.

Proceedings of the Sixth International Congress of Genetics, Vol. I.

Austin, Texas: Genetics Society of America

This is an image facsimile version of the entire 396-page original edition.

The Proceedings of the Sixth International Congress of Genetics, held in 1932, offers a glimpse into classical genetics at the height of its power and influence. Thomas Morgan, who had just received the first Nobel Prize ever awarded in genetics, served as president of the congress.

The participants list reads like a who's who of classical genetics: The three rediscovers of Mendel - Correns, de Vries, and von Tschermak - all attended the meeting. Morgan, Sturtevant, and Muller gave talks. Population genetics and the relationship of genetics to evolution was discussed by R. A. Fisher, J. B. S. Haldane, and Sewall Wright.

According to the Treasurer's Report, the total cost of the meeting was $17,583.58.

Little, C. C. — 1914.

A possible Mendelian explanation for a type of inheritance apparently non-Mendelian in nature

Science, 40:904-906.

PDF image facsimile file: 530,978 bytes - 3 pages

Little, C. C. — 1917.

The Relation of Yellow Coat Color and Black-eyed White Spotting of Mice in Inheritance

Genetics, 2: 433-444.

PDF image facsimile file

Luria, S. E., and Delbrück, M. — 1943.

Mutations of bacteria from virus sensitivity to virus resistance.

Genetics, 28:491-511

PDF typeset file: 201,354 bytes - 37 pages - several figures

This classic paper is the "fluctuation test" in which Luria and Delbrü first demonstrated the occurrence of microbial genetics. In fact, the fluctuation test must be regarded as the founding of bacterial genetics since it gave the first real proof that bacteria both possessed genes and experienced mutation. Luria and Delbrück shared the 1969 Nobel Prize with Alfred Hershey.

Luria and Delbrück were also able to use their data to calculate the actual mutation rate per bacterial cell division. Averaged across all of their experiments, this came to approximately 2.45 x 10-8. Thus, they not only proved that true genetic mutations occurred in bacteria, but also that such mutations were just as rare in bacteria as they were in higher organisms. Their work demonstrated that heritable variation in bacteria could be attributed to mechanisms similar to those in higher organisms. The previously puzzling ability of bacteria to respond rapidly and adaptively to changes in the environment could now be recognized as nothing more than the normal consequence of random gene mutation, followed by selection, in huge, rapidly reproducing populations.

Following this discovery, many researchers hurried to determine the range of true genetic mutation occurring in bacteria. Soon, such variation was detected in virtually every trait that could be studied, such as color, colony morphology, virulence (ability to infect a host), resistance to antimicrobial agents, nutritional requirements, and fermentation abilities (i.e., the ability to use different compounds as carbon sources).

Macarthur, John W. — 1933.

Sex-linked Genes in the Fowl

Genetics, 18: 210-220.

PDF image facsimile file

Malthus, T. — 1798.

An Essay on the Principle of Population.

PDF typeset file: 948,754 bytes - 134 pages - no figures

In 1798, Thomas Malthus anonymously published this Essay, outlining why the forces of population growth tend to create a "struggle for existence" (see page 14). This book had a significant influence on Darwin as he looked for mechanisms that might explain evolutionary change. The influence shows, with Chapter Three of Darwin's Origin of Species entitled "Struggle for Existence". Now, 200 years after its first publication, Malthus' work is still an interesting read.

McClintock, Barbara and Hill, Henry E. — 1931.

The cytological identification of the chromosome associated with the r-g linkage group in Zea mays

Genetics, 16: 175-190.

PDF image facsimile file

McClintock, Barbara — 1929.

A cytological and genetical study of triploid maize

Genetics, 14: 180-222.

PDF image facsimile file

McClintock, Barbara. — 1931.

The order of the genes C, Sh, and Wx in Zea mays with reference to a cytologically known point in the chromosome.

PNAS, 17:485-491.

PDF image facsimile file: 7 pages - several figures

In this paper, McClintock provides the basic genetic and cytological information necessary to understand the logic of her classic work with Harriet Creighton: A correlation of cytological and genetical crossing-over in Zea mays that appeared immediately following this paper in PNAS.

For additional commentary on Creighton and McClintock's important work, see Edward Coe and Lee B. Kass (2005) Proof of physical exchange of genes on the chromosomes. Proceedings of the National Academy of Sciences, USA. 102:6641-6646.

McClung, C. E. — 1901.

Notes on the accessory chromosome.

Anatomischer Anzeiger, 20:220-226.

PDF typeset file: 58,569 bytes - 12 pages - no figures

In this brief paper, McClung introduces the evidence that male and female insects exhibit different chromosomal structures in their nuclei and that spermatozoa fall into two types - those that carry the "accessory chromosome" and those that do not.

Based on this analysis, McClung suggests that the presence or absence of the "accessory chromosome" in spermatozoa may determine the sex of the progeny. McClung published this short note in 1901 to alert the scientific community of his findings and to alert them to a more detailed argument that he had already submitted for publication elsewhere and that he knew would appear a year later, in McClung, C. E. 1902. The accessory chromosome - Sex determinant? Biological Bulletin, 3:43-84.

McClung, C. E. — 1902.

The accessory chromosome - Sex determinant?

Biological Bulletin, 3:43-84.

PDF typeset file: 188,601 bytes - 40 pages - no figures

In this paper, McClung analyzes the evidence that male and female insects exhibit different chromosomal structures in their nuclei and that spermatozoa fall into two types - those that carry the "accessory chromosome" and those that do not.

Based on this analysis, McClung offers the bold hypothesis that the presence or absence of the "accessory chromosome" in spermatozoa may determine the sex of the progeny:

A most significant fact ... is that the [accessory chromosome] is apportioned to but one half of the spermatozoa. Assuming it to be true that the chromatin is the important part of the cell in the matter of heredity, then it follows that we have two kinds of spermatozoa that differ from each other in a vital matter. We expect, therefore, to find in the offspring two sorts of individuals in approximately equal numbers. ... [Since] nothing but sexual characters ... divides the members of a species into two well-defined groups, ... we are logically forced to the conclusion that the [accessory] chromosome has some bearing upon this arrangement.

That is, McClung hypothesizes that a difference in chromosome number is the cause, not an effect, of sex determination. This paper represents the first effort to associate the determination of a particular trait with a particular chromosome.

Mendel - de Vries - Correns - Tschermak — 1950.

The Birth of Genetics

Special supplement to the journal Genetics 35(5, pt 2): 1-48.

PDF typeset file: 344,064 bytes - 66 pages - no figures

To celebrate the fiftieth anniversary of the rediscovery of Mendel's work, the Genetics Society of America published this special supplement, containing translations of the original papers by the rediscovers of Mendel - Carl Correns, Erik von Tschermak, and Hugo de Vries. It also contains letters written by Mendel and sent to Carl Nägeli, a leading botanist.

This was the first time these key works were made available in English translation.

Mendel, Gregor — 1866-1873.

Gregor Mendel's letters to Carl Nägeli, 1866-1873.

First published in English as: Mendel, G. 1950. Gregor Mendel's Letters to Carl Nägeli. Genetics, 35(5, pt 2): 1-29. Originally published as: Abhandlungen der Mathematisch-Physischen Klasse der Königlich Sächsischen Gesellschaft der Wissenschaften 29: 189-265, 1905. Reprinted in "Carl Correns, Gesammelte Abhandlungen zur Vererbungswissenschaft aus periodischen Schriften" 1899-1924. (Fritz V. Wettstein ed.) Berlin, Julius Springer, 1924. pp. 1237-1281.

PDF typeset file: 206,438 bytes - 36 pages - no figures

After his original paper on peas, Mendel published only one other paper on genetics, that one on Hieracium. These letters to Nägeli provide a rare additional glimpse into Mendel's thinking as he pursued his investigations on heredity.

Mendel, Gregor — 1869.

On Hieracium-hybrids obtained by artificial fertilisation.

Verhandlungen des naturforschenden Vereines, Abhandlungen, Brünn, Bd. VIII für das Jahr 1869, 26-31. (Translated and reprinted as an appendix to Bateson, W. 1909. Mendel's Principles of Heredity. Cambridge University Press.)

PDF typeset file: 57,344 bytes - 8 pages - no figures

After his original paper on peas, Mendel published only one other paper on genetics, this one on Hieracium. Unknown to Mendel, Hieracium does not experience normal sexual fertilization, making it impossible for him to confirm the findings that he had obtained earlier with peas.

Mendel, Gregor. — 1865.

Experiments in plant hybridization. (facsimile of first edition)

Verhandlungen des naturforschenden Vereines in Brünn, Bd. IV für das Jahr 1865, Abhandlungen, 3-47.

PDF image facsimile file: 2,142,414 bytes - 47 pages - no figures

For those wishing to see and read Mendel in the original, this provides an image facsimile of the original paper as it was published in German.

Mendel, Gregor. — 1865.

Experiments in plant hybridization.

Verhandlungen des naturforschenden Vereines in Brünn, Bd. IV für das Jahr 1865, Abhandlungen, 3-47.

PDF typeset file: 395,699 bytes - 41 pages - no figures

In February and March of 1865, Gregor Mendel presented the Brünn Natural History Society in Brünn, Czechoslovakia, with the results of his investigations into the mechanisms governing inheritance in pea plants. The next year, the work was published as Mendel, Gregor. 1866. "Versuche über Pflanzen Hybriden." Verhandlungen des naturforschenden Vereines in Brünn, 4:3-47.

In this remarkable paper, Mendel laid the groundwork for later became the science of genetics. However, the work was largely ignored when it appeared and Mendel moved on to other things. He died in 1884.

His work was rediscovered at the turn of the century and its significance immediately recognized. Genetics, as a formal scientific discipline, exploded into activity in 1900.

An annotated version of Mendel's paper is also available. The annotated version contains explanatory notes throughout the document. This can be useful to those reading Mendel's paper for the first time.

For those wishing to see and read Mendel in the original, a facsimile reprint edition is available. This version is in Adobe PDF format, but the pages are images of the original publication, not a new type-setting of the material.

You may also wish to visit The Mendel Web site, created by Roger Blumberg. The site offers many additional resources for the Mendel scholar.

Mendel, Gregor. — 1865.

Experiments in plant hybridization. (annotated)

Verhandlungen des naturforschenden Vereines in Brünn, Bd. IV für das Jahr 1865, Abhandlungen, 3-47.

PDF typeset file: 395,699 bytes - 41 pages - no figures

In February and March of 1865, Gregor Mendel presented the Brünn Natural History Society in Brünn, Czechoslovakia, with the results of his investigations into the mechanisms governing inheritance in pea plants. The next year, the work was published as Mendel, Gregor. 1866. "Versuche über Pflanzen Hybriden." Verhandlungen des naturforschenden Vereines in Brünn, 4:3-47.

In this remarkable paper, Mendel laid the groundwork for later became the science of genetics. However, the work was largely ignored when it appeared and Mendel moved on to other things. He died in 1884.

His work was rediscovered at the turn of the century and its significance immediately recognized. Genetics, as a formal scientific discipline, exploded into activity in 1900.

A non-annotated version of Mendel's paper is also available.

For those wishing to see and read Mendel in the original, a facsimile reprint edition is available. This version is in Adobe PDF format, but the pages are images of the original publication, not a new type-setting of the material.

You may also wish to visit The Mendel Web site, created by Roger Blumberg. The site offers many additional resources for the Mendel scholar.

Metz, C. W. — 1937.

Small Deficiencies and the Problem of Genetic Units in the Giant Chromosomes

Genetics, 22: 543-556.

PDF image facsimile file

Montgomery, Thos. H., Jr. — 1910.

ARE PARTICULAR CHROMOSOMES SEX DETERMINANTS?

Biological Bulletin, 19:1-17.

PDF image facsimile file

Morgan, L. V. — 1925.

Polyploidy in drosophila Melanogaster with Two Attached X Chromosomes

Genetics, 10: 148-178.

PDF image facsimile file

Morgan, L. V. — 1933.

A Closed X Chromosome in Drosophila Melanogaster

Genetics, 18: 250-283.

PDF image facsimile file

Morgan, L. V. — 1939.

A Spontaneous Somatic Exchange Between Non-homologous Chromosomes in Drosophila Melanogaster

Genetics, 24: 747-752.

PDF image facsimile file

Morgan, Thomas H. — 1909.

Are the Drone Eggs of the Honey-Bee Fertilized?

The American Naturalist 43: 316-317.

Morgan, Thomas H. — 1909.

Breeding Experiments with Rats

The American Naturalist 43: 182-185.

Morgan, Thomas H. — 1909.

Hybridology and Gynandromorphism

The American Naturalist

Morgan, Thomas H. — 1909.

Recent Experiments on the Inheritance of Coat Colors in Mice

The American Naturalist 43: 494-510.

Morgan, Thomas H. — 1909.

What are "factors" in Mendelian explanations?

American Breeders Association Reports, 5:365-369.

PDF typeset file: 108,227 bytes - 4 pages - no figures

Although T. H. Morgan is best known for heading the genetics laboratory at Columbia University (later at Cal Tech) that essentially defined American genetics research for decades, he was initially skeptical of the facile manner in which combinations of alleged Mendelian factors were being invoked to explain all manner of heritable traits.

This paper begins with a wonderful debunking of easy explanation:

In the modern interpretation of Mendelism, facts are being transformed into factors at a rapid rate. If one factor will not explain the facts, then two are invoked; if two prove insufficient, three will sometimes work out. The superior jugglery sometimes necessary to account for the result, may blind us, if taken too naïvely, to the common-place that the results are often so excellently "explained" because the explanation was invented to explain them. We work backwards from the facts to the factors, and then, presto! explain the facts by the very factors that we invented to account for them.

Morgan, Thomas H. — 1910.

Chromosomes and Heredity.

The American Naturalist, 44:449-496.

PDF typeset file: 222,436 bytes - 38 pages - one figure

Work in the laboratory of T. H. Morgan was critical in establishing that genes are real, physical entities and that they are arranged in a linear order on chromosomes. In this early, analytical paper, Morgan considers whether or not chromosomes might be carriers of the hereditary material and whether or not they might control sex determination.

Morgan's careful and logical approach is captured in his final comments on sex determination:

Science advances by carefully weighing all of the evidence at her command. When a decision is not warranted by the facts, experience teaches that it is wise to suspend judgment, until the evidence can be put to further test. This is the position we are in today concerning the interpretation of the mechanism that we have found by means of which sex is determined. I could, by ignoring the difficulties and by emphasizing the important discoveries that have been made, have implied that the problem of sex determination has been solved. I have tried rather to weigh the evidence, as it stands, in the spirit of the judge rather than in that of the advocate. One point at least I hope to have made evident, that we have discovered in the microscopic study of the germ cells a mechanism that is connected in some way with sex determination; and I have tried to show, also, that this mechanism accords precisely with that the experimental results seem to call for. The old view that sex is determined by external conditions is entirely disproven, and we have discovered an internal mechanism by means of which the equality of the sexes where equality exists is attained. We see how the results are automatically reached even if we can not entirely understand the details of the process. These discoveries mark a distinct advance in our study of this difficult problem.

Morgan, Thomas H. — 1910.

Chromosomes and heredity.

The American Naturalist, 44: 449-496.

PDF typeset file: 284,612 bytes - 38 pages - no figures

Between 1910 and 1915, work in Morgan's lab laid the foundation of the modern chromosomal theory of heredity. This paper represents Morgan's thinking early in this process.

The opening lines of his paper captures the issues that he then deemed important to a consideration of the mechanism of heredity:

We have come to look upon the problem of heredity as identical with the problem of development. The word heredity stands for those properties of the germ-cells that find their expression in the developing and developed organism. When we speak of the transmission of characters from parent to offspring, we are speaking metaphorically; for we now realize that it is not characters that are transmitted to the child from the body of the parent, but that the parent carries over the material common to both parent and offspring. This point of view is so generally accepted to-day that I hesitate to restate it. It will serve at least to show that in what I am about to say regarding heredity and the germ-cells I shall ignore entirely the possibility that characters first acquired by the body are transmitted to the germ. Were there sufficient evidence to establish this view, our problem would be affected in so far as that we should not only have to account for the way in which the fertilized egg produces the characters of the adult, but also for the way in which the characters of the adult modify the germ-cells. The modern literature of development and heredity is permeated through and through by two contending or contrasting views as to how the germ produces the characters of the individual. One school looks upon the egg and sperm as containing samples or particles of all the characters of the species, race, line, or even of the individual. This view I shall speak of as the particulate theory of development. The other school interprets the egg or sperm as a kind of material capable of progressing in definite ways as it passes through a series of stages that we call its development. I shall call this view the theory of physico-chemical reaction, or briefly the reaction theory.

Morgan, Thomas H. — 1910.

Sex-limited inheritance in Drosophila.

Science, 32:120-122.

PDF typeset file: 72,823 bytes - 14 pages - no figures

After Mendel's work was rediscovered in 1900, many researchers worked to confirm and extend his findings. Although a possible relationship between genes and chromosomes was suggested almost immediately, proof of that relationship, or even evidence that genes were physical objects, remained elusive. To many, the gene served only as a theoretical construct, conveniently invoked to explain observed inheritance patterns. In 1909, Morgan himself published a paper in which he expressed his skepticism about the facility with which Mendelian explanations were adjusted to fit the facts.

Just one year later, however, Morgan published the results of his work on an atypical male fruit fly that appeared in his laboratory, and all this began to change. Normally Drosophila melanogaster have red eyes, but Morgan's new fly had white eyes. The inheritance pattern for this new eye-color trait suggested strongly that the gene for eye-color was physically attached to the X-chromosome. In the paper, Morgan concluded:

It now becomes evident why we found it necessary to assume a coupling of [the eye-color gene] and X in one of the spermatozoa of the red-eyed F1 hybrid. The fact is that this R and X are combined, and have never existed apart.

In this present paper, Morgan offered the first evidence that genes are real, physical objects, located on chromosomes, with properties that could be manipulated and studied experimentally. The white-eyed fly provided the foundation upon which Morgan and his students established the modern theory of the gene.

Morgan, Thomas H. — 1911.

Chromosomes and associative inheritance.

Science, New Series, 34:636-638.

PDF image facsimile file: 613,691 bytes - 3 pages - 0 figures

Morgan, Thomas H. — 1911.

Random segregation versus coupling in Mendelian inheritance

Science, 34:384.

PDF image facsimile file: 189,193 bytes - 1 page

Morgan, Thomas H. — 1911.

The origin of five mutations in eye color in Drosophila and their modes of inheritance.

Science, New Series, 33:534-537.

PDF image facsimile file: 694,626 bytes - 4 pages - 0 figures

Morgan, Thomas H. — 1911.

The origin of nine wing mutations in Drosophila.

Science, New Series, 33:496-499.

PDF image facsimile file: 688,689 bytes - 4 pages - 0 figures

Morgan, Thomas H. — 1912.

Complete linkage in the second chromosome of the male of Drosophila

Science, 36:933-934.

PDF image facsimile file: 325,825 bytes - 2 pages

Morgan, Thomas H. — 1913.

Factors and Unit Characters in Mendelian Heredity.

The American Naturalist, 47:5-16.

PDF image facsimile file: 741,353 bytes - 14 pages - 0 figures

Morgan, Thomas H. — 1913.

Simplicity versus adequacy in Mendelian formulae

The American Naturalist, 47:372-374

PDF typeset file: 32,835 bytes - 6 pages - no figures

Soon after Mendel was rediscovered, the nature of the gene was being worked out. Along the way, many suggested changes to the symbology being used (e.g., B for dominant allele, b for recessive). Here Morgan offers some thoughts on changing Mendelian symbols.

Morgan, Thomas H. — 1915.

The Constitution of the Hereditary Material.

Proceedings of the American Philosophical Society, 54:143-153.

PDF image facsimile file: 424,504 bytes - 11 pages - 4 figures

Morgan, Thomas H. — 1917.

The Theory of the Gene.

The American Naturalist, 51:513-544.

PDF typeset file: 3,116,439 bytes - 28 pages - 9 figures

In 1909, Morgan expressed doubts about the methods of Mendelian inheritance. Then, in 1910, a white-eyed mutant fly turned up in Morgan’s laboratory and studies on the inheritance of the white-eyed trait suggested that the gene producing the trait was carried on the X-chromosome. This strongly suggested that Mendelian genes were real, not th The Mechanism of Mendelian Heredity.

In this paper, Morgan discusses The Theory of the Gene, as established in his laboratory.

Morgan, Thomas H. — 1919.

The Physical Basis of Heredity.

Philadelphia: J. B. Lippincott Company

This is a full-text PDF image facsimile version of the entire 305-page original book.

In this book, T. H. Morgan (who would later receive the first Nobel Prize for genetics research) describes the model of heredity developed at Columbia by Morgan and his students.

The foundations of genetics were laid down by Mendel, and these were brought to the world's attention when his work was rediscovered by Correns, de Vries, and von Tschermak in 1900. But the real establishment of genetics as a real science, with a known physical basis, did not occur until the work outlined in this book became generally known.

To understand the true conceptual underpinnings of classical genetics, one must read the publications from "The Fly Room" at Columbia.

Morgan, Thomas H. — 1922.

Croonian Lecture: On the Mechanism of Heredity.

Proceedings of the Royal Society, B, 94:162-197.

PDF typeset file: 3,916,605 bytes - 42 pages - 35 figures

The Croonian Lecture is the Royal Society's premier lecture in the biological sciences. Dr Croone, one of the original members of the Society, left on his death in 1684 a scheme for two lectureships, one at the Royal Society and the other at the Royal College of Physicians

Morgan was invited to give the Croonian lecture in 1922 - a recognition of his pioneering work in elucidating the physical basis of heredity.

Morgan, Thomas H. — 1923.

The bearing of Mendelism on the origin of species.

The Scientific Monthly, 16: 237-247.

PDF typeset file: 247,951 bytes - 54 pages - no figures

In December of 1922, the American Society of Naturalists held a special session to honor the centenaries of the birth of Gregor Mendel and of Francis Galton. This is one of the four papers presented at that session and later published in the The Scientific Monthly.

Morgan, Thomas H. — 1928.

The Theory of the Gene, Revised and Enlarged Edition.

New Haven: Yale University Press

This is a full-text PDF image facsimile version of the entire 358-page original book.

This book, by T. H. Morgan, summarizes the state of knowledge on classical genetics in the mid 1920's.

Although Mendelism had quickly been accepted as a good phenomenological explanation for the patterns seen in Mendelian crosses, until the work of Morgan's group, it was still possible to consider Mendelism to be a purely theoretical model of heredity. As Morgan's group first established the relationship of genes to chromosomes, then developed the first genetic map, and went on to describe a variety of interactions between chromosomes and Mendelian factors, the conclusions they offered became inescapable – genes are physical objects, carried on chromosomes in static locations.

Less than 15 years after Morgan first started working with fruit flies, the foundations for a theory of the gene had been worked out – largely by Morgan and students working in his laboratory.

Morgan, Thomas H., Sturtevant, A. H., Muller, H. J., and C. B. Bridges — 1915.

The Mechanism of Mendelian Heredity.

New York: Henry Holt and Company

This is a full-text PDF image facsimile version of the entire 262-page original book.

This book, by T. H. Morgan and his students, is the first work to articulate a comprehensive, mechanistic model to explain Mendelian patterns of inheritance.

Although Mendelism had quickly been accepted as a good phenomenological explanation for the patterns seen in Mendelian crosses, until the work of Morgan's group, it was still possible to consider Mendelism to be a purely theoretical model of heredity. As Morgan's group first established the relationship of genes to chromosomes, then developed the first genetic map, and went on to describe a variety of interactions between chromosomes and Mendelian factors, the conclusions they offered became inescapable - genes are physical objects, carried on chromosomes in static locations.

Morgan's group made genes real and this book is the first full-length presentation of their findings. It revolutionized the study of heredity.

Morgan, Thomas Hunt — 1897.

The Development of the Frog's Egg: An Introduction to Experimental Embryology.

New York: The Macmillan Company

PDF image facsimile file: 46,153,994 bytes - 204 pages - several figures

Thomas Hunt Morgan is best known for his work in genetics, for which he received the Nobel Prize in 1933. Morgan's first research interest, however, was in embryology. This short book on frog development is his first book.

From the Preface: The development of the frog's egg was first made known through the studies of Swammerdam, Spallanzani, Rusconi, and von Baer. Their work laid the basis for all later research. More recently the experiments of Pfluger and of Roux on this egg have turned the attention of embryologists to the study of development from an experimental standpoint. Owing to the ease with which the frog's egg can be obtained, and its tenacity of life in a confined space, as well as its suitability for experimental work, it is an admirable subject with which to begin the study of vertebrate development. In the following pages an attempt is made to bring together the most important results of studies of the development of the frog's egg. I have attempted to give a continuous account of the development, as far as that is possible, from the time when the egg is forming to the moment when the young tadpole issues from the jelly-membranes. Especial weight has been laid on the results of experimental work, in the belief that the evidence from this source is the most instructive for an interpretation of the development. The evidence from the study of the normal development has, however, not been neglected, and wherever it has been possible I have attempted to combine the results of experiment and of observation, with the hope of more fully elucidating the changes that take place. Occasionally departures have been made from the immediate subject in hand in order to consider the results of other work having a close bearing on the problem under discussion. I have done this in the hope of pointing out more definite conclusions than could be drawn from the evidence of the frog's egg alone.

Müller, F. — 1869.

Facts and Arguments for Darwin.

London: John Murray, Albemarle Street

Johann Friedrich Theodor Müller (March 31, 1821 – May 21, 1897), always known as Fritz, was a German biologist and physician who emigrated to southern Brazil, where he lived in and near the German community of Blumenau, Santa Catarina. There he studied the natural history of the Atlantic forest south of São Paulo, and was an early advocate of Darwinism. He lived in Brazil for the rest of his life. Müllerian mimicry is named after him.

Müller became a strong supporter of Darwin. He wrote Für Darwin in 1864, arguing that Charles Darwin's theory of evolution by natural selection was correct, and that Brazilian crustaceans and their larvae could be affected by adaptations at any growth stage. This was translated into English by W.S. Dallas as Facts and Arguments for Darwin in 1869 (Darwin sponsored the translation and publication). If Müller had a weakness it was that his writing was much less readable than that of Darwin or Wallace; both the German and English editions are hard reading indeed, which has limited the appreciation of this significant book.

Muller, H. J. and Jacobs-Muller, Jessie M. — 1925.

The Standard Errors of Chromosome Distances and Coincidence

Genetics, 10: 509-524.

PDF image facsimile file

Muller, H. J., Raffel, D., Gershenson, S. M. , and Prokofyeva-Belgovskaya, A. A. — 1937.

A Further Analysis of Loci in the So-called "inert Region" of the X Chromosome of Drosophila

Genetics, 22: 87-93.

PDF image facsimile file

Muller, Hermann J. — 1916.

The Mechanism of Crossing-over.

New York: The American Naturalist

This is an image facsimile version of the entire 86-page original edition.

Beginning 1910, T. H. Morgan and his students established the foundations of modern genetics by demonstrating that genes were real — not theoretical — entities.

This work is a collection of papers that represented the doctoral dissertation of one of those students - H. J. Muller.

Muller, Hermann J. — 1918.

Genetic Variability, Twin Hybrids and Constant Hybrids, in a Case of Balanced Lethal Factors

Genetics, 3: 422-499.

PDF image facsimile file

Muller, Hermann J. — 1918.

Genetic variability, twin hybrids and constant hybrids, in a case of balanced lethal factors.

Genetics, 3:422-499.

PDF image facsimile file: 78 pages

Muller, Hermann J. — 1922.

Variation due to change in the individual gene.

The American Naturalist, 56:32-50.

PDF typeset file: 69,751 bytes - 17 pages - no figures

This paper is from an address given by to the thirty-ninth annual meeting of the American Society of Naturalists, held in Toronto on 29 December 29 1921.

In this remarkably prescient analysis, Muller lays out the paradoxical nature of the genetic material. It is apparently both autocatalytic (i.e., directs its own synthesis) and heterocatalytic (i.e., directs the synthesis of other molecules), yet only the heterocatalytic function seems subject to mutation. With this, he defines the key problems that must be solved for a successful chemical model of the gene.

Muller also anticipated the ultimate development of molecular genetics:

That two distinct kinds of substances — the d'Hérelle substances (NOTE: viruses) and the genes — should both possess this most remarkable property of heritable variation or "mutability," each working by a totally different mechanism, is quite conceivable, considering the complexity of protoplasm, yet it would seem a curious coincidence indeed. It would open up the possibility of two totally different kinds of life, working by different mechanisms. On the other hand, if these d'Hérelle bodies were really genes, fundamentally like our chromosome genes, they would give us an utterly new angle from which to attack the gene problem. They are filterable, to some extent isolable, can be handled in test tubes, and their properties, as shown by their effects on the bacteria, can then be studied after treatment. It would be very rash to call these bodies genes, and yet at present we must confess that there is no distinction known between the genes and them. Hence we cannot categorically deny that perhaps we may be able to grind genes in a mortar and cook them in a beaker after all. Must we geneticists become bacteriologists, physiological chemists and physicists, simultaneously with being zoologists and botanists? Let us hope so.

Muller, Hermann J. — 1925.

The regionally differential effect of X rays on crossing over in autosomes of Drosophila.

Genetics, 10:470-507.

PDF image facsimile file: 38 pages

Muller, Hermann J. — 1927.

Artificial transmutation of the gene.

Science, 46:84-87.

PDF image facsimile file: 1,002,392 bytes - 4 pages

Muller, Hermann J. — 1928.

The measurement of gene mutation rate in Drosophila, its high variability, and its dependence upon temperature.

Genetics, 13:279-357.

PDF image facsimile file: 79 pages

Muller, Hermann J., Raffel, D., Gershenson, S. M., and Prokofya-Belgovskaya, A. A. — 1937.

A further analysis of loci in the so-called "inert region" of the X chromosome of Drosophila.

Genetics, 22:87-93.

PDF image facsimile file: 7 pages

Muller, Hermann J., and Altenburg, Edgar. — 1930.

The frequency of translocations produced by X-rays in Drosophila.

Genetics, 15:283-311.

PDF image facsimile file: 29 pages

Muller, Hermann J., and Jacobs-Muller, Jessie M. — 1925.

The standard errors of chromosome distances and coincidence.

Genetics, 10:509-524.

PDF image facsimile file: 16 pages

Painter, Theophilus S. — 1928.

A Comparison of the Chromosomes of the Rat and Mouse with Reference to the Question of Chromosome Homology in Mammals

Genetics, 13: 180-189.

PDF image facsimile file

Painter, Theophilus S. and Griffen, Allen B. — 1937.

The Structure and the Development of the Salivary Gland Chromosomes of Simulium

Genetics, 22: 612-633.

PDF image facsimile file

Painter, Theophilus S. and Stone, Wilson — 1935.

Chromosome Fusion and Speciation in Drosophilae

Genetics, 20: 327-341.

PDF image facsimile file

Painter, Theophilus S. — 1934.

A New Method For the Study of Chromosome Aberrations and the Plotting of Chromosome Maps in Drosophila melanogaster.

Genetics, 19: 175-188.

PDF image facsimile file: 915,967 bytes - 14 pages - 2 figures

Now, almost any reference to the genetics of Drosophila includes some illustration of the giant salivary gland chromosomes found in these flies. Although Drosophila had been used effectively since 1910, it was this paper by Painter that first showed the tremendous potential of these chromosomes for cytogenetic research. New discovery often hinges on new methods and this paper is truly a break-through study in genetic methodology.

Painter, Theophilus S. — 1934.

The Morphology of the X Chromosome in Salivary Glands of Drosophila melanogaster and a New Type of Chromosome Map for this Element.

Genetics, 19: 448-469.

PDF image facsimile file: 1,519,775 bytes - 22 pages - 2 figures

In this paper, Painter follows up on his earlier publication describing Drosophila giant salivary-gland chromosomes and here shows how genetics maps, obtained from crossing studies, can be placed on a morphological map obtained from cytological studies.

Patterson, J. T. and Muller, H. J. — 1930.

Are "progressive" mutations produced by X-rays?

Genetics, 15: 495-577.

PDF image facsimile file

Patterson, J. T. — 1933.

The Mechanism of Mosaic Formation in Drosophila

Genetics, 18: 32-52.

PDF image facsimile file

Payne, F. — 1924.

Crossover Modifiers in the Third Chromosome of Drosophila melanogaster

Genetics, 9: 327-342.

PDF image facsimile file

Plough, Harold H. and Ives, Philip T. — 1935.

Induction of Mutations by High Temperature in Drosophila

Genetics, 20: 42-69.

PDF image facsimile file

Powers, J. H. — 1909.

Are Species Realities or Concepts Only?

The American Naturalist

Punnett, R. C. — 1905.

Mendelism, 1st Edition.

Cambridge: Bowes and Bowes

PDF image facsimile file: 1,382,040 bytes - 71 pages - several figures

This little book is the first edition of the first genetics textbook ever written. It was published just five years after Mendel's work was rediscovered.

Punnett, R. C. — 1907.

Mendelism, 2nd Edition.

Cambridge: Bowes and Bowes

PDF image facsimile file: 1,832,735 bytes - 93 pages - several figures

This second edition of Punnett's text on Mendelism came out just two years after the first edition. In this new edition, Punnett Squares appeared for the first time. Also, the author included an index (that could fit on a single page with room left over).

Rhoades, Marcus M. — 1933.

An Experimental and Theoretical Study of Chromatid Crossing Over

Genetics, 18: 535-555.

PDF image facsimile file

Riddle, Oscar. — 1924.

Any Hereditary Character and the Kinds of Things We Need to Know About It.

The American Naturalist, LVIII:410-425.

PDF typeset file: 80,148 bytes - 13 pages - no figures

This does not qualify as a classic genetics paper and I suspect that it has never before been included in a collection of important papers. However, it is included here because it provides a glimpse into some general aspects of genetic thought in the mid 1920's.

The premise of this essay is essentially that, as of its writing, " studies on heredity and evolution offer what is mainly a two-sided attack on a many-sided problem." This argument was well taken, but the modern reader may have difficulty appreciating other concerns of the essay.

Schultz, Jack — 1929.

The minute reaction in the development of Drosophila melanogaster

Genetics, 14: 366-419.

PDF image facsimile file

Schultz, Jack — 1933.

X-ray Effects on Drosophila Pseudo-obscura

Genetics, 18: 284-291.

PDF image facsimile file

Schultz, Jack, and Dobzhansky, Th. — 1934.

The Relation of a Dominant Eye Color in Drosophila Melanogaster to the Associated Chromosome Rearrangement

Genetics, 19: 344-364.

PDF image facsimile file

Shull, A. Franklin — 1922.

Ten Years of Heredity.

Transactions of the American Microscopical Society, 41:82-100.

PDF image facsimile file: 909,722 bytes - 19 pages - 8 figures

Shull, G. H. — 1915.

Genetic Definitions in the New Standard Dictionary.

The American Naturalist, 49:52-59.

PDF typeset file: 78,002 bytes - 12 pages - no figures

In this short paper, Shull takes exception to some recently published dictionary definitions of many technical genetics terms and he offers corrected definitions in their stead. The main value of this paper to modern readers is that it gives a very good idea of what geneticists (or at least this geneticist) meant by their use of genetic terminology at the time. Although many of Shull's proffered definitions would be at home in a modern biology text, some are no longer in current usage.

Shull could have done a better job of defining "alternative inheritance" by adding "contrast with continuous inheritance," since at the time of his writing there was still a school of thought that argued that most heritable variation was continuous but that Mendelian theories provided explanations only for cases of "alternative inheritance," which were rare in nature and might only represent artifacts of inheritance in domesticated organisms.

For just such a criticism of alternative inheritance, see Weldon, W. F. R. 1902 Mendel's laws of alternative inheritance in peas. Biometrika, 1:228-254.

Shull, George H. — 1923.

A permanent memorial to Galton and Mendel.

The Scientific Monthly, 16: 263-270.

PDF typeset file: 247,951 bytes - 54 pages - no figures

In December of 1922, the American Society of Naturalists held a special session to honor the centenaries of the birth of Gregor Mendel and of Francis Galton. This is one of the four papers presented at that session and later published in the The Scientific Monthly.

Shull, George Harrison — 1909.

The "Presence and Absence" Hypothesis.

The American Naturalist, 43:410-419.

PDF image facsimile file: 655,705 bytes - 10 pages - 0 figures

Sivertzev-Dobzhansky, N. P. and Dobzhansky, Th. — 1933.

Deficiency and Duplications For the Gene Bobbed in Drosophila Melanogaster

Genetics, 18: 413.

PDF image facsimile file

Snyder, Laurence H. — 1924.

The Inheritance of the Blood Groups

Genetics, 9: 465-478.

PDF image facsimile file

Spillman, W. J. — 1908.

Spurious Allelomorphism: Results of Some Recent Investigations

The American Naturalist

Spillman, W. J. — 1909.

A Case of Non-Mendelian Heredity

The American Naturalist 43: 437-448.

Spillman, W. J. — 1909.

The Nature of "Unit" Characters

The American Naturalist 43: 243-248.

Stadler, L. J. — 1926.

The Variability of Crossing Over in Maize

Genetics, 11: 1-37.

PDF image facsimile file

Stern, Curt and Bridges, Calvin B. — 1926.

The Mutants of the Extreme Left End of the Second Chromosome of Drosophila melanogaster

Genetics, 11: 503-530.

PDF image facsimile file

Stevens, Nettie M. — 1905.

Studies in Spermatogenesis with especial reference to the "accessory chromosome".

Carnegie Institution of Washington, Publication No. 36., pp 1-33.

PDF image facsimile file: 1,448,192 bytes - 33 pages - 7 plates

Stevens, Nettie M. — 1906.

Studies in Spermatogenesis Part II., A comparative study of the heterochromosomes in certain species of coleoptera, hemiptera and lepidoptera, with especial reference to sex determination.

Carnegie Institution of Washington, Publication No. 36, part II., pp 1-43.

PDF image facsimile file: 1,936,652 bytes - 43 pages - 8 plates

Stevens, Nettie M. — 1906.

Studies on the germ cells of aphids.

Carnegie Institution of Washington, Publication No. 51., pp 1-28.

PDF image facsimile file: 1,180,954 bytes - 28 pages - 4 plates

Sturtevant, A. H. and Beadle, G. W. — 1936.

The Relations of Inversions in the X Chromosome of Drosophila Melanogaster to Crossing Over and Disjunction

Genetics, 21: 554-604.

PDF image facsimile file

Sturtevant, A. H. and Dobzhansky, Th. — 1936.

Geographical Distribution and Cytology of "sex Ratio" in Drosophila Pseudoobscura and Related Species

Genetics, 21: 473-490.

PDF image facsimile file

Sturtevant, A. H. — 1917.

Crossing Over without Chiasmatype?

Genetics, 2:301-304.

PDF image facsimile file: 220,991 bytes - 4 pages - no figures

Sturtevant, A. H. — 1928.

A Further Study of the So-call Mutation at the Bar Locus of Drosophila

Genetics, 13:401-409

PDF image facsimile file

Sturtevant, A. H. — 1936.

Preferential Segregation in Triplo-IV Females of Drosophila Melanogaster

Genetics, 21: 444-466.

PDF image facsimile file

Sturtevant, A. H., Bridges, C. B., and Morgan, T. H. — 1919.

The spatial relations of genes.

Proceedings of the National Academy of Sciences, 5:168-173.

PDF image facsimile file: 727,921 bytes - 6 pages

Sturtevant, Alfred H. — 1965.

A History of Genetics.

First published in 1965, it was brought back into print in 2001 by Cold Spring Harbor Laboratory Press and the Electronic Scholarly Publishing project.

This is a full-text PDF typeset version of the entire 167-page original book.

Between 1910 and 1915, the modern chromosomal theory of heredity was established, largely through work done in the laboratory of Thomas H. Morgan at Columbia University. This book, by one of Morgan's students, presents the history of early genetics and captures the excitement as a new discipline was being born.

Sturtevant himself made major contributions to genetics, including the development of the world's first genetic map in 1913.

Sturtevant, Alfred H. — 1913.

The linear arrangement of six sex-linked factors in Drosophila, as shown by their mode of association.

Journal of Experimental Biology, 14:43-59.

PDF typeset file: 109,620 bytes - 22 pages - no figures

In 1998, with genome projects routinely producing detailed genetics maps of mice and men and every other sort of organism, it can be difficult to imagine a time when there were no genetic maps. The idea that individual genes occupy regular positions on chromosomes was one of the great insights of early genetics, and the very first genetic map was published in 1913 by Alfred H. Sturtevant, who was working on fruit flies in the laboratory of Thomas H. Morgan at Columbia University.

Sturtevant is now well known as one of the most important early pioneers in genetic research. However, at the time he produced the first map, he was an undergraduate. Many years later, Sturtevant (A History of Genetics) described how an undergraduate came to be crucially involved in establishing the very foundations of classical genetics:

In 1909, the only time during his twenty-four years at Columbia, Morgan gave the opening lectures in the undergraduate course in beginning zoology. It so happened that C. B. Bridges and I were both in the class. While genetics was not mentioned, we were both attracted to Morgan and were fortunate enough, though both still undergraduates, to be given desks in his laboratory the following year (1910-1911). The possibilities of the genetic study of Drosophila were then just beginning to be apparent; we were at the right place at the right time. In the latter part of 1911, in conversation with Morgan, I suddenly realized that the variations in strength of linkage, already attributed by Morgan to differences in the spatial separation of the genes, offered the possibility of determining sequences in the linear dimension of a chromosome. I went home and spent most of the night (to the neglect of my undergraduate homework) in producing the first chromosome map, which included the sex-linked genes y, w, v, m, and r, in the order and approximately the relative spacing that they still appear on the standard maps (Sturtevant, 1913).

Sturtevant, Alfred H. — 1913.

The linear arrangement of six sex-linked factors in Drosophila, as shown by their mode of association.

Journal of Experimental Biology, 14:43-59.

PDF typeset file: 109,620 bytes - 22 pages - no figures

In 1998, with genome projects routinely producing detailed genetics maps of mice and men and every other sort of organism, it can be difficult to imagine a time when there were no genetic maps. The idea that individual genes occupy regular positions on chromosomes was one of the great insights of early genetics, and the very first genetic map was published in 1913 by Alfred H. Sturtevant, who was working on fruit flies in the laboratory of Thomas H. Morgan at Columbia University.

Sturtevant is now well known as one of the most important early pioneers in genetic research. However, at the time he produced the first map, he was an undergraduate. Many years later, Sturtevant (A History of Genetics) described how an undergraduate came to be crucially involved in establishing the very foundations of classical genetics:

In 1909, the only time during his twenty-four years at Columbia, Morgan gave the opening lectures in the undergraduate course in beginning zoology. It so happened that C. B. Bridges and I were both in the class. While genetics was not mentioned, we were both attracted to Morgan and were fortunate enough, though both still undergraduates, to be given desks in his laboratory the following year (1910-1911). The possibilities of the genetic study of Drosophila were then just beginning to be apparent; we were at the right place at the right time. In the latter part of 1911, in conversation with Morgan, I suddenly realized that the variations in strength of linkage, already attributed by Morgan to differences in the spatial separation of the genes, offered the possibility of determining sequences in the linear dimension of a chromosome. I went home and spent most of the night (to the neglect of my undergraduate homework) in producing the first chromosome map, which included the sex-linked genes y, w, v, m, and r, in the order and approximately the relative spacing that they still appear on the standard maps (Sturtevant, 1913).

Sturtevant, Alfred H. — 1920.

Genetic studies on Drosophila simulans. I. Introduction. Hybrids with Drosophila melanogaster.

Genetics, 5:488-500.

PDF image facsimile file: 13 pages - 5 figures

Sturtevant, Alfred H. — 1921.

Genetic studies on Drosophila simulans. II. Sex-linked groups of genes.

Genetics, 6:43-64.

PDF image facsimile file: 22 pages - 5 figures

Sturtevant, Alfred H. — 1921.

Genetic studies on Drosophila simulans. III. Autosomal genes. General discussion.

Genetics, 6:179-207.

PDF image facsimile file: 29 pages - 6 figures

Sturtevant, Alfred H. — 1923.

Inheritance of the direction of coiling in Limnaea.

Science, 58:269-270.

PDF typeset file: 150,314 bytes - 7 pages - no figures

As evidence mounted for the chromosomal basis of inheritance, occasional examples were discovered that seemed to challenge the Mendelian model, as mapped to the chromosomes by T. H, Morgan and his students. In this paper, A. H. Sturtevant (one of Morgan's students) shows that apparently aberrant patterns of inheritance can be seen to correspond to the Mendelian model, if care is taken to assign phenotype to the correct individual.

The case in question is the direction of shell coiling in snails of the genus Limnaea. These shells can either coil to the right (dextral) or left (sinistral). Coiling seemed to be an inherited trait, except that the observed patterns of inheritance were strange. Broods of offspring from sinistral snails, produced by self-fertilization (these snails are hermaphroditic) were either all sinistral or all dextral (never some of each). The same was found true if the single parent was dextral. Complicated models had been offered to explain these results, but here Sturtevant shows that a much simpler model is equally effective:

An analysis of the data presented suggests that the case is a simple Mendelian one, with the dextral character dominant, but with the nature of a given individual determined, not by its own constitution but by that of the unreduced egg from which it arose.

A similar problem exists with the color of bird eggs. Chickens, for example, can produce eggs that are either brown or white, and these colors are genetically determined. However, the trait "shell color" is an attribute of the hen laying the eggs, not of the chick that hatches out of the egg. When you realize that the shell is created as a secretion in the hen's oviducts, this makes perfect sense, even though the actual egg shell is ultimately separate from the body of the hen and is part of the egg from which the chick hatches.

The direction of shell coiling is now known to be controlled by specific proteins present in the cytoplasm of the egg. These proteins are produced early in egg development, prior to fertilization, and so are produced solely from genes present in the mother. Just as with the color of egg shells in chickens, the direction of shell coiling in Limnaea is really part of the phenotype of the mother of the snail, not of the snail actually wearing the shell.

Sturtevant, Alfred H. — 1925.

The effects of unequal crossing over at the bar locus in Drosophila.

Genetics, 10:117-147.

PDF image facsimile file: 31 pages - 10 figures

Sturtevant, Alfred H. — 1928.

A further study of the so-called mutation at the bar locus of Drosophila.

Genetics, 13:401-409.

PDF image facsimile file: 9 pages - no figures

Sutton, Walter S. — 1902.

On the morphology of the chromosome group in Brachystola magna.

Biological Bulletin, 4:24-39.

PDF typeset file: 119,906 bytes - 18 pages - 11 figures

In this paper, Sutton reports cytological studies of grasshopper chromosomes that lead him to conclude that (a) chromosomes have individuality, (b) that they occur in pairs, with one member of each pair contributed by each parent, and (c) that the paired chromosomes separate from each other during meiosis.

After presenting considerable evidence for his assertions, Sutton closes his paper with a sly reference to its undoubted significance:

I may finally call attention to the probability that the association of paternal and maternal chromosomes in pairs and their subsequent separation during the reducing division as indicated above may constitute the physical basis of the Mendelian law of heredity. To this subject I hope soon to return in another place.

Sutton, Walter S. — 1903.

The chromosomes in heredity.

Biological Bulletin, 4: 231-251.

PDF typeset file: 133,686 bytes - 20 pages - no figures

Early on, some researchers noticed that Mendel's theory required that some kind of hereditary unit segregate in pairs to offspring. Sutton was one of the first to note that the chromosomes behaved in exactly a manner to match this requirement.

The opening lines of his paper show that he is aware of the significance of his observations:

In a recent announcement of some results of a critical study of the chromosomes in the various cell generations of Brachystola the author briefly called attention to a possible relation between the phenomena there described and certain conclusions first drawn from observations on plant hybrids by Gregor Mendel in 1865, and recently confirmed by a number of able investigators. Further attention has already been called to the theoretical aspects of the subject in a brief communication by Professor E. B. Wilson. The present paper is devoted to a more detailed discussion of these aspects, the speculative character of which may be justified by the attempt to indicate certain lines of work calculated to test the validity of the conclusions drawn. The general conceptions here advanced were evolved purely from cytological data, before the author had knowledge of the Mendelian principles, and are now presented as the contribution of a cytologist who can make no pretensions to complete familiarity with the results of experimental studies on heredity. As will appear hereafter, they completely satisfy the conditions in typical Mendelian cases, and it seems that many of the known deviations from the Mendelian type may be explained by easily conceivable variations from the normal chromosomic processes.

Taliaferro, W. H., and Huck, J. G. — 1923.

The Inheritance of Sickle-cell Anaemia in Man

Genetics, 8: 594-598.

PDF image facsimile file

Tan, C. C. — 1936.

Genetic Maps of the Autosomes in Drosophila Pseudoobscura

Genetics, 21: 796-807.

PDF image facsimile file

Thompson, David H. — 1931.

The side-chain theory of the structure of the Gene

Genetics, 16: 267-290.

PDF image facsimile file

Thomson, J. Arthur. — 1908.

Heredity.

London: John Murray

This is a PDF image facsimile version of the entire 596-page original first edition.

This book is one of the first textbook treatments of heredity after the rediscovery of Mendel's work. Thomson provides his analysis in the context of the understanding of inheritance in the pre-Mendelian late nineteenth century. Chapter 11, History of Theories of Heredity and Inheritance summarizes many of the nineteenth-century theories of heredity.

In his bibliography, Thomson cites many nineteenth-century works. He also provides a subject-index to the bibliography, making this collection of citations especially valuable.

Tschermak, Erik von — 1900.

Concerning artificial crossing in Pisum sativum

First published in English as: Tschermak, E. 1950. Concerning artificial crossing in Pisum sativum. Genetics, 35(5, pt 2): 42-47. Originally published as: Tschermak, E. 1900. Über Künstliche Kreuzung bei Pisum sativum. Berichte der Deutsche Botanischen Gesellschaft 18: 232-239, 1900.

PDF typeset file: 62,114 bytes - 10 pages - no figures

Tschermak, along with Carl Correns and Hugo de Vries, is considered to be one of the three co-discovers of Mendel's work in 1900. He had been working himself with garden peas when he rediscovered Mendel's prior contributions. In a postscript to his paper, he wrote:

Correns has just published experiments which also deal with artificial hybridization of different varieties of Pisum sativum and observations of the hybrids left to self-fertilization through several generations. They confirm, just as my own, Mendel's teachings. The simultaneous "discovery" of Mendel by Correns, de Vries, and myself appears to me especially gratifying. Even in the second year of experimentation, I too still believed that I had found something new.

Vries, Hugo De — 1925.

Mutant Races Derived from Oenothera Lamarckiana Semigigas

Genetics, 10: 211-222.

PDF image facsimile file

Vries, Hugo de — 1900.

Concerning the law of segregation of hybrids.

First published in English as: De Vries, H.. 1950. Concerning the law of segregation of hybrids. Genetics, 35(5, pt 2): 30-32. Originally published as: De Vries, H. 1900. Sur la loi de disjonction des hybrides. Comptes Rendus de l'Academie des Sciences (Paris), 130: 845-847.

PDF typeset file: 35,435 bytes - 6 pages - no figures

Hugo de Vries, along with Carl Correns and Erik von Tschermak, is considered to be one of the three co-discovers of Mendel's work in 1900. De Vries was by far the most established scientist at the time, with an established research record dealing with "mutations" (variations) and speciation.

In this first of two papers that he published in 1900, de Vries does not even mention Mendel by name, even though he adopts Mendelian terminology such as dominant and recessive.

Vries, Hugo de — 1918.

Mutations of Oenothera suaveolens desf.

Genetics, 3:1-26.

PDF image facsimile file: 26 pages

Vries, Hugo de — 1918.

Twin hybrids of Oenothera hookeri T. and G..

Genetics, 3:397-421.

PDF image facsimile file: 25 pages

Vries, Hugo de — 1925.

Mutant races derived from Oenothera lamarckiana semigigas.

Genetics, 10:211-222.

PDF image facsimile file: 12 pages

Vries, Hugo de, and Boedijn, K. — 1923.

On the distribution of mutant characters among the chromosomes of Oenothera lamarckiana.

Genetics, 8:233-238.

PDF image facsimile file: 6 pages

Vries, Hugo de. — 1910.

Intracellular Pangenesis.

Chicago: The Open Court Publishing Co.

This is a full-text PDF image facsimile version of the entire 270-page original book

This classic work, first published in German in 1889, presents De Vries's theory of the pangen, a morphological structure carrying hereditary material. The name "gene," later coined by Johannsen, was derived from de Vries's pangen.

Hugo De Vries is often now remembered, along with Correns and von Tschermak, primarily for their role in the rediscovery of Mendel in 1900. Of the three, however, De Vries was by far the most established scientist. He was one of the most well-known botanists in Europe and had already been developing his own theoretical model of heredity - intracellular pangenesis.

Intracellular pangenesis was based on Darwins's concept of pangenesis as presented in chapter 27 of his massive, two-volume The Variation of Animals and Plants under Domestication. De Vries view, however, has a more modern feel than Darwin's, as De Vries thought about the inheritance of individual characters (as did Mendel), not just about more general overall species characteristics. De Vries called his units of inheritance pangens and later he came to believe that a pangen for a particular trait was the same, no matter in which species it occurred. This is an interesting anticipation of what would later be seen as genetic homology.

Waldeyer, W. — 1888.

Über Karyokinese und ihre Beziehungen zu den Befruchtungsvorgängen, I (On karyokinesis and its relation to the process of fertilization, I).

Archiv für mikroskopische Anatomie und Entwicklungsmechanik, 32:1-122.

PDF image facsimile file

In this review, Waldeyer summarizes the recent major advances in cytology that had occurred up to the date of his paper (1888). Then he proposes a new term — chromosome: Wir haben nun noch einige Punkte genauer zu besprechen, die bi den Vorschlag erlauben, diejenigen Dinge, welche soeben mit Boveri als "chromatische Elemente" bezeichnet wurden, an denen sieh einer der wichtigsten Akte der Karyokinese, die Flemming'sche Längstheilung vollzieht, mit einem besonderen terminus technicus "Chromosomen" zu belegen. Der Name "primäre Schleifen" passt nicht, da wir bei weitem nicht immer eine Schleifenform für diese Dinge haben. "Chromatische Elemente" ist zu lang. Andererseits sind sie so wichtig, dass ein besonderer küzerer Name wünschenswerth erscheint. Platner (160) gebraucht den Ausdruck "Karyosomen"; da dieser aber zu sehr an Kernkörperchen erinnert, dürfte eine andere Bezeichnung vorzuziehen sein. Ist die von mir vorgeschlagene praktisch verwendbar, so wird sie sich wohl einbürgern, sonst möge sie bald der Vergessenheit anheimfallen.

Wallace. A. R. — 1855.

On the law which has regulated the introduction of new species.

Annals and Magazine of Natural History, 2nd Series. 16:184-196.

PDF typeset file: 90,845 bytes - 17 pages - no figures

Today Darwin's name is known to everyone, while Alfred Russel Wallace is familiar to only a few. Yet the concept of evolution by natural selection was independently developed by Wallace and Darwin, with Wallace publishing first. This paper, and the 1858 manuscript he sent directly to Darwin, show clearly that, prior to Darwin's publication, Wallace had a firm grasp on the concept of evolution.

Weinberg, Wilhelm — 1908.

Über Vererbungsgesetze beim Menschen

Weinberg, Wilhelm 1908. Über Vererbungsgesetze beim Menschen. Zeitschrift für Induktive Abstammungs- und Vererbungslehre. 1:440-460.

Weinberg, Wilhelm — 1908.

Über Vererbungsgesetze beim Menschen

Weinberg, Wilhelm 1908. Über Vererbungsgesetze beim Menschen. Zeitschrift für Induktive Abstammungs- und Vererbungslehre. 1:377-392.

Wilhelm Weinberg is the Weinberg of Hardy-Weinberg fame. Although Hardy’s contribution to population genetics was just a single-page letter to the editor of Science, Weinberg produced a more thorough treatment of the effects on allele frequencies of Mendelian mechanisms acting alone. We know that Weinberg was familiar with Hardy’s letter, since he (Weinberg) wrote a brief summary of Hardy’s paper for the Resultate (abstracts) section of this issue of this journal (p. 395). In that summary, Weinberg wrote:

Hardy, G. H. Mendelian Proportions in a mixed Population. Science N. S., 28 1908 S. 49. Yule hatte die Ansicht ausgesprochen, dass Brachydaktylie als dominierender Charakter mit der Zeit 3/4 der Bevoelkerung ausmachen muesse. (Die Anschauung von einer Zunahme der dominierenden Charaktere hat uebrigens auch Plate [Ludwig Plate of the Berlin Landwirthschaftliche Hochschul] vertreten.) Hardy weist nun darauf hin, dass Panmixie bei alternativer Vererbung zu stabiler Bevoelkerung fuehren muesse, was fuer einen speziellen Fall bereits 1904 Pearson und zu Anfang 1908 unabhaeng von ihm und in einfacherer Weise Referent nachgewiesen hat. Siehe auch diese Zeitschrift S. 377 ff.

S. 377 ff. Roughly translated as: Yule had argued that, over time, brachydactyly should come to dominate 3/4 of the population. (The idea of an increase in the dominating characters was also made by Plate.) Hardy now points out that panmixie (random mating) in alternative inheritance must lead to a stable population, which Pearson had also proven in 1904 for a special case and again, in 1908 (independently of Hardy), in an easier way. See also this magazine p. 377 ff.

Weinberg, Wilhelm — 1908.

Über Vererbungsgesetze beim Menschen.

Zeitschrift für Induktive Abstammungs- und Vererbungslehre, 1:377-392.

PDF image facsimile file

An early contribution from Weinberg on the study of inheritance in humans.

Weinstein, Alexander — 1936.

The Theory of Multiple-strand Crossing Over

Genetics, 21: 490.

PDF image facsimile file

Weinstein, Alexander — 1936.

The Theory of Multiple-strand Crossing Over

Genetics, 21: 155-199.

PDF image facsimile file

Weinstein, Alexander — 1918.

Coincidence of Crossing Over in drosophila Melanogaster (ampelophila)

Genetics, 3: 135-172.

PDF image facsimile file

Weismann, August — 1889.

Essays Upon Heredity.

Oxford at the Clarendon Press

This is a full-text PDF image facsimile version of the entire 700-plus pages of the original volumes.

August Weismann was one of the most influential biologists of the late nineteenth century. In Essays Upon Heredity he presents a series of essays giving his thoughts on the mechanisms of heredity. Two of the essays offer specific refutation of the idea that acquired characters can be inherited.

Weismann, August — 1893.

The Germ-Plasm.

New York: Charles Scribner's Sons

This is a full-text PDF image facsimile version of the entire 477-page original book.

August Weismann was one of the most influential biologists of the late nineteenth century. In The Germ-Plasm he lays out a new theory of heredity, one based on the continuity of the germ-plasm (the gametes and the cells that give rise to the gametes) as opposed to the finite existence of the soma (the cells of the body).

Weismann introduces his book modestly:

Any attempt at the present time to work out a theory of heredity in detail may appear to many premature, and almost presumptuous: I confess there have been times when it has seemed so even to myself. I could not, however, resist the temptation to endeavour to penetrate the mystery of this most marvellous and complex chapter of life as far as my own ability and the present state of our knowledge permitted.

A key point in his theory is that it makes impossible the inheritance of acquired characteristics, and thus deals a death blow to Lamarckism, as well as to Darwin's pangenesis:

What first struck me when I began seriously to consider the problem of heredity, some ten years ago, was the necessity for assuming the existence of a special organised and living hereditary substance, which in all multicellular organisms, unlike the substance composing the perishable body of the individual, is transmitted from generation to generation. This is the theory of the continuity of the germ-plasm. My conclusions led me to doubt the usually accepted view of the transmission of variations acquired by the body (soma); and further research, combined with experiments, tended more and more to strengthen my conviction that in point of fact no such transmission occurs.

Weldon, W. F. R. — 1902.

Mendel's laws of alternative inheritance in peas.

Biometrika, 1:228-254.

PDF typeset file: 1,430,843 bytes - 33 pages - several figures

Textbook treatments of genetics often give the impression that upon being rediscovered Mendel's dominated the field. This is not so. Galton and his followers had been working for decades studying patterns of inheritance and had developed a formal quantitative model for the inheritance of "natural" (i.e., continuous) traits.

The biometricians, as they were called, felt that Mendel's work was a special case, valid only when applied to discontinuous traits in domesticated species. Weldon was a leading proponent of the biometrician school. This paper provides a strong summary of why the biometricians believed Mendel's work to be fundamentally flawed and of no general consequence. The paper concludes:

The fundamental mistake which vitiates all work based upon Mendel's method is the neglect of ancestry, and the attempt to regard the whole effect upon offspring, produced by a particular parent, as due to the existence in the parent of particular structural characters; while the contradictory results obtained by those who have observed the offspring of parents apparently identical in certain characters show clearly enough that not only the parents themselves, but their race, that is their ancestry, must be taken into account before the result of pairing them can be predicted.

Wilson, Edmund B. — 1900.

The Cell in Development and Inheritance, 2nd Edition

New York: The Macmillan Company

This is a full-text PDF image facsimile version of the entire 490-page original book.

Edmund B. Wilson was the leading cytologist of his time and The Cell in Development and Inheritance was the definitive text on cytology from 1896 into the 1930's. A modern reader will be surprised to see how many of the illustrations in the book seem familiar – versions of many of them still appear in textbooks of introductory biology.

The last chapter in the book is entitled "Theories of Inheritance and Development:, and it begins:

Every discussion of inheritance and development must take as its point of departure the fact that the germ is a single cell similar in its essential nature to any one of the tissue-cells of which the body is composed. That a cell can carry with it the sum total of the heritage of the species, that it can in the course of a few days or weeks give rise to a mollusk or a man, is the greatest marvel of biological science. In attempting to analyze the problems that it involves, we must from the outset hold fast to the fact, on which Huxley insisted, that the wonderful formative energy of the germ is not impressed upon it from without, but is inherent in the egg as a heritage from the parental life of which it was originally a part. The development of the embryo is nothing new. It involves no breach of continuity, and is but a continuation of the vital processes going on in the parental body. What gives development its marvelous character is the rapidity with which it proceeds and the diversity of the results attained in a span so brief.

But when we have grasped this cardinal fact, we have but focussed our instruments for a study of the real problem. How do the adult characteristics lie latent in the germ-cell; and how do they become patent as development proceeds? This is the final question that looms in the background of every investigation of the cell. In approaching it we may well make a frank confession of ignorance; for in spite of all that the microscope has revealed, we have not yet penetrated the mystery, and inheritance and development still remain in their fundamental aspects as great a riddle as they were to the Greeks. What we have gained is a tolerably precise acquaintance with the external aspects of development. The gross errors of the early preformationists have been dispelled.' We know that the germ-cell contains no predelineated embryo; that development is manifested, on the one hand, by the cleavage of the egg, on the other hand, by a process of differentiation, through which the products of cleavage gradually assume diverse forms and functions, and so accomplish a physiological division of labour. We can clearly recognize the fact that these processes fall in the same category as those that take place in the tissue-cells; for the cleavage of the ovum is a form of mitotic cell-division, while, as many eminent naturalists have perceived, differentiation is nearly related to growth and has its root in the phenomena of nutrition and metabolism. The real problem of development is the orderly sequence and correlation of these phenomena toward a typical result. We cannot escape the conclusion that this is the outcome of the organization of the germ-cells; but the nature of that which, for lack of a better term, we call "organization," is and doubtless long will remain almost wholly in the dark.

Wilson, Edmund B. — 1902.

Mendel's principles of heredity and the maturation of the germ cells.

Science, NS 16: 991-993.

PDF typeset file: 40,134 bytes - 5 pages - no figures

In this short note, E. B. Wilson calls attention to the possible relationship between Mendelian patterns of inheritance and the assortment of chromosomes in meiosis.

Wilson, Edmund B. — 1905.

The chromosomes in relation to the determination of sex in insects.

Science, N.S. 22:500-502.

PDF typeset file: 43,282 bytes - 8 pages - no figures

In this short note, Wilson (a leading cell biologist of his time) offers his endorsement of the idea that there is a relationship between specific chromosomes and the determination of sex in insects:

Material procured during the past summer demonstrates with great clearness that the sexes of Hemiptera show constant and characteristic differences in the chromosome groups, which are of such a nature as to leave no doubt that a definite connection of some kind between the chromosomes and the determination of sex exists in these animals. These differences are of two types. In one of these, the cells of the female possess one more chromosome than those of the male; in the other, both sexes possess the same number of chromosomes, but one of the chromosomes in the male is much smaller than the corresponding one in the female (which is in agreement with the observations of Stevens on the beetle Tenebrio).

Wilson's contribution is the observation that the various cases all seem to fall cleanly into one of two types — those in which the male seems to be missing a chromosome, and those in which the male is carrying a pair of mis-matched chromosomes. Wilson's goes on to note that he does not believe that the 'accessory chromosomes' are actual sex determinants as conjectured by McClung, but rather that they probably act in a quantitative, not qualitative manner.

Wilson's endorsement of the idea that chromosome make-up is related to sex determination greatly facilitated the later general acceptance of the notion that individual chromosomes might be related to individual traits. Of course, sex is not a simple Mendelian trait, such as round or wrinkled peas, but nonetheless the evidence that some aspect of phenotype (sex) was related to some aspect of genotype was an important initial step in bringing genetics together with cytology.

Wilson, Edmund B. — 1909.

Recent researches on the determination and heredity of sex.

Science, NS 29:53-70.

PDF image facsimile file: 18 pages

Wilson, Edmund B. — 1909.

Secondary chromosome-couplings and the sexual relations in Abraxas.

Science, NS 29:704-706.

PDF image facsimile file: 3 pages

Woods, F. A. — 1908.

Recent Studies in Human Heredity

The American Naturalist 42: 685-693.

Wright, Sewall and Chase, Herman B. — 1936.

On the Genetics of the Spotted Pattern of the Guinea Pig

Genetics, 21: 758-787.

PDF image facsimile file

Wright, Sewall — 1918.

On the nature of size factors.

Genetics, 3:367-374.

PDF image facsimile file: 8 pages - 0 figures

Wright, Sewall — 1921.

Systems of mating. I. The biometric relations between parent and offspring.

Genetics, 6:111-123.

PDF image facsimile file: 13 pages - 2 figures

Wright, Sewall — 1921.

Systems of mating. II. The effects of inbreeding on the genetic composition of a population.

Genetics, 6:124-143.

PDF image facsimile file: 20 pages - 12 figures

Wright, Sewall — 1921.

Systems of mating. III. Assortative mating based on somatic resemblance.

Genetics, 6:144-161.

PDF image facsimile file: 18 pages - 7 figures

Wright, Sewall — 1921.

Systems of mating. IV. The effects of selection.

Genetics, 6:162-166.

PDF image facsimile file: 5 pages - 1 figure

Wright, Sewall — 1921.

Systems of mating. V. General considerations.

Genetics, 6:167-178.

PDF image facsimile file: 12 pages - 7 figures

Wright, Sewall — 1925.

The factors of the albino series of guinea-pigs and their effects on black and yellow pigmentation.

Genetics, 10:223-260.

PDF image facsimile file: 38 pages - 5 figures

Wright, Sewall — 1927.

The effects in combination of the major color-factors of the guinea pig

Genetics, 12: 530-569.

PDF image facsimile file

Wright, Sewall — 1928.

An eight-factor cross in the guinea pig

Genetics, 13: 508-531.

PDF image facsimile file

Wright, Sewall — 1931.

Evolution in Mendelian populations.

Genetics, 16:97-159.

PDF image facsimile file: 63 pages - 21 figures

Wright, Sewall — 1932.

General, Group and Special Size Factors

Genetics, 17: 603-619.

PDF image facsimile file

Wright, Sewall — 1934.

An Analysis of Variability in Number of Digits in an Inbred Strain of Guinea Pigs

Genetics, 19: 506-536.

PDF image facsimile file

Wright, Sewall — 1934.

On the Genetics of Subnormal Development of the Head (otocephaly) in the Guinea Pig

Genetics, 19: 471-505.

PDF image facsimile file

Wright, Sewall — 1934.

The Results of Crosses Between Inbred Strains of Guinea Pigs, Differing in Number of Digits

Genetics, 19: 537-551.

PDF image facsimile file

Wright, Sewall and Eaton, O. N. — 1926.

Mutational Mosaic Coat Patterns of the Guinea Pig

Genetics, 11: 333-351.

PDF image facsimile file

Wright, Sewall. — 1931.

Evolution in Mendelian populations.

Genetics, 16:97-159.

PDF image facsimile file: 3.037,667 bytes - 63 pages - several figures

Soon after the establishment of Mendelian genetics, several workers began to explore how Mendelian mechanisms would affect changes in gene frequencies in populations — that is, they began to explore the implications of Mendelism for evolution.

Sewall Wright became one of the leading theoreticians who studied Mendelism in the context of population genetics. This paper is a key presentation of his thinking on how Mendelism and evolution might interact.

Wright, Sewall. — 1932.

Complementary Factors for Eye Color in Drosophila.

The American Naturalist, LXVI:282-283.

PDF typeset file: 7,701 bytes - 2 pages - no figures

There are two distinct biochemical pathways producing pigments that color the eyes of Drosophila melanogaster — one yields a bright red pigment, the other brown. When both are present, the eyes are dark-red. When one is present and the other absent, flies have brown or bright red eyes. When both are missing, flies have white eyes.

In 1932, Sewall Wright reported the first case where a cross between red-eyed and brown-eyed flies yielded double-recessive progeny with white eyes. What makes this observation interesting is that the work occurred as part of a class exercise in an undergraduate teaching laboratory at the University of Chicago. Not many modern undergraduate lab exercises yield publishable results.

Yule, G. Udny — 1902.

Mendel's laws and their probably relations to intra-racial heredity.

The New Phytologist, 1:193-207,222-238.

PDF image facsimile file: 32 pages

 

Weinberg, Wilhelm — 1908.

Über Vererbungsgesetze beim Menschen

Weinberg, Wilhelm 1908. Über Vererbungsgesetze beim Menschen. Zeitschrift für Induktive Abstammungs- und Vererbungslehre. 1:440-460.

Spillman, W. J. — 1909.

A Case of Non-Mendelian Heredity

The American Naturalist 43: 437-448.

Morgan, L. V. — 1933.

A Closed X Chromosome in Drosophila Melanogaster

Genetics, 18: 250-283.

PDF image facsimile file

Painter, Theophilus S. — 1928.

A Comparison of the Chromosomes of the Rat and Mouse with Reference to the Question of Chromosome Homology in Mammals

Genetics, 13: 180-189.

PDF image facsimile file

Galton, Francis. — 1898.

A Diagram of Heredity.

Nature, 57:293.

PDF typeset file: 27,776 bytes - 5 pages - one figure

Some standard textbook descriptions of early genetics give the impression that, besides Mendel, no one attempted any genetic analysis in the entire nineteenth century. This is far from the truth, with Francis Galton offering a fine refutation. Starting just a few years after Mendel (and also working with peas), Galton carried out a series of well-received studies that resulted in his "Ancestral Law of Heredity," summarized diagrammatically in this brief communication. Galton's "Law" was so firmly established in some circles, that many adherents did not accept Mendelism until 1918, when R. A. Fisher showed that Galton's Law was in fact a natural consequence of Mendelian inheritance for polygenic traits.

Muller, H. J., Raffel, D., Gershenson, S. M. , and Prokofyeva-Belgovskaya, A. A. — 1937.

A Further Analysis of Loci in the So-called "inert Region" of the X Chromosome of Drosophila

Genetics, 22: 87-93.

PDF image facsimile file

Sturtevant, A. H. — 1928.

A Further Study of the So-call Mutation at the Bar Locus of Drosophila

Genetics, 13:401-409

PDF image facsimile file

Sturtevant, Alfred H. — 1965.

A History of Genetics.

First published in 1965, it was brought back into print in 2001 by Cold Spring Harbor Laboratory Press and the Electronic Scholarly Publishing project.

This is a full-text PDF typeset version of the entire 167-page original book.

Between 1910 and 1915, the modern chromosomal theory of heredity was established, largely through work done in the laboratory of Thomas H. Morgan at Columbia University. This book, by one of Morgan's students, presents the history of early genetics and captures the excitement as a new discipline was being born.

Sturtevant himself made major contributions to genetics, including the development of the world's first genetic map in 1913.

Drinkwater, H. — 1910.

A Lecture on Mendelism.

London: J. M. Dent & Sons.

This is an image facsimile version of the entire 48-page original first edition.

This short book was based on a lecture given by Drinkwater as one of a series known as "Science Lectures for the People." The book provides insights into the general perception (as opposed to scholarly view) of genetics very early after the field had begun.

The book also contains some nice portraits of Mendel, Bateson, and Punnett.

Haldane, J. B. S. — 1934.

A Mathematical Theory of Natural and Artificial Selection Part X. Some Theorems on Artificial Selection

Genetics, 19: 412-429.

PDF image facsimile file

Alberts, Hugo W. — 1926.

A Method For Calculating Linkage Values

Genetics, 11: 235-248.

PDF image facsimile file

Painter, Theophilus S. — 1934.

A New Method For the Study of Chromosome Aberrations and the Plotting of Chromosome Maps in Drosophila melanogaster.

Genetics, 19: 175-188.

PDF image facsimile file: 915,967 bytes - 14 pages - 2 figures

Now, almost any reference to the genetics of Drosophila includes some illustration of the giant salivary gland chromosomes found in these flies. Although Drosophila had been used effectively since 1910, it was this paper by Painter that first showed the tremendous potential of these chromosomes for cytogenetic research. New discovery often hinges on new methods and this paper is truly a break-through study in genetic methodology.

Brink, R. A. and Cooper, D. C. — 1935.

A Proof That Crossing Over Involves an Exchange of Segments Between Homologous Chromosomes

Genetics, 20: 22-35.

PDF image facsimile file

Castle, W. E. — 1925.

A Sex Difference in Linkage in Rats and Mice

Genetics, 10: 580-582.

PDF image facsimile file

Morgan, L. V. — 1939.

A Spontaneous Somatic Exchange Between Non-homologous Chromosomes in Drosophila Melanogaster

Genetics, 24: 747-752.

PDF image facsimile file

Cook, Robert. — 1937.

A chronology of genetics.

Yearbook of Agriculture, pp. 1457-1477.

PDF typeset file: 251,867 bytes - 28 pages - one figure

Robert Cook, as editor of The Journal of Heredity, was especially well positioned to appreciate how the new science of genetics developed after the rediscovery of Mendel in 1900 and the establishment of the chromosome theory of inheritance by T. H. Morgan and his students.

In this essay, Cook traces the history of genetics to four main roots - mathematics, plant breeding, animal breeding, and cytology.

Creighton, Harriet B., and McClintock, Barbara. — 1935.

A correlation of cytological and genetical crossing-over in Zea mays. A Corroboration.

PNAS, 21:148-150.

PDF image facsimile file: 3 pages - no figures

Although Creighton and McClintock's 1931 paper — A correlation of cytological and genetical crossing-over in Zea mays. — had provided data in support of the notion that cytological crossing-over occurs and that it is accompanied by genetical crossing-over, some had criticized the relatively few data points in the paper. In this 1935 paper, the authors acknowledge the criticism, then explain why they will, in this paper, be sharing some additional corroborative data with little additional commentary:

There has recently been some skepticism expressed (Brink and Cooper, 1935) as to the value of the studies on the correlation of cytological and genetical crossing-over in maize published by Creighton and McClintock (1931) because of the fewness of the data. Since the paper by Stern (1931) dealing with Drosophila and having much more extensive data appeared at practically the same time and yielded the same conclusions, the authors felt it unnecessary to add to the ever-increasing amount of published work merely to record more evidence of the same nature without supplying anything essentially new or advancing. Therefore, confirmatory data which have accumulated since the time the joint paper mentioned above was published have not been considered for a separate publication. However, we now feel forced to add more data merely to counteract any suspicion that the evidence previously presented constituted insufficient proof. This will be done in as brief a form as possible, since a discussion of the method has been given in the paper mentioned above.

For additional commentary on Creighton and McClintock's important work, see Edward Coe and Lee B. Kass (2005) Proof of physical exchange of genes on the chromosomes. Proceedings of the National Academy of Sciences, USA. 102:6641-6646.

Creighton, Harriet B., and McClintock, Barbara. — 1931.

A correlation of cytological and genetical crossing-over in Zea mays.

PNAS, 17:492-497.

PDF image facsimile file: 6 pages - several figures

When Alfred Sturtevant created the first genetic map, he hypothesized that genetic recombination resulted from the actual exchange of chromatid fragments. However, at the time there was no hard evidence that proved recombination is accomplished via such a mechanism. The same genetic results could be explained if only alleles are exchanged during recombination, leaving the bulk of the chromatid arm unaffected. Since the two hypotheses make equivalent predictions regarding the distribution of alleles, they cannot be distinguished using purely genetic methods.

Attempting to demonstrate that genetic recombination is accomplished via the physical exchange of chromatid arms poses a problem similar to that encountered by Thomas H. Morgan when he first hypothesized that genes might be carried on the X chromosome. Although Morgan's genetic hypothesis of X-linkage provided an explanation for the inheritance of the white-eye allele in Drosophila, the notion that genes are actually carried on the X chromosome was not proven until Calvin Bridges provided cytological evidence to confirm the genetic observations. Bridges established a one-to-one correspondence between the abnormal distribution of eye-color alleles and the abnormal distribution of X chromosomes. That is, he established a relationship between genetic markers (the eye color alleles and their associated inheritance patterns) and cytological markers (the presence of abnormal sets of sex chromosomes).

In this paper, Creighton and McClintock present work in which they use a combination of cytological and genetic markers to show that cytological crossing-over occurs and that it is accompanied by genetical crossing-over. In just a few pages the authors accomplish their goal of establishing the reality of cytological recombination and of showing that it is associated with genetic recombination. This paper is truly a classic.

If this paper is read in isolation, the authors' discussion of their results can, at times, be difficult to follow. When this paper was originally published, however, it was accompanied by another paper (by McClintock) that immediately preceded it in the journal and that was intended to serve as an introduction to this paper. In the preceding paper, McClintock provided the basic genetic and cytological information necessary to understand the experimental logic of this paper. The background paper is The order of the genes C, Sh, and Wx in Zea mays with reference to a cytologically known point in the chromosome. The two papers should be read together, with the first, descriptive paper serving as a critical and necessary introduction to the second, experimental work.

For additional commentary on Creighton and McClintock's important work, see Edward Coe and Lee B. Kass (2005) Proof of physical exchange of genes on the chromosomes. Proceedings of the National Academy of Sciences, USA. 102:6641-6646.

Creighton, Harriet B., and McClintock, Barbara. — 1931.

A correlation of cytological and genetical crossing-over in Zea mays.

PNAS, 17:492-497.

PDF typeset file: 140,176 bytes - 17 pages - several figures

When Alfred Sturtevant created the first genetic map, he hypothesized that genetic recombination resulted from the actual exchange of chromatid fragments. However, at the time there was no hard evidence that proved recombination is accomplished via such a mechanism. The same genetic results could be explained if only alleles are exchanged during recombination, leaving the bulk of the chromatid arm unaffected. Since the two hypotheses make equivalent predictions regarding the distribution of alleles, they cannot be distinguished using purely genetic methods.

Attempting to demonstrate that genetic recombination is accomplished via the physical exchange of chromatid arms poses a problem similar to that encountered by Thomas H. Morgan when he first hypothesized that genes might be carried on the X chromosome. Although Morgan's genetic hypothesis of X-linkage provided an explanation for the inheritance of the white-eye allele in Drosophila, the notion that genes are actually carried on the X chromosome was not proven until Calvin Bridges provided cytological evidence to confirm the genetic observations. Bridges established a one-to-one correspondence between the abnormal distribution of eye-color alleles and the abnormal distribution of X chromosomes. That is, he established a relationship between genetic markers (the eye color alleles and their associated inheritance patterns) and cytological markers (the presence of abnormal sets of sex chromosomes).

In this paper, Creighton and McClintock present work in which they use a combination of cytological and genetic markers to show that cytological crossing-over occurs and that it is accompanied by genetical crossing-over. In just a few pages the authors accomplish their goal of establishing the reality of cytological recombination and of showing that it is associated with genetic recombination. This paper is truly a classic.

If this paper is read in isolation, the authors' discussion of their results can, at times, be difficult to follow. When this paper was originally published, however, it was accompanied by another paper (by McClintock) that immediately preceded it in the journal and that was intended to serve as an introduction to this paper. In the preceding paper, McClintock provided the basic genetic and cytological information necessary to understand the experimental logic of this paper. The background paper is The order of the genes C, Sh, and Wx in Zea mays with reference to a cytologically known point in the chromosome. The two papers should be read together, with the first, descriptive paper serving as a critical and necessary introduction to the second, experimental work.

For additional commentary on Creighton and McClintock's important work, see Edward Coe and Lee B. Kass (2005) Proof of physical exchange of genes on the chromosomes. Proceedings of the National Academy of Sciences, USA. 102:6641-6646.

McClintock, Barbara — 1929.

A cytological and genetical study of triploid maize

Genetics, 14: 180-222.

PDF image facsimile file

Cannon, W. A. — 1902.

A cytological basis for the Mendelian laws.

Bulletin of the Torrey Botanical Club, 29:657-661.

PDF typeset file: 191,965 bytes - 6 pages

Muller, Hermann J., Raffel, D., Gershenson, S. M., and Prokofya-Belgovskaya, A. A. — 1937.

A further analysis of loci in the so-called "inert region" of the X chromosome of Drosophila.

Genetics, 22:87-93.

PDF image facsimile file: 7 pages

Sturtevant, Alfred H. — 1928.

A further study of the so-called mutation at the bar locus of Drosophila.

Genetics, 13:401-409.

PDF image facsimile file: 9 pages - no figures

Shull, George H. — 1923.

A permanent memorial to Galton and Mendel.

The Scientific Monthly, 16: 263-270.

PDF typeset file: 247,951 bytes - 54 pages - no figures

In December of 1922, the American Society of Naturalists held a special session to honor the centenaries of the birth of Gregor Mendel and of Francis Galton. This is one of the four papers presented at that session and later published in the The Scientific Monthly.

Little, C. C. — 1914.

A possible Mendelian explanation for a type of inheritance apparently non-Mendelian in nature

Science, 40:904-906.

PDF image facsimile file: 530,978 bytes - 3 pages

Montgomery, Thos. H., Jr. — 1910.

ARE PARTICULAR CHROMOSOMES SEX DETERMINANTS?

Biological Bulletin, 19:1-17.

PDF image facsimile file

Wright, Sewall — 1934.

An Analysis of Variability in Number of Digits in an Inbred Strain of Guinea Pigs

Genetics, 19: 506-536.

PDF image facsimile file

Malthus, T. — 1798.

An Essay on the Principle of Population.

PDF typeset file: 948,754 bytes - 134 pages - no figures

In 1798, Thomas Malthus anonymously published this Essay, outlining why the forces of population growth tend to create a "struggle for existence" (see page 14). This book had a significant influence on Darwin as he looked for mechanisms that might explain evolutionary change. The influence shows, with Chapter Three of Darwin's Origin of Species entitled "Struggle for Existence". Now, 200 years after its first publication, Malthus' work is still an interesting read.

Rhoades, Marcus M. — 1933.

An Experimental and Theoretical Study of Chromatid Crossing Over

Genetics, 18: 535-555.

PDF image facsimile file

Wright, Sewall — 1928.

An eight-factor cross in the guinea pig

Genetics, 13: 508-531.

PDF image facsimile file

Riddle, Oscar. — 1924.

Any Hereditary Character and the Kinds of Things We Need to Know About It.

The American Naturalist, LVIII:410-425.

PDF typeset file: 80,148 bytes - 13 pages - no figures

This does not qualify as a classic genetics paper and I suspect that it has never before been included in a collection of important papers. However, it is included here because it provides a glimpse into some general aspects of genetic thought in the mid 1920's.

The premise of this essay is essentially that, as of its writing, " studies on heredity and evolution offer what is mainly a two-sided attack on a many-sided problem." This argument was well taken, but the modern reader may have difficulty appreciating other concerns of the essay.

Bateson, William. — 1902.

Application for Support of an Experimental Investigation of Mendel's Principles of Heredity in Animals and Plants.

In Bateson, B. 1928. William Bateson, F.R.S.: His Essays & Addresses, together with a Short Account of his Life. Cambridge: Cambridge University Press.

PDF typeset file: 36,348 bytes - 6 pages - no figures

Although not considered to be one of the "official" rediscovers of Mendel's work, William Bateson was the first English-speaking scientist to recognize the importance of Mendel's work and he immediately set out to bring Mendel's work to the attention of the scientific community. Bateson coined the word "genetics" to name the new field and made many important contributions to its development.

This present document is a copy of a letter that Bateson wrote in 1902, seeking financial support from the Trustees of the Carnegie Institution for continued investigations into Mendelian mechanisms of inheritance.

The letter was almost certainly the world's first grant application in the new field of genetics. It was declined.

Patterson, J. T. and Muller, H. J. — 1930.

Are "progressive" mutations produced by X-rays?

Genetics, 15: 495-577.

PDF image facsimile file

Powers, J. H. — 1909.

Are Species Realities or Concepts Only?

The American Naturalist

Morgan, Thomas H. — 1909.

Are the Drone Eggs of the Honey-Bee Fertilized?

The American Naturalist 43: 316-317.

Muller, Hermann J. — 1927.

Artificial transmutation of the gene.

Science, 46:84-87.

PDF image facsimile file: 1,002,392 bytes - 4 pages

Morgan, Thomas H. — 1909.

Breeding Experiments with Rats

The American Naturalist 43: 182-185.

Cox, Charles F. — 1909.

Charles Darwin and the Mutation Theory

The American Naturalist 43: 65-91.

Painter, Theophilus S. and Stone, Wilson — 1935.

Chromosome Fusion and Speciation in Drosophilae

Genetics, 20: 327-341.

PDF image facsimile file

Morgan, Thomas H. — 1910.

Chromosomes and Heredity.

The American Naturalist, 44:449-496.

PDF typeset file: 222,436 bytes - 38 pages - one figure

Work in the laboratory of T. H. Morgan was critical in establishing that genes are real, physical entities and that they are arranged in a linear order on chromosomes. In this early, analytical paper, Morgan considers whether or not chromosomes might be carriers of the hereditary material and whether or not they might control sex determination.

Morgan's careful and logical approach is captured in his final comments on sex determination:

Science advances by carefully weighing all of the evidence at her command. When a decision is not warranted by the facts, experience teaches that it is wise to suspend judgment, until the evidence can be put to further test. This is the position we are in today concerning the interpretation of the mechanism that we have found by means of which sex is determined. I could, by ignoring the difficulties and by emphasizing the important discoveries that have been made, have implied that the problem of sex determination has been solved. I have tried rather to weigh the evidence, as it stands, in the spirit of the judge rather than in that of the advocate. One point at least I hope to have made evident, that we have discovered in the microscopic study of the germ cells a mechanism that is connected in some way with sex determination; and I have tried to show, also, that this mechanism accords precisely with that the experimental results seem to call for. The old view that sex is determined by external conditions is entirely disproven, and we have discovered an internal mechanism by means of which the equality of the sexes where equality exists is attained. We see how the results are automatically reached even if we can not entirely understand the details of the process. These discoveries mark a distinct advance in our study of this difficult problem.

Morgan, Thomas H. — 1911.

Chromosomes and associative inheritance.

Science, New Series, 34:636-638.

PDF image facsimile file: 613,691 bytes - 3 pages - 0 figures

Morgan, Thomas H. — 1910.

Chromosomes and heredity.

The American Naturalist, 44: 449-496.

PDF typeset file: 284,612 bytes - 38 pages - no figures

Between 1910 and 1915, work in Morgan's lab laid the foundation of the modern chromosomal theory of heredity. This paper represents Morgan's thinking early in this process.

The opening lines of his paper captures the issues that he then deemed important to a consideration of the mechanism of heredity:

We have come to look upon the problem of heredity as identical with the problem of development. The word heredity stands for those properties of the germ-cells that find their expression in the developing and developed organism. When we speak of the transmission of characters from parent to offspring, we are speaking metaphorically; for we now realize that it is not characters that are transmitted to the child from the body of the parent, but that the parent carries over the material common to both parent and offspring. This point of view is so generally accepted to-day that I hesitate to restate it. It will serve at least to show that in what I am about to say regarding heredity and the germ-cells I shall ignore entirely the possibility that characters first acquired by the body are transmitted to the germ. Were there sufficient evidence to establish this view, our problem would be affected in so far as that we should not only have to account for the way in which the fertilized egg produces the characters of the adult, but also for the way in which the characters of the adult modify the germ-cells. The modern literature of development and heredity is permeated through and through by two contending or contrasting views as to how the germ produces the characters of the individual. One school looks upon the egg and sperm as containing samples or particles of all the characters of the species, race, line, or even of the individual. This view I shall speak of as the particulate theory of development. The other school interprets the egg or sperm as a kind of material capable of progressing in definite ways as it passes through a series of stages that we call its development. I shall call this view the theory of physico-chemical reaction, or briefly the reaction theory.

Weinstein, Alexander — 1918.

Coincidence of Crossing Over in drosophila Melanogaster (ampelophila)

Genetics, 3: 135-172.

PDF image facsimile file

Wright, Sewall. — 1932.

Complementary Factors for Eye Color in Drosophila.

The American Naturalist, LXVI:282-283.

PDF typeset file: 7,701 bytes - 2 pages - no figures

There are two distinct biochemical pathways producing pigments that color the eyes of Drosophila melanogaster — one yields a bright red pigment, the other brown. When both are present, the eyes are dark-red. When one is present and the other absent, flies have brown or bright red eyes. When both are missing, flies have white eyes.

In 1932, Sewall Wright reported the first case where a cross between red-eyed and brown-eyed flies yielded double-recessive progeny with white eyes. What makes this observation interesting is that the work occurred as part of a class exercise in an undergraduate teaching laboratory at the University of Chicago. Not many modern undergraduate lab exercises yield publishable results.

Morgan, Thomas H. — 1912.

Complete linkage in the second chromosome of the male of Drosophila

Science, 36:933-934.

PDF image facsimile file: 325,825 bytes - 2 pages

Tschermak, Erik von — 1900.

Concerning artificial crossing in Pisum sativum

First published in English as: Tschermak, E. 1950. Concerning artificial crossing in Pisum sativum. Genetics, 35(5, pt 2): 42-47. Originally published as: Tschermak, E. 1900. Über Künstliche Kreuzung bei Pisum sativum. Berichte der Deutsche Botanischen Gesellschaft 18: 232-239, 1900.

PDF typeset file: 62,114 bytes - 10 pages - no figures

Tschermak, along with Carl Correns and Hugo de Vries, is considered to be one of the three co-discovers of Mendel's work in 1900. He had been working himself with garden peas when he rediscovered Mendel's prior contributions. In a postscript to his paper, he wrote:

Correns has just published experiments which also deal with artificial hybridization of different varieties of Pisum sativum and observations of the hybrids left to self-fertilization through several generations. They confirm, just as my own, Mendel's teachings. The simultaneous "discovery" of Mendel by Correns, de Vries, and myself appears to me especially gratifying. Even in the second year of experimentation, I too still believed that I had found something new.

Vries, Hugo de — 1900.

Concerning the law of segregation of hybrids.

First published in English as: De Vries, H.. 1950. Concerning the law of segregation of hybrids. Genetics, 35(5, pt 2): 30-32. Originally published as: De Vries, H. 1900. Sur la loi de disjonction des hybrides. Comptes Rendus de l'Academie des Sciences (Paris), 130: 845-847.

PDF typeset file: 35,435 bytes - 6 pages - no figures

Hugo de Vries, along with Carl Correns and Erik von Tschermak, is considered to be one of the three co-discovers of Mendel's work in 1900. De Vries was by far the most established scientist at the time, with an established research record dealing with "mutations" (variations) and speciation.

In this first of two papers that he published in 1900, de Vries does not even mention Mendel by name, even though he adopts Mendelian terminology such as dominant and recessive.

Morgan, Thomas H. — 1922.

Croonian Lecture: On the Mechanism of Heredity.

Proceedings of the Royal Society, B, 94:162-197.

PDF typeset file: 3,916,605 bytes - 42 pages - 35 figures

The Croonian Lecture is the Royal Society's premier lecture in the biological sciences. Dr Croone, one of the original members of the Society, left on his death in 1684 a scheme for two lectureships, one at the Royal Society and the other at the Royal College of Physicians

Morgan was invited to give the Croonian lecture in 1922 - a recognition of his pioneering work in elucidating the physical basis of heredity.

Belling, John — 1933.

Crossing Over and Gene Rearrangement in Flowering Plants

Genetics, 18: 388-413.

PDF image facsimile file

Goldschmidt, Richard — 1917.

Crossing Over ohne Chiasmatypie?

Genetics, 2:82-95.

PDF image facsimile file: 764,480 bytes - 14 pages - 2 figures

Sturtevant, A. H. — 1917.

Crossing Over without Chiasmatype?

Genetics, 2:301-304.

PDF image facsimile file: 220,991 bytes - 4 pages - no figures

Bridges, Calvin B., and Anderson, E. G. — 1925.

Crossing over in the X chromosomes of triploid females of Drosophila melanogaster..

Genetics, 10:418-441.

PDF image facsimile file: 24 pages

Payne, F. — 1924.

Crossover Modifiers in the Third Chromosome of Drosophila melanogaster

Genetics, 9: 327-342.

PDF image facsimile file

Sivertzev-Dobzhansky, N. P. and Dobzhansky, Th. — 1933.

Deficiency and Duplications For the Gene Bobbed in Drosophila Melanogaster

Genetics, 18: 413.

PDF image facsimile file

Bridges, Calvin B. — 1917.

Deficiency.

Genetics, 2:445-465.

PDF image facsimile file: 21 pages

Beadle, G. W. and Ephrussi, Boris — 1937.

Development of Eye Colors in Drosophila: Diffusible Substances and Their Interrelations

Genetics, 22: 76-86.

PDF image facsimile file

Ephrussi, Boris and Beadle, G. W. — 1937.

Development of Eye Colors in Drosophila: Production and Release of cn+ Substance by the Eyes of Different Eye Color Mutants

Genetics, 22: 479-483.

PDF image facsimile file

Harnly, Morris Henry and Ephrussi, Boris — 1937.

Development of Eye Colors in Drosophila: Time of Action of Body Fluid on Cinnabar

Genetics, 22: 393-401.

PDF image facsimile file

Ephrussi, Boris and Beadle, G. W. — 1937.

Development of Eye Colors in Drosophila: Transplantation Experiments on the Interaction of Vermilion with Other Eye Colors

Genetics, 22: 65-75.

PDF image facsimile file

Bridges, Calvin B. — 1914.

Direct proof through non-disjunction that the sex-linked genes of Drosophila are borne on the X-chromosome.

Science, NS vol. XL:107-109.

PDF typeset file: 24,076 bytes - 5 pages - no figures

Although Bridges' longer 1916 Genetics paper (vol 1, page 1) on the same topic is better known and treats the issue at much greater length, this short communication in Science contains the same argument and is equally persuasive.

By 1910, much evidence had been presented to demonstrate that sexual phenotype (i.e., maleness or femaleness) was determined by chromosomes. And, as early as 1902 Sutton noted that similarities in the behavior of genes and chromosomes suggested that Mendelian factors might be carried on chromosomes.

Here, Bridges shows that mis-assortment of the sex chromosomes is accompanied by atypical inheritance patterns for sex-linked traits and he argues that this proves that genes are carried on chromosomes. He concludes his paper: "there can be no doubt that the complete parallelism between the unique behavior of the chromosomes and the behavior of sex-linked genes and sex in this case means that the sex-linked genes are located in and borne by the X-chromosomes."

Dobzhansky, Th. — 1935.

Drosophila Miranda, a New Species

Genetics, 20: 377-391.

PDF image facsimile file

Weismann, August — 1889.

Essays Upon Heredity.

Oxford at the Clarendon Press

This is a full-text PDF image facsimile version of the entire 700-plus pages of the original volumes.

August Weismann was one of the most influential biologists of the late nineteenth century. In Essays Upon Heredity he presents a series of essays giving his thoughts on the mechanisms of heredity. Two of the essays offer specific refutation of the idea that acquired characters can be inherited.

Wright, Sewall — 1931.

Evolution in Mendelian populations.

Genetics, 16:97-159.

PDF image facsimile file: 63 pages - 21 figures

Wright, Sewall. — 1931.

Evolution in Mendelian populations.

Genetics, 16:97-159.

PDF image facsimile file: 3.037,667 bytes - 63 pages - several figures

Soon after the establishment of Mendelian genetics, several workers began to explore how Mendelian mechanisms would affect changes in gene frequencies in populations — that is, they began to explore the implications of Mendelism for evolution.

Sewall Wright became one of the leading theoreticians who studied Mendelism in the context of population genetics. This paper is a key presentation of his thinking on how Mendelism and evolution might interact.

Bateson, William, Saunders, E. R., and Punnett, R. C. — 1904.

Experimental Studies in the Physiology of Heredity.

Reports to the Evolution Committee of the Royal Society, II, 1904, pp. 1-131

PDF image facsimile file: 6,907,359 bytes - 154 pages - no figures

William Bateson was the first English-speaking scientist to appreciate the potential significance of Mendel's work. He and his co-workers began immediately to confirm and extend Mendel's findings. This report to the evolution committee of the Royal Society represents one of the very first systematic investigations into Mendelism as a possible general explanation for the fundamental mechanisms of heredity.

Mendel, Gregor. — 1865.

Experiments in plant hybridization. (annotated)

Verhandlungen des naturforschenden Vereines in Brünn, Bd. IV für das Jahr 1865, Abhandlungen, 3-47.

PDF typeset file: 395,699 bytes - 41 pages - no figures

In February and March of 1865, Gregor Mendel presented the Brünn Natural History Society in Brünn, Czechoslovakia, with the results of his investigations into the mechanisms governing inheritance in pea plants. The next year, the work was published as Mendel, Gregor. 1866. "Versuche über Pflanzen Hybriden." Verhandlungen des naturforschenden Vereines in Brünn, 4:3-47.

In this remarkable paper, Mendel laid the groundwork for later became the science of genetics. However, the work was largely ignored when it appeared and Mendel moved on to other things. He died in 1884.

His work was rediscovered at the turn of the century and its significance immediately recognized. Genetics, as a formal scientific discipline, exploded into activity in 1900.

A non-annotated version of Mendel's paper is also available.

For those wishing to see and read Mendel in the original, a facsimile reprint edition is available. This version is in Adobe PDF format, but the pages are images of the original publication, not a new type-setting of the material.

You may also wish to visit The Mendel Web site, created by Roger Blumberg. The site offers many additional resources for the Mendel scholar.

Mendel, Gregor. — 1865.

Experiments in plant hybridization. (facsimile of first edition)

Verhandlungen des naturforschenden Vereines in Brünn, Bd. IV für das Jahr 1865, Abhandlungen, 3-47.

PDF image facsimile file: 2,142,414 bytes - 47 pages - no figures

For those wishing to see and read Mendel in the original, this provides an image facsimile of the original paper as it was published in German.

Mendel, Gregor. — 1865.

Experiments in plant hybridization.

Verhandlungen des naturforschenden Vereines in Brünn, Bd. IV für das Jahr 1865, Abhandlungen, 3-47.

PDF typeset file: 395,699 bytes - 41 pages - no figures

In February and March of 1865, Gregor Mendel presented the Brünn Natural History Society in Brünn, Czechoslovakia, with the results of his investigations into the mechanisms governing inheritance in pea plants. The next year, the work was published as Mendel, Gregor. 1866. "Versuche über Pflanzen Hybriden." Verhandlungen des naturforschenden Vereines in Brünn, 4:3-47.

In this remarkable paper, Mendel laid the groundwork for later became the science of genetics. However, the work was largely ignored when it appeared and Mendel moved on to other things. He died in 1884.

His work was rediscovered at the turn of the century and its significance immediately recognized. Genetics, as a formal scientific discipline, exploded into activity in 1900.

An annotated version of Mendel's paper is also available. The annotated version contains explanatory notes throughout the document. This can be useful to those reading Mendel's paper for the first time.

For those wishing to see and read Mendel in the original, a facsimile reprint edition is available. This version is in Adobe PDF format, but the pages are images of the original publication, not a new type-setting of the material.

You may also wish to visit The Mendel Web site, created by Roger Blumberg. The site offers many additional resources for the Mendel scholar.

Hurst, C. C. — 1904.

Experiments with Poultry.

Reports to the Evolution Committee of the Royal Society, II, 1904, pp. 131-154

PDF image facsimile file: 6,907,359 bytes - 154 pages - no figures

William Bateson was the first English-speaking scientist to appreciate the potential significance of Mendel's work. He and his co-workers began immediately to confirm and extend Mendel's findings. C. C. Hurst was one of Wm Bateson's early co-workers. This report to the evolution committee of the Royal Society represents one of the very first systematic investigations into Mendelism as a possible general explanation for the fundamental mechanisms of heredity.

Morgan, Thomas H. — 1913.

Factors and Unit Characters in Mendelian Heredity.

The American Naturalist, 47:5-16.

PDF image facsimile file: 741,353 bytes - 14 pages - 0 figures

Müller, F. — 1869.

Facts and Arguments for Darwin.

London: John Murray, Albemarle Street

Johann Friedrich Theodor Müller (March 31, 1821 – May 21, 1897), always known as Fritz, was a German biologist and physician who emigrated to southern Brazil, where he lived in and near the German community of Blumenau, Santa Catarina. There he studied the natural history of the Atlantic forest south of São Paulo, and was an early advocate of Darwinism. He lived in Brazil for the rest of his life. Müllerian mimicry is named after him.

Müller became a strong supporter of Darwin. He wrote Für Darwin in 1864, arguing that Charles Darwin's theory of evolution by natural selection was correct, and that Brazilian crustaceans and their larvae could be affected by adaptations at any growth stage. This was translated into English by W.S. Dallas as Facts and Arguments for Darwin in 1869 (Darwin sponsored the translation and publication). If Müller had a weakness it was that his writing was much less readable than that of Darwin or Wallace; both the German and English editions are hard reading indeed, which has limited the appreciation of this significant book.

Demerec, M. — 1937.

Frequency of Spontaneous Mutations in Certain Stocks of Drosophila melanogaster

Genetics, 22: 469-478.

PDF image facsimile file

Dobzhansky, Th. — 1937.

Further Data on the Variation of the Y Chromosome in Drosophila Pseudoobscura

Genetics, 22: 340-346.

PDF image facsimile file

Beadle, G. W. and Emerson, Sterling — 1935.

Further Studies of Crossing Over in Attached-x Chromosomes of Drosophila Melanogaster

Genetics, 20: 192-206.

PDF image facsimile file

Correns, Carl — 1900.

G. Mendel's law concerning the behavior of progeny of varietal hybrids.

First published in English as: Correns, C., 1950. G. Mendel's law concerning the behavior of progeny of varietal hybrids. Genetics, 35(5, pt 2): 33-41. Originally published as: Correns, C. 1900. G. Mendels Regel über das Verhalten der Nachkommenschaft der Rassenbastarde. Berichte der Deutschen Botanischen Gesellschaft, 18: 158-168.

PDF typeset file: 78,900 bytes - 14 pages - no figures

Correns, along with Hugo de Vries and Erik von Tschermak, is considered to be one of the three co-discovers of Mendel's work in 1900. Correns was the only one of the three to acknowledge Mendel in the title of his paper. Correns' paper begins:

The latest publication of Hugo de Vries: Sur la loi de disjonction des hybrides, which through the courtesy of the author reached me yesterday, prompts me to make the following statement: In my hybridization experiments with varieties of maize and peas, I have come to the same results as de Vries, who experimented with varieties of many different kinds of plants, among them two varieties of maize. When I discovered the regularity of the phenomena, and the explanation thereof - to which I shall return presently - the same thing happened to me which now seems to be happening to de Vries: I thought that I had found something new. But then I convinced myself that the Abbot Gregor Mendel in Brünn, had, during the sixties, not only obtained the same result through extensive experiments with peas, which lasted for many years, as did de Vries and I, but had also given exactly the same explanation, as far as that was possible in 1866.

Harris, J. Arthur — 1923.

Galton and Mendel: Their contribution to genetics and their influence on biology.

The Scientific Monthly, 16: 247-263.

PDF typeset file: 247,951 bytes - 54 pages - no figures

In December of 1922, the American Society of Naturalists held a special session to honor the centenaries of the birth of Gregor Mendel and of Francis Galton. This is one of the four papers presented at that session and later published in the The Scientific Monthly.

Wright, Sewall — 1932.

General, Group and Special Size Factors

Genetics, 17: 603-619.

PDF image facsimile file

Shull, G. H. — 1915.

Genetic Definitions in the New Standard Dictionary.

The American Naturalist, 49:52-59.

PDF typeset file: 78,002 bytes - 12 pages - no figures

In this short paper, Shull takes exception to some recently published dictionary definitions of many technical genetics terms and he offers corrected definitions in their stead. The main value of this paper to modern readers is that it gives a very good idea of what geneticists (or at least this geneticist) meant by their use of genetic terminology at the time. Although many of Shull's proffered definitions would be at home in a modern biology text, some are no longer in current usage.

Shull could have done a better job of defining "alternative inheritance" by adding "contrast with continuous inheritance," since at the time of his writing there was still a school of thought that argued that most heritable variation was continuous but that Mendelian theories provided explanations only for cases of "alternative inheritance," which were rare in nature and might only represent artifacts of inheritance in domesticated organisms.

For just such a criticism of alternative inheritance, see Weldon, W. F. R. 1902 Mendel's laws of alternative inheritance in peas. Biometrika, 1:228-254.

Tan, C. C. — 1936.

Genetic Maps of the Autosomes in Drosophila Pseudoobscura

Genetics, 21: 796-807.

PDF image facsimile file

Muller, Hermann J. — 1918.

Genetic Variability, Twin Hybrids and Constant Hybrids, in a Case of Balanced Lethal Factors

Genetics, 3: 422-499.

PDF image facsimile file

Sturtevant, Alfred H. — 1920.

Genetic studies on Drosophila simulans. I. Introduction. Hybrids with Drosophila melanogaster.

Genetics, 5:488-500.

PDF image facsimile file: 13 pages - 5 figures

Sturtevant, Alfred H. — 1921.

Genetic studies on Drosophila simulans. II. Sex-linked groups of genes.

Genetics, 6:43-64.

PDF image facsimile file: 22 pages - 5 figures

Sturtevant, Alfred H. — 1921.

Genetic studies on Drosophila simulans. III. Autosomal genes. General discussion.

Genetics, 6:179-207.

PDF image facsimile file: 29 pages - 6 figures

Muller, Hermann J. — 1918.

Genetic variability, twin hybrids and constant hybrids, in a case of balanced lethal factors.

Genetics, 3:422-499.

PDF image facsimile file: 78 pages

Bridges, Calvin B., Skoog, Eleanor Nichols, and Li, Ju-chi. — 1936.

Genetical and cytological studies of a deficiency (notopleural) in the second chromosome of Drosophila melanogaster.

Genetics, 21:788-795.

PDF image facsimile file: 8 pages

Sturtevant, A. H. and Dobzhansky, Th. — 1936.

Geographical Distribution and Cytology of "sex Ratio" in Drosophila Pseudoobscura and Related Species

Genetics, 21: 473-490.

PDF image facsimile file

Mendel, Gregor — 1866-1873.

Gregor Mendel's letters to Carl Nägeli, 1866-1873.

First published in English as: Mendel, G. 1950. Gregor Mendel's Letters to Carl Nägeli. Genetics, 35(5, pt 2): 1-29. Originally published as: Abhandlungen der Mathematisch-Physischen Klasse der Königlich Sächsischen Gesellschaft der Wissenschaften 29: 189-265, 1905. Reprinted in "Carl Correns, Gesammelte Abhandlungen zur Vererbungswissenschaft aus periodischen Schriften" 1899-1924. (Fritz V. Wettstein ed.) Berlin, Julius Springer, 1924. pp. 1237-1281.

PDF typeset file: 206,438 bytes - 36 pages - no figures

After his original paper on peas, Mendel published only one other paper on genetics, that one on Hieracium. These letters to Nägeli provide a rare additional glimpse into Mendel's thinking as he pursued his investigations on heredity.

Castle, W. E. — 1911.

Heredity in Relation to Evolution and Animal Breeding.

New York: D. Appleton and Company

This is an image facsimile version of the entire 184-page original edition.

Doncaster, L. — 1911.

Heredity in the Light of Recent Research.

Cambridge: University Press

This is an image facsimile version of the entire 144-page original first edition.

Davenport, Gertrude C, and Davenport, Charles B. — 1909.

Heredity of Hair Color in Man

The American Naturalist 43: 193-211.

Thomson, J. Arthur. — 1908.

Heredity.

London: John Murray

This is a PDF image facsimile version of the entire 596-page original first edition.

This book is one of the first textbook treatments of heredity after the rediscovery of Mendel's work. Thomson provides his analysis in the context of the understanding of inheritance in the pre-Mendelian late nineteenth century. Chapter 11, History of Theories of Heredity and Inheritance summarizes many of the nineteenth-century theories of heredity.

In his bibliography, Thomson cites many nineteenth-century works. He also provides a subject-index to the bibliography, making this collection of citations especially valuable.

East, E. M. — 1936.

Heterosis

Genetics, 21: 375-397.

PDF image facsimile file

Bateson, William. — 1899.

Hybridisation and cross-breeding as a method of scientific investigation.

Journal of the Royal Horticultural Society, 24:59-66.

PDF typeset file: 89,523 bytes - 13 pages - no figures

In this talk, given in 1899, before Mendel's work had been rediscovered, Bateson gives his vision of what kind of research will be necessary to shed light on the processes of inheritance and evolution:

What we first require is to know what happens when a variety is crossed with its nearest allies. If the result is to have a scientific value, it is almost absolutely necessary that the offspring of such crossing should then be examined statistically. It must be recorded how many of the offspring resembled each parent and how many shewed characters intermediate between those of the parents. If the parents differ in several characters, the offspring must be examined statistically, and marshalled, as it is called, in respect of each of those characters separately.

One would be hard pressed to provide a better anticipation of the experimental approach of Gregor Mendel. Small wonder that Bateson, upon encountering Mendel's work, quickly became convinced that the correct method for studying inheritance was finally at hand.

Morgan, Thomas H. — 1909.

Hybridology and Gynandromorphism

The American Naturalist

Garrod, Archibald. — 1923.

Inborn Errors of Metabolism, Second Edition.

London: Henry Frowde and Hodder & Stoughton

This is a full-text PDF image facsimile version of the entire 216-page original book.

Less than two years after the rediscovery of Mendelism and just a few years after the word biochemistry was first coined, Garrod reported on alkaptonuria in humans and came to the conclusion that it was inherited as a Mendelian recessive and that the occurrence of mutations (sports in the word of the time) in metabolic function should be no more surprising than inherited variations in morphology.

In 1908, he summarized his thinking about "inborn errors of metabolism" (his term for what we would now think of as mutations in genes affecting metabolic function) in a book. An image facsimile of the second edition (1923) of that book is presented here.

Like Mendel's work, Garrod's insights were so far ahead of their time that his entire work on metabolic mutations was largely neglected, until later efforts to elucidate the physiological functioning of genes led to the Nobel-prize-winning one-gene, one-enzyme hypothesis.

Haldane, J. B. S. and Waddington, C. H. — 1931.

Inbreeding and Linkage

Genetics, 16: 357-374.

PDF image facsimile file

Dunn, L. C. — 1920.

Independent Genes in Mice

Genetics, 5: 344-361.

PDF image facsimile file

Plough, Harold H. and Ives, Philip T. — 1935.

Induction of Mutations by High Temperature in Drosophila

Genetics, 20: 42-69.

PDF image facsimile file

Davenport, Charles B. — 1917.

Inheritance of Stature

Genetics, 2: 313-389.

PDF image facsimile file

Demerec, M. — 1923.

Inheritance of White Seedlings in Maize

Genetics, 8: 561-593.

PDF image facsimile file

Sturtevant, Alfred H. — 1923.

Inheritance of the direction of coiling in Limnaea.

Science, 58:269-270.

PDF typeset file: 150,314 bytes - 7 pages - no figures

As evidence mounted for the chromosomal basis of inheritance, occasional examples were discovered that seemed to challenge the Mendelian model, as mapped to the chromosomes by T. H, Morgan and his students. In this paper, A. H. Sturtevant (one of Morgan's students) shows that apparently aberrant patterns of inheritance can be seen to correspond to the Mendelian model, if care is taken to assign phenotype to the correct individual.

The case in question is the direction of shell coiling in snails of the genus Limnaea. These shells can either coil to the right (dextral) or left (sinistral). Coiling seemed to be an inherited trait, except that the observed patterns of inheritance were strange. Broods of offspring from sinistral snails, produced by self-fertilization (these snails are hermaphroditic) were either all sinistral or all dextral (never some of each). The same was found true if the single parent was dextral. Complicated models had been offered to explain these results, but here Sturtevant shows that a much simpler model is equally effective:

An analysis of the data presented suggests that the case is a simple Mendelian one, with the dextral character dominant, but with the nature of a given individual determined, not by its own constitution but by that of the unreduced egg from which it arose.

A similar problem exists with the color of bird eggs. Chickens, for example, can produce eggs that are either brown or white, and these colors are genetically determined. However, the trait "shell color" is an attribute of the hen laying the eggs, not of the chick that hatches out of the egg. When you realize that the shell is created as a secretion in the hen's oviducts, this makes perfect sense, even though the actual egg shell is ultimately separate from the body of the hen and is part of the egg from which the chick hatches.

The direction of shell coiling is now known to be controlled by specific proteins present in the cytoplasm of the egg. These proteins are produced early in egg development, prior to fertilization, and so are produced solely from genes present in the mother. Just as with the color of egg shells in chickens, the direction of shell coiling in Limnaea is really part of the phenotype of the mother of the snail, not of the snail actually wearing the shell.

Vries, Hugo de. — 1910.

Intracellular Pangenesis.

Chicago: The Open Court Publishing Co.

This is a full-text PDF image facsimile version of the entire 270-page original book

This classic work, first published in German in 1889, presents De Vries's theory of the pangen, a morphological structure carrying hereditary material. The name "gene," later coined by Johannsen, was derived from de Vries's pangen.

Hugo De Vries is often now remembered, along with Correns and von Tschermak, primarily for their role in the rediscovery of Mendel in 1900. Of the three, however, De Vries was by far the most established scientist. He was one of the most well-known botanists in Europe and had already been developing his own theoretical model of heredity - intracellular pangenesis.

Intracellular pangenesis was based on Darwins's concept of pangenesis as presented in chapter 27 of his massive, two-volume The Variation of Animals and Plants under Domestication. De Vries view, however, has a more modern feel than Darwin's, as De Vries thought about the inheritance of individual characters (as did Mendel), not just about more general overall species characteristics. De Vries called his units of inheritance pangens and later he came to believe that a pangen for a particular trait was the same, no matter in which species it occurred. This is an interesting anticipation of what would later be seen as genetic homology.

Dobzhansky, Th. and Sturtevant, A. H. — 1938.

Inversions in the Chromosomes of Drosophila Pseudoobscura

Genetics, 23: 28-64.

PDF image facsimile file

Castle, W.E. — 1919.

Is the arrangement of the genes in the chromosome linear?

Proceedings of the National Academy of Sciences, 5:25-32.

PDF image facsimile file: 615,957 bytes - 8 pages

Dunn, L. C. — 1920.

Linkage in Mice and Rats

Genetics, 5: 325-343.

PDF image facsimile file

Bateson, William. — 1894.

Materials for the Study of Variation.

London: Macmillan and Company.

This is a full-text PDF image facsimile version of the entire 598-page original first edition.

William Bateson was the first English-speaking scientist to recognize the significance of Mendel's work. Before the rediscovery of Mendel's work in 1900, Bateson had been active in studying morphology, with a special interest in discontinuous variation as it might apply to the origin of species.

In this book Bateson summarizes his observations on discontinuous variation. His concern for this kind of variation probably contributed greatly to the quickness with which he grasped the significance of Mendel's work.

NOTE: This is an electronic FACSIMILE of the original work. The PDF files contain images of the original pages. The files are large and will download slowly. It is probably best to download the files to disk for later viewing and printing. When printed, these files give output equivalent to good quality Xerox copies of the original.

East, E. M. — 1923.

Mendel and his contemporaries.

The Scientific Monthly, 16: 225-237.

PDF typeset file: 247,951 bytes - 54 pages - no figures

In December of 1922, the American Society of Naturalists held a special session to honor the centenaries of the birth of Gregor Mendel and of Francis Galton. This is one of the four papers presented at that session and later published in the The Scientific Monthly.

Bateson, William. — 1902.

Mendel's Principles of Heredity: A Defence.

London: Cambridge University Press.

This is a full-text PDF image facsimile version of the entire 212-page original first edition.

William Bateson was the first English-speaking scientist to recognize the significance of Mendel's work. In an 1899 paper, he had anticipated the sort of experimental design that Mendel used, and in 1900, shortly after Mendel's rediscovery, he published another paper in which he summarized Mendel's work in English, declaring it to be "a new principle of the highest importance."

In the present work, Bateson offers a book-length presentation of Mendel's approach to genetic research, including the first English translation of both Mendel's work on peas and his later work on Hieracium. The book is subtitled A Defence because the Mendelian approach to genetics was initially strongly resisted by the biometrician school, which based their thinking on Galton's ancestral law of heredity.

NOTE: This is an electronic FACSIMILE of the original work. The PDF files contain images of the original pages. The files are large and will download slowly. It is probably best to download the files to disk for later viewing and printing. When printed, these files give output equivalent to good quality Xerox copies of the original.

Yule, G. Udny — 1902.

Mendel's laws and their probably relations to intra-racial heredity.

The New Phytologist, 1:193-207,222-238.

PDF image facsimile file: 32 pages

Weldon, W. F. R. — 1902.

Mendel's laws of alternative inheritance in peas.

Biometrika, 1:228-254.

PDF typeset file: 1,430,843 bytes - 33 pages - several figures

Textbook treatments of genetics often give the impression that upon being rediscovered Mendel's dominated the field. This is not so. Galton and his followers had been working for decades studying patterns of inheritance and had developed a formal quantitative model for the inheritance of "natural" (i.e., continuous) traits.

The biometricians, as they were called, felt that Mendel's work was a special case, valid only when applied to discontinuous traits in domesticated species. Weldon was a leading proponent of the biometrician school. This paper provides a strong summary of why the biometricians believed Mendel's work to be fundamentally flawed and of no general consequence. The paper concludes:

The fundamental mistake which vitiates all work based upon Mendel's method is the neglect of ancestry, and the attempt to regard the whole effect upon offspring, produced by a particular parent, as due to the existence in the parent of particular structural characters; while the contradictory results obtained by those who have observed the offspring of parents apparently identical in certain characters show clearly enough that not only the parents themselves, but their race, that is their ancestry, must be taken into account before the result of pairing them can be predicted.

Wilson, Edmund B. — 1902.

Mendel's principles of heredity and the maturation of the germ cells.

Science, NS 16: 991-993.

PDF typeset file: 40,134 bytes - 5 pages - no figures

In this short note, E. B. Wilson calls attention to the possible relationship between Mendelian patterns of inheritance and the assortment of chromosomes in meiosis.

Hardy, G. H. — 1908.

Mendelian Proportions in a Mixed Population.

Science, NS. XXVIII:49-50.

PDF typeset file: 19,473 bytes - 1 page - no figures

Every geneticist has heard of the Hardy-Weinberg Law and of Hardy-Weinberg Equilibrium, and nearly all basic biology texts teach that G. H. Hardy played a seminal role in founding population genetics. But, what most biologists don't realize is that Hardy's total contribution to biology consisted of a single letter to the editor in Science. The letter began,

I am reluctant to intrude in a discussion concerning matters of which I have no expert knowledge, and I should have expected the very simple point which I wish to make to have been familiar to biologists. However, some remarks of Mr. Udny Yule, to which Mr. R. C. Punnett has called my attention, suggest that it may still be worth making.

With that, Hardy offered his "simple point" and then washed his hands of biology. His autobiography, A Mathematician's Apology, makes no mention of population genetics.

Punnett, R. C. — 1905.

Mendelism, 1st Edition.

Cambridge: Bowes and Bowes

PDF image facsimile file: 1,382,040 bytes - 71 pages - several figures

This little book is the first edition of the first genetics textbook ever written. It was published just five years after Mendel's work was rediscovered.

Punnett, R. C. — 1907.

Mendelism, 2nd Edition.

Cambridge: Bowes and Bowes

PDF image facsimile file: 1,832,735 bytes - 93 pages - several figures

This second edition of Punnett's text on Mendelism came out just two years after the first edition. In this new edition, Punnett Squares appeared for the first time. Also, the author included an index (that could fit on a single page with room left over).

Vries, Hugo De — 1925.

Mutant Races Derived from Oenothera Lamarckiana Semigigas

Genetics, 10: 211-222.

PDF image facsimile file

Vries, Hugo de — 1925.

Mutant races derived from Oenothera lamarckiana semigigas.

Genetics, 10:211-222.

PDF image facsimile file: 12 pages

Wright, Sewall and Eaton, O. N. — 1926.

Mutational Mosaic Coat Patterns of the Guinea Pig

Genetics, 11: 333-351.

PDF image facsimile file

Vries, Hugo de — 1918.

Mutations of Oenothera suaveolens desf.

Genetics, 3:1-26.

PDF image facsimile file: 26 pages

Luria, S. E., and Delbrück, M. — 1943.

Mutations of bacteria from virus sensitivity to virus resistance.

Genetics, 28:491-511

PDF typeset file: 201,354 bytes - 37 pages - several figures

This classic paper is the "fluctuation test" in which Luria and Delbrü first demonstrated the occurrence of microbial genetics. In fact, the fluctuation test must be regarded as the founding of bacterial genetics since it gave the first real proof that bacteria both possessed genes and experienced mutation. Luria and Delbrück shared the 1969 Nobel Prize with Alfred Hershey.

Luria and Delbrück were also able to use their data to calculate the actual mutation rate per bacterial cell division. Averaged across all of their experiments, this came to approximately 2.45 x 10-8. Thus, they not only proved that true genetic mutations occurred in bacteria, but also that such mutations were just as rare in bacteria as they were in higher organisms. Their work demonstrated that heritable variation in bacteria could be attributed to mechanisms similar to those in higher organisms. The previously puzzling ability of bacteria to respond rapidly and adaptively to changes in the environment could now be recognized as nothing more than the normal consequence of random gene mutation, followed by selection, in huge, rapidly reproducing populations.

Following this discovery, many researchers hurried to determine the range of true genetic mutation occurring in bacteria. Soon, such variation was detected in virtually every trait that could be studied, such as color, colony morphology, virulence (ability to infect a host), resistance to antimicrobial agents, nutritional requirements, and fermentation abilities (i.e., the ability to use different compounds as carbon sources).

Galton, Francis — 1889.

Natural Inheritance.

London: Macmillan

This is an image facsimile version of the entire 260-page original first edition.

Galton, Francis — 1889.

Natural Inheritance.

London: Macmillan

This is an image facsimile version of the entire 260-page original first edition.

Huxley, T. H. — 1869.

Nature: Aphorisms by Goethe.

Nature, 1:9-11.

PDF image facsimile file: 343,040 bytes - 3 pages

A special article, written by Huxley on request for the first issue of Nature, a new publication. The article is mainly a lengthy quote from Goethe, consisting of an extended rhapsody on "Nature."

Bridges, Calvin B. — 1916.

Non-disjunction as proof of the chromosome theory of heredity (part 1).

Genetics, B, 1:1-52.

PDF image facsimile file: 1.808,605 bytes - 52 pages - many figures

This paper was published as the first article in the first volume the new journal genetics. As the title states, the paper offered PROOF that genes are real, physical things that are carried on chromosomes.

This article was scanned from Alfred Sturtevant's personal copy of Genetics. Access to the journal was provided by Edward B. Lewis and Elliot M. Meyerowitz of the California Institute of Technology.

Bridges, Calvin B. — 1916.

Non-disjunction as proof of the chromosome theory of heredity (part 2).

Genetics, B, 1:107-163.

PDF image facsimile file: 2,600,250 bytes - 59 pages - many figures

This paper was published as the first article in the first volume the new journal genetics. As the title states, the paper offered PROOF that genes are real, physical things that are carried on chromosomes.

This article was scanned from Alfred Sturtevant's personal copy of Genetics. Access to the journal was provided by Edward B. Lewis and Elliot M. Meyerowitz of the California Institute of Technology.

McClung, C. E. — 1901.

Notes on the accessory chromosome.

Anatomischer Anzeiger, 20:220-226.

PDF typeset file: 58,569 bytes - 12 pages - no figures

In this brief paper, McClung introduces the evidence that male and female insects exhibit different chromosomal structures in their nuclei and that spermatozoa fall into two types - those that carry the "accessory chromosome" and those that do not.

Based on this analysis, McClung suggests that the presence or absence of the "accessory chromosome" in spermatozoa may determine the sex of the progeny. McClung published this short note in 1901 to alert the scientific community of his findings and to alert them to a more detailed argument that he had already submitted for publication elsewhere and that he knew would appear a year later, in McClung, C. E. 1902. The accessory chromosome - Sex determinant? Biological Bulletin, 3:43-84.

Mendel, Gregor — 1869.

On Hieracium-hybrids obtained by artificial fertilisation.

Verhandlungen des naturforschenden Vereines, Abhandlungen, Brünn, Bd. VIII für das Jahr 1869, 26-31. (Translated and reprinted as an appendix to Bateson, W. 1909. Mendel's Principles of Heredity. Cambridge University Press.)

PDF typeset file: 57,344 bytes - 8 pages - no figures

After his original paper on peas, Mendel published only one other paper on genetics, this one on Hieracium. Unknown to Mendel, Hieracium does not experience normal sexual fertilization, making it impossible for him to confirm the findings that he had obtained earlier with peas.

Castle, W. E., and Little, C. C. — 1910.

On a modified Mendelian ratio among yellow mice.

Science, N.S., 32:868-870.

PDF typeset file: 39,133 bytes - 7 pages - no figures

Here, Castle and Little offer evidence consistent with the idea that the gene for yellow fur in mice, studied earlier by Cuénot, is probably lethal when carried homozygously.

Aristotle. — 350 BC.

On the Generation of Animals.

This is a full-text PDF version of the entire book.

Any collection of critical works in the history of biology must include works by Aristotle.

Wright, Sewall — 1934.

On the Genetics of Subnormal Development of the Head (otocephaly) in the Guinea Pig

Genetics, 19: 471-505.

PDF image facsimile file

Wright, Sewall and Chase, Herman B. — 1936.

On the Genetics of the Spotted Pattern of the Guinea Pig

Genetics, 21: 758-787.

PDF image facsimile file

Darwin, C. — 1859.

On the Origin of Species.

London: John Murray, Albemarle Street.

This is a full-text PDF image facsimile version of the entire 502-page original first edition.

This is the book that changed the world and defined modern biology. By making mechanisms of heritable variation central to the biggest issue in all of biology, Darwin initiated the genetics revolution.

Aristotle. — 350 BC.

On the Parts of Animals.

This is a full-text PDF version of the entire book.

Any collection of critical works in the history of biology must include works by Aristotle. Here, in On the Parts of Animals, Aristotle provides one of the world's first efforts to understand life in terms of its component parts.

Vries, Hugo de, and Boedijn, K. — 1923.

On the distribution of mutant characters among the chromosomes of Oenothera lamarckiana.

Genetics, 8:233-238.

PDF image facsimile file: 6 pages

Wallace. A. R. — 1855.

On the law which has regulated the introduction of new species.

Annals and Magazine of Natural History, 2nd Series. 16:184-196.

PDF typeset file: 90,845 bytes - 17 pages - no figures

Today Darwin's name is known to everyone, while Alfred Russel Wallace is familiar to only a few. Yet the concept of evolution by natural selection was independently developed by Wallace and Darwin, with Wallace publishing first. This paper, and the 1858 manuscript he sent directly to Darwin, show clearly that, prior to Darwin's publication, Wallace had a firm grasp on the concept of evolution.

Sutton, Walter S. — 1902.

On the morphology of the chromosome group in Brachystola magna.

Biological Bulletin, 4:24-39.

PDF typeset file: 119,906 bytes - 18 pages - 11 figures

In this paper, Sutton reports cytological studies of grasshopper chromosomes that lead him to conclude that (a) chromosomes have individuality, (b) that they occur in pairs, with one member of each pair contributed by each parent, and (c) that the paired chromosomes separate from each other during meiosis.

After presenting considerable evidence for his assertions, Sutton closes his paper with a sly reference to its undoubted significance:

I may finally call attention to the probability that the association of paternal and maternal chromosomes in pairs and their subsequent separation during the reducing division as indicated above may constitute the physical basis of the Mendelian law of heredity. To this subject I hope soon to return in another place.

Wright, Sewall — 1918.

On the nature of size factors.

Genetics, 3:367-374.

PDF image facsimile file: 8 pages - 0 figures

Darbishire, A. D. — 1905.

On the supposed antagonism of Mendelian to biometric theories of heredity.

Manchester Memoirs, 49:1-19.

PDF typeset file: 16 pages

Morgan, L. V. — 1925.

Polyploidy in drosophila Melanogaster with Two Attached X Chromosomes

Genetics, 10: 148-178.

PDF image facsimile file

Sturtevant, A. H. — 1936.

Preferential Segregation in Triplo-IV Females of Drosophila Melanogaster

Genetics, 21: 444-466.

PDF image facsimile file

Bateson, William. — 1900.

Problems of heredity as a subject for horticultural investigation.

Journal of the Royal Horticultural Society, 25:54-61.

PDF typeset file: 84,218 bytes - 12 pages - no figures

Mendel's work of 1865 was largely neglected, until 1900 when it was simultaneously rediscovered by Hugo de Vries, Carl Correns, and Erik von Tschermak. When Mendel's work came to the attention of William Bateson (who himself had already been advocating controlled crosses as an approach to studying heredity), he was convinced that Mendel's work was of major importance:

That we are in the presence of a new principle of the highest importance is, I think, manifest. To what further conclusions it may lead us cannot yet be foretold.

Bateson devoted the remainder of his scientific career to further elucidations of "Mendelism." This present paper captures the enthusiasm of Bateson's first encounter with the works of Mendel.

Jones, Donald F. (ed) — 1932.

Proceedings of the Sixth International Congress of Genetics, Vol. I.

Austin, Texas: Genetics Society of America

This is an image facsimile version of the entire 396-page original edition.

The Proceedings of the Sixth International Congress of Genetics, held in 1932, offers a glimpse into classical genetics at the height of its power and influence. Thomas Morgan, who had just received the first Nobel Prize ever awarded in genetics, served as president of the congress.

The participants list reads like a who's who of classical genetics: The three rediscovers of Mendel - Correns, de Vries, and von Tschermak - all attended the meeting. Morgan, Sturtevant, and Muller gave talks. Population genetics and the relationship of genetics to evolution was discussed by R. A. Fisher, J. B. S. Haldane, and Sewall Wright.

According to the Treasurer's Report, the total cost of the meeting was $17,583.58.

Cook, O. F. — 1909.

Pure Strains as Artifacts of Breeding

The American Naturalist 43: 241-242.

Morgan, Thomas H. — 1911.

Random segregation versus coupling in Mendelian inheritance

Science, 34:384.

PDF image facsimile file: 189,193 bytes - 1 page

Morgan, Thomas H. — 1909.

Recent Experiments on the Inheritance of Coat Colors in Mice

The American Naturalist 43: 494-510.

Woods, F. A. — 1908.

Recent Studies in Human Heredity

The American Naturalist 42: 685-693.

Wilson, Edmund B. — 1909.

Recent researches on the determination and heredity of sex.

Science, NS 29:53-70.

PDF image facsimile file: 18 pages

Crew, F. A. E. — 1969.

Recollections of the early days of the genetical society.

In John Jinks, The Genetical Society - The First Fifty Years, Edinburgh: Oliver and Boyd, pp.9-15.

PDF image facsimile file: 7 pages

Bridges, C. B. and Bridges, P. N. — 1938.

Salivary Analysis of Inversion-3r-payne in the "venation" Stock of Drosophila melanogaster

Genetics, 23: 111-114.

PDF image facsimile file

Wilson, Edmund B. — 1909.

Secondary chromosome-couplings and the sexual relations in Abraxas.

Science, NS 29:704-706.

PDF image facsimile file: 3 pages

Davenport, C. B. — 1930.

Sex linkage in man

Genetics, 15: 401-444.

PDF image facsimile file

Morgan, Thomas H. — 1910.

Sex-limited inheritance in Drosophila.

Science, 32:120-122.

PDF typeset file: 72,823 bytes - 14 pages - no figures

After Mendel's work was rediscovered in 1900, many researchers worked to confirm and extend his findings. Although a possible relationship between genes and chromosomes was suggested almost immediately, proof of that relationship, or even evidence that genes were physical objects, remained elusive. To many, the gene served only as a theoretical construct, conveniently invoked to explain observed inheritance patterns. In 1909, Morgan himself published a paper in which he expressed his skepticism about the facility with which Mendelian explanations were adjusted to fit the facts.

Just one year later, however, Morgan published the results of his work on an atypical male fruit fly that appeared in his laboratory, and all this began to change. Normally Drosophila melanogaster have red eyes, but Morgan's new fly had white eyes. The inheritance pattern for this new eye-color trait suggested strongly that the gene for eye-color was physically attached to the X-chromosome. In the paper, Morgan concluded:

It now becomes evident why we found it necessary to assume a coupling of [the eye-color gene] and X in one of the spermatozoa of the red-eyed F1 hybrid. The fact is that this R and X are combined, and have never existed apart.

In this present paper, Morgan offered the first evidence that genes are real, physical objects, located on chromosomes, with properties that could be manipulated and studied experimentally. The white-eyed fly provided the foundation upon which Morgan and his students established the modern theory of the gene.

Macarthur, John W. — 1933.

Sex-linked Genes in the Fowl

Genetics, 18: 210-220.

PDF image facsimile file

Morgan, Thomas H. — 1913.

Simplicity versus adequacy in Mendelian formulae

The American Naturalist, 47:372-374

PDF typeset file: 32,835 bytes - 6 pages - no figures

Soon after Mendel was rediscovered, the nature of the gene was being worked out. Along the way, many suggested changes to the symbology being used (e.g., B for dominant allele, b for recessive). Here Morgan offers some thoughts on changing Mendelian symbols.

Castle, W. E. — 1913.

Simplification of Mendelian formulae.

The American Naturalist, 47:170-182

PDF typeset file: 69,294 bytes - 13 pages - no figures

Soon after Mendel was rediscovered, the nature of the gene was being worked out. Along the way, many suggested changes to the symbology being used (e.g., B for dominant allele, b for recessive). Here Castle offers some suggestions for changing Mendelian symbols.

Metz, C. W. — 1937.

Small Deficiencies and the Problem of Genetic Units in the Giant Chromosomes

Genetics, 22: 543-556.

PDF image facsimile file

Gager, Charles Stuart — 1908.

Some Physiological Effects of Radium Rays

The American Naturalist 42: 761-778.

Spillman, W. J. — 1908.

Spurious Allelomorphism: Results of Some Recent Investigations

The American Naturalist

Stevens, Nettie M. — 1906.

Studies in Spermatogenesis Part II., A comparative study of the heterochromosomes in certain species of coleoptera, hemiptera and lepidoptera, with especial reference to sex determination.

Carnegie Institution of Washington, Publication No. 36, part II., pp 1-43.

PDF image facsimile file: 1,936,652 bytes - 43 pages - 8 plates

Stevens, Nettie M. — 1905.

Studies in Spermatogenesis with especial reference to the "accessory chromosome".

Carnegie Institution of Washington, Publication No. 36., pp 1-33.

PDF image facsimile file: 1,448,192 bytes - 33 pages - 7 plates

Castle, W. E. and Reed, S. C. — 1936.

Studies of Inheritance in Lop-eared Rabbits

Genetics, 21: 297-309.

PDF image facsimile file

Castle, W. E., Gates, W. H., and Reed, S. C. — 1936.

Studies of a Size Cross in Mice

Genetics, 21: 66-78.

PDF image facsimile file

Castle, W. E., Gates, W. H., Reed, S. C. and Law, L. W. — 1936.

Studies of a Size Cross in Mice, II

Genetics, 21: 310-323.

PDF image facsimile file

Dobzhansky, Th. and Beadle, G. W. — 1936.

Studies on Hybrid Sterility IV. Transplanted Testes in Drosophila Pseudoobscura

Genetics, 21: 832-840.

PDF image facsimile file

Dobzhansky, Th. — 1936.

Studies on Hybrid Sterility. II. Localization of Sterility Factors in Drosophila Pseudoobscura Hybrids

Genetics, 21: 113-135.

PDF image facsimile file

East, E. M. — 1916.

Studies on Size Inheritance in Nicotiana

Genetics, 1:164-176.

PDF image facsimile file

Stevens, Nettie M. — 1906.

Studies on the germ cells of aphids.

Carnegie Institution of Washington, Publication No. 51., pp 1-28.

PDF image facsimile file: 1,180,954 bytes - 28 pages - 4 plates

Wright, Sewall — 1921.

Systems of mating. I. The biometric relations between parent and offspring.

Genetics, 6:111-123.

PDF image facsimile file: 13 pages - 2 figures

Wright, Sewall — 1921.

Systems of mating. II. The effects of inbreeding on the genetic composition of a population.

Genetics, 6:124-143.

PDF image facsimile file: 20 pages - 12 figures

Wright, Sewall — 1921.

Systems of mating. III. Assortative mating based on somatic resemblance.

Genetics, 6:144-161.

PDF image facsimile file: 18 pages - 7 figures

Wright, Sewall — 1921.

Systems of mating. IV. The effects of selection.

Genetics, 6:162-166.

PDF image facsimile file: 5 pages - 1 figure

Wright, Sewall — 1921.

Systems of mating. V. General considerations.

Genetics, 6:167-178.

PDF image facsimile file: 12 pages - 7 figures

Shull, A. Franklin — 1922.

Ten Years of Heredity.

Transactions of the American Microscopical Society, 41:82-100.

PDF image facsimile file: 909,722 bytes - 19 pages - 8 figures

Shull, George Harrison — 1909.

The "Presence and Absence" Hypothesis.

The American Naturalist, 43:410-419.

PDF image facsimile file: 655,705 bytes - 10 pages - 0 figures

Mendel - de Vries - Correns - Tschermak — 1950.

The Birth of Genetics

Special supplement to the journal Genetics 35(5, pt 2): 1-48.

PDF typeset file: 344,064 bytes - 66 pages - no figures

To celebrate the fiftieth anniversary of the rediscovery of Mendel's work, the Genetics Society of America published this special supplement, containing translations of the original papers by the rediscovers of Mendel - Carl Correns, Erik von Tschermak, and Hugo de Vries. It also contains letters written by Mendel and sent to Carl Nägeli, a leading botanist.

This was the first time these key works were made available in English translation.

Wilson, Edmund B. — 1900.

The Cell in Development and Inheritance, 2nd Edition

New York: The Macmillan Company

This is a full-text PDF image facsimile version of the entire 490-page original book.

Edmund B. Wilson was the leading cytologist of his time and The Cell in Development and Inheritance was the definitive text on cytology from 1896 into the 1930's. A modern reader will be surprised to see how many of the illustrations in the book seem familiar – versions of many of them still appear in textbooks of introductory biology.

The last chapter in the book is entitled "Theories of Inheritance and Development:, and it begins:

Every discussion of inheritance and development must take as its point of departure the fact that the germ is a single cell similar in its essential nature to any one of the tissue-cells of which the body is composed. That a cell can carry with it the sum total of the heritage of the species, that it can in the course of a few days or weeks give rise to a mollusk or a man, is the greatest marvel of biological science. In attempting to analyze the problems that it involves, we must from the outset hold fast to the fact, on which Huxley insisted, that the wonderful formative energy of the germ is not impressed upon it from without, but is inherent in the egg as a heritage from the parental life of which it was originally a part. The development of the embryo is nothing new. It involves no breach of continuity, and is but a continuation of the vital processes going on in the parental body. What gives development its marvelous character is the rapidity with which it proceeds and the diversity of the results attained in a span so brief.

But when we have grasped this cardinal fact, we have but focussed our instruments for a study of the real problem. How do the adult characteristics lie latent in the germ-cell; and how do they become patent as development proceeds? This is the final question that looms in the background of every investigation of the cell. In approaching it we may well make a frank confession of ignorance; for in spite of all that the microscope has revealed, we have not yet penetrated the mystery, and inheritance and development still remain in their fundamental aspects as great a riddle as they were to the Greeks. What we have gained is a tolerably precise acquaintance with the external aspects of development. The gross errors of the early preformationists have been dispelled.' We know that the germ-cell contains no predelineated embryo; that development is manifested, on the one hand, by the cleavage of the egg, on the other hand, by a process of differentiation, through which the products of cleavage gradually assume diverse forms and functions, and so accomplish a physiological division of labour. We can clearly recognize the fact that these processes fall in the same category as those that take place in the tissue-cells; for the cleavage of the ovum is a form of mitotic cell-division, while, as many eminent naturalists have perceived, differentiation is nearly related to growth and has its root in the phenomena of nutrition and metabolism. The real problem of development is the orderly sequence and correlation of these phenomena toward a typical result. We cannot escape the conclusion that this is the outcome of the organization of the germ-cells; but the nature of that which, for lack of a better term, we call "organization," is and doubtless long will remain almost wholly in the dark.

East - Morgan - Harris - Shull — 1923.

The Centenary of Gregor Mendel and of Francis Galton.

The Scientific Monthly, 16: 225-270.

PDF typeset file: 247,951 bytes - 54 pages - no figures

In December of 1922, the American Society of Naturalists held a special session to honor the centenaries of the birth of Gregor Mendel and of Francis Galton. This is the collection of the four papers presented at that session and later published in the The Scientific Monthly.

Morgan, Thomas H. — 1915.

The Constitution of the Hereditary Material.

Proceedings of the American Philosophical Society, 54:143-153.

PDF image facsimile file: 424,504 bytes - 11 pages - 4 figures

Morgan, Thomas Hunt — 1897.

The Development of the Frog's Egg: An Introduction to Experimental Embryology.

New York: The Macmillan Company

PDF image facsimile file: 46,153,994 bytes - 204 pages - several figures

Thomas Hunt Morgan is best known for his work in genetics, for which he received the Nobel Prize in 1933. Morgan's first research interest, however, was in embryology. This short book on frog development is his first book.

From the Preface: The development of the frog's egg was first made known through the studies of Swammerdam, Spallanzani, Rusconi, and von Baer. Their work laid the basis for all later research. More recently the experiments of Pfluger and of Roux on this egg have turned the attention of embryologists to the study of development from an experimental standpoint. Owing to the ease with which the frog's egg can be obtained, and its tenacity of life in a confined space, as well as its suitability for experimental work, it is an admirable subject with which to begin the study of vertebrate development. In the following pages an attempt is made to bring together the most important results of studies of the development of the frog's egg. I have attempted to give a continuous account of the development, as far as that is possible, from the time when the egg is forming to the moment when the young tadpole issues from the jelly-membranes. Especial weight has been laid on the results of experimental work, in the belief that the evidence from this source is the most instructive for an interpretation of the development. The evidence from the study of the normal development has, however, not been neglected, and wherever it has been possible I have attempted to combine the results of experiment and of observation, with the hope of more fully elucidating the changes that take place. Occasionally departures have been made from the immediate subject in hand in order to consider the results of other work having a close bearing on the problem under discussion. I have done this in the hope of pointing out more definite conclusions than could be drawn from the evidence of the frog's egg alone.

Beadle, G. W. and Ephrussi, Boris — 1936.

The Differentiation of Eye Pigments in Drosophila As Studied by Transplantation

Genetics, 21: 225-247.

PDF image facsimile file

East, Edward M. — 1909.

The Distinction between Development and Heredity in Inbreeding.

The American Naturalist 43: 173-181.

Fisher, R. A. — 1919.

The Genesis of Twins

Genetics, 4: 489-499.

PDF image facsimile file

Altenburg, Edgar and Muller, Hermann J. — 1920.

The Genetic Basis of Truncate Wing,—an Inconstant and Modifiable Character in Drosophila

Genetics, 5: 248.

PDF image facsimile file

Altenburg, Edgar and Muller, Hermann J. — 1920.

The Genetic Basis of Truncate Wing,—an Inconstant and Modifiable Character in Drosophila

Genetics, 5: 1-59.

PDF image facsimile file

Fisher, R. A. , Immer, F. R., and Tedin, Olof — 1932.

The Genetical Interpretation of Statistics of the Third Degree in the Study of Quantitative Inheritance

Genetics, 17: 107-124.

PDF image facsimile file

Weismann, August — 1893.

The Germ-Plasm.

New York: Charles Scribner's Sons

This is a full-text PDF image facsimile version of the entire 477-page original book.

August Weismann was one of the most influential biologists of the late nineteenth century. In The Germ-Plasm he lays out a new theory of heredity, one based on the continuity of the germ-plasm (the gametes and the cells that give rise to the gametes) as opposed to the finite existence of the soma (the cells of the body).

Weismann introduces his book modestly:

Any attempt at the present time to work out a theory of heredity in detail may appear to many premature, and almost presumptuous: I confess there have been times when it has seemed so even to myself. I could not, however, resist the temptation to endeavour to penetrate the mystery of this most marvellous and complex chapter of life as far as my own ability and the present state of our knowledge permitted.

A key point in his theory is that it makes impossible the inheritance of acquired characteristics, and thus deals a death blow to Lamarckism, as well as to Darwin's pangenesis:

What first struck me when I began seriously to consider the problem of heredity, some ten years ago, was the necessity for assuming the existence of a special organised and living hereditary substance, which in all multicellular organisms, unlike the substance composing the perishable body of the individual, is transmitted from generation to generation. This is the theory of the continuity of the germ-plasm. My conclusions led me to doubt the usually accepted view of the transmission of variations acquired by the body (soma); and further research, combined with experiments, tended more and more to strengthen my conviction that in point of fact no such transmission occurs.

Aristotle. — 350 BC.

The History of Animals.

This is a full-text PDF version of the entire book.

Any collection of critical works in the history of biology must include works by Aristotle. Here, in The History of Animals, Aristotle provides a discussion of the diversity of life, with considerable attention to reproduction and heredity.

Taliaferro, W. H., and Huck, J. G. — 1923.

The Inheritance of Sickle-cell Anaemia in Man

Genetics, 8: 594-598.

PDF image facsimile file

Snyder, Laurence H. — 1924.

The Inheritance of the Blood Groups

Genetics, 9: 465-478.

PDF image facsimile file

Bridges, Calvin B. and Mohr, Otto L. — 1919.

The Inheritance of the Mutant Character "vortex"

Genetics, 4: 283-306.

PDF image facsimile file

Brooks, W. K. — 1883.

The Law of Heredity, Second Edition.

Baltimore and New York: John Murphy & Co., Publishers.

This is a full-text PDF image facsimile version of the entire 336-page original first edition.

It is often thought that, besides Mendel, little work on heredity occurred during the 19th Century. This is far from true. Darwin's Origin of Species placed the study of inherited variation at the center of biological thought. As this work by Brooks attests, considerable effort was made to understand heredity, especially as it related to natural selection.

Although the details of Brooks' analysis are now outdated, the book provides general insights into late-nineteenth Century thinking on heredity. Since Brooks was one of T. H. Morgan's instructors when Morgan was a student at Johns Hopkins, the book also provides insights into the specific instruction on heredity that was presented to the man who became the first recipient of a Nobel Prize for work on genetics.

NOTE: This is an electronic FACSIMILE of the original work. The PDF files contain images of the original pages. The files are large and will download slowly. It is probably best to download the files to disk for later viewing and printing. When printed, these files give output equivalent to good quality Xerox copies of the original.

Charles W. Metz, Charles W. — 1918.

The Linkage of Eight Sex-linked Characters in Drosophila virilis

Genetics, 3: 107-134.

PDF image facsimile file

Muller, Hermann J. — 1916.

The Mechanism of Crossing-over.

New York: The American Naturalist

This is an image facsimile version of the entire 86-page original edition.

Beginning 1910, T. H. Morgan and his students established the foundations of modern genetics by demonstrating that genes were real — not theoretical — entities.

This work is a collection of papers that represented the doctoral dissertation of one of those students - H. J. Muller.

Morgan, Thomas H., Sturtevant, A. H., Muller, H. J., and C. B. Bridges — 1915.

The Mechanism of Mendelian Heredity.

New York: Henry Holt and Company

This is a full-text PDF image facsimile version of the entire 262-page original book.

This book, by T. H. Morgan and his students, is the first work to articulate a comprehensive, mechanistic model to explain Mendelian patterns of inheritance.

Although Mendelism had quickly been accepted as a good phenomenological explanation for the patterns seen in Mendelian crosses, until the work of Morgan's group, it was still possible to consider Mendelism to be a purely theoretical model of heredity. As Morgan's group first established the relationship of genes to chromosomes, then developed the first genetic map, and went on to describe a variety of interactions between chromosomes and Mendelian factors, the conclusions they offered became inescapable - genes are physical objects, carried on chromosomes in static locations.

Morgan's group made genes real and this book is the first full-length presentation of their findings. It revolutionized the study of heredity.

Patterson, J. T. — 1933.

The Mechanism of Mosaic Formation in Drosophila

Genetics, 18: 32-52.

PDF image facsimile file

Bateson, William. — 1908.

The Methods and Scope of Genetics.

London: Cambridge University Press.

This is a newly typeset full-text version of the entire 49-page original first edition.

This short book is a copy of the Inaugural Address, given by Bateson upon the creation of the Professorship of Biology at Cambridge. In his introduction, Bateson notes:

The Professorship of Biology was founded in 1908 for a period of five years partly by the generosity of an anonymous benefactor, and partly by the University of Cambridge. The object of the endowment was the promotion of inquiries into the physiology of Heredity and Variation, a study now spoken of as Genetics.

It is now recognized that the progress of such inquiries will chiefly be accomplished by the application of experimental methods, especially those which Mendel's discovery has suggested. The purpose of this inaugural lecture is to describe the outlook over this field of research in a manner intelligible to students of other parts of knowledge.

Here then is a view of how one of the very first practitioners of genetics conceived of the "Methods and Scope of Genetics".

Painter, Theophilus S. — 1934.

The Morphology of the X Chromosome in Salivary Glands of Drosophila melanogaster and a New Type of Chromosome Map for this Element.

Genetics, 19: 448-469.

PDF image facsimile file: 1,519,775 bytes - 22 pages - 2 figures

In this paper, Painter follows up on his earlier publication describing Drosophila giant salivary-gland chromosomes and here shows how genetics maps, obtained from crossing studies, can be placed on a morphological map obtained from cytological studies.

Bridges, Calvin B., and Olbrycht, T. M. — 1926.

The Multiple Stock "xple" and its use.

Genetics, 11:41-55.

PDF image facsimile file: 16 pages

Stern, Curt and Bridges, Calvin B. — 1926.

The Mutants of the Extreme Left End of the Second Chromosome of Drosophila melanogaster

Genetics, 11: 503-530.

PDF image facsimile file

Spillman, W. J. — 1909.

The Nature of "Unit" Characters

The American Naturalist 43: 243-248.

Davis, Bradley M. — 1909.

The Permanence of Chromosomes in Plant Cells

The American Naturalist

Morgan, Thomas H. — 1919.

The Physical Basis of Heredity.

Philadelphia: J. B. Lippincott Company

This is a full-text PDF image facsimile version of the entire 305-page original book.

In this book, T. H. Morgan (who would later receive the first Nobel Prize for genetics research) describes the model of heredity developed at Columbia by Morgan and his students.

The foundations of genetics were laid down by Mendel, and these were brought to the world's attention when his work was rediscovered by Correns, de Vries, and von Tschermak in 1900. But the real establishment of genetics as a real science, with a known physical basis, did not occur until the work outlined in this book became generally known.

To understand the true conceptual underpinnings of classical genetics, one must read the publications from "The Fly Room" at Columbia.

Castle, W. E. — 1938.

The Relation of Albinism to Body Size in Mice

Genetics, 23: 269-274.

PDF image facsimile file

Little, C. C. — 1917.

The Relation of Yellow Coat Color and Black-eyed White Spotting of Mice in Inheritance

Genetics, 2: 433-444.

PDF image facsimile file

Schultz, Jack, and Dobzhansky, Th. — 1934.

The Relation of a Dominant Eye Color in Drosophila Melanogaster to the Associated Chromosome Rearrangement

Genetics, 19: 344-364.

PDF image facsimile file

Sturtevant, A. H. and Beadle, G. W. — 1936.

The Relations of Inversions in the X Chromosome of Drosophila Melanogaster to Crossing Over and Disjunction

Genetics, 21: 554-604.

PDF image facsimile file

Wright, Sewall — 1934.

The Results of Crosses Between Inbred Strains of Guinea Pigs, Differing in Number of Digits

Genetics, 19: 537-551.

PDF image facsimile file

Muller, H. J. and Jacobs-Muller, Jessie M. — 1925.

The Standard Errors of Chromosome Distances and Coincidence

Genetics, 10: 509-524.

PDF image facsimile file

Painter, Theophilus S. and Griffen, Allen B. — 1937.

The Structure and the Development of the Salivary Gland Chromosomes of Simulium

Genetics, 22: 612-633.

PDF image facsimile file

Weinstein, Alexander — 1936.

The Theory of Multiple-strand Crossing Over

Genetics, 21: 490.

PDF image facsimile file

Weinstein, Alexander — 1936.

The Theory of Multiple-strand Crossing Over

Genetics, 21: 155-199.

PDF image facsimile file

Morgan, Thomas H. — 1928.

The Theory of the Gene, Revised and Enlarged Edition.

New Haven: Yale University Press

This is a full-text PDF image facsimile version of the entire 358-page original book.

This book, by T. H. Morgan, summarizes the state of knowledge on classical genetics in the mid 1920's.

Although Mendelism had quickly been accepted as a good phenomenological explanation for the patterns seen in Mendelian crosses, until the work of Morgan's group, it was still possible to consider Mendelism to be a purely theoretical model of heredity. As Morgan's group first established the relationship of genes to chromosomes, then developed the first genetic map, and went on to describe a variety of interactions between chromosomes and Mendelian factors, the conclusions they offered became inescapable – genes are physical objects, carried on chromosomes in static locations.

Less than 15 years after Morgan first started working with fruit flies, the foundations for a theory of the gene had been worked out – largely by Morgan and students working in his laboratory.

Morgan, Thomas H. — 1917.

The Theory of the Gene.

The American Naturalist, 51:513-544.

PDF typeset file: 3,116,439 bytes - 28 pages - 9 figures

In 1909, Morgan expressed doubts about the methods of Mendelian inheritance. Then, in 1910, a white-eyed mutant fly turned up in Morgan’s laboratory and studies on the inheritance of the white-eyed trait suggested that the gene producing the trait was carried on the X-chromosome. This strongly suggested that Mendelian genes were real, not th The Mechanism of Mendelian Heredity.

In this paper, Morgan discusses The Theory of the Gene, as established in his laboratory.

Stadler, L. J. — 1926.

The Variability of Crossing Over in Maize

Genetics, 11: 1-37.

PDF image facsimile file

Darwin, C. — 1883.

The Variation of Animals and Plants Under Domestication, Second Edition, Revised (two volumes).

New York: D. Appleton & Co.

This is a full-text PDF image facsimile version of the entire 473-page volume I and the entire 495-page volume II of the original work.

Although Darwin's theories regarding the origin of species through natural selection required that some mechanism of heredity exist, no such mechanism was known when the Origin was written. After the Origin appeared, Darwin turned his attention to the mechanism(s) of heredity, resulting in his subsequent two-volume The Variation of Animals and Plants Under Domestication.

In volume I, Darwin summarized what was known about inheritance in a variety of domesticated species and concluded with a chapter, Inheritance, that begins his general summary of the mechanisms of inheritance. He continued this summary in volume II, which also offers Darwin's own theory of inheritance in Chapter XXVII, Provisional Hypothesis of Pangenesis.

The notion of pangenesis dominated late nineteenth-century thinking about inheritance. Although ultimately seen to be simply wrong, it was very influential and a familiarity with its tenets is essential for anyone wishing to understand the intellectual climate at the time Mendel was rediscovered in 1900.

NOTE: This is an electronic FACSIMILE of the original work. The PDF files contain images of the original pages. The files are large and will download slowly. It is probably best to download the files to disk for later viewing and printing. When printed, these files give output equivalent to good quality Xerox copies of the original.

Darwin, C. — 1845.

The Voyage of the Beagle, Second Edition.

London: John Murray.

This is a full-text, newly typeset, PDF version of the entire book.

For five years, from 1831-1836, Charles Darwin served as the official naturalist aboard the HMS Beagle as it visited exotic locations around the world. During this voyage, Darwin first came to wonder about the mechanisms driving the origin of species. This book chronicles the voyage and documents his early thinking.

Dobzhansky, Th. — 1935.

The Y Chromosome of Drosophila Pseudoobscura

Genetics, 20: 366-376.

PDF image facsimile file

McClung, C. E. — 1902.

The accessory chromosome - Sex determinant?

Biological Bulletin, 3:43-84.

PDF typeset file: 188,601 bytes - 40 pages - no figures

In this paper, McClung analyzes the evidence that male and female insects exhibit different chromosomal structures in their nuclei and that spermatozoa fall into two types - those that carry the "accessory chromosome" and those that do not.

Based on this analysis, McClung offers the bold hypothesis that the presence or absence of the "accessory chromosome" in spermatozoa may determine the sex of the progeny:

A most significant fact ... is that the [accessory chromosome] is apportioned to but one half of the spermatozoa. Assuming it to be true that the chromatin is the important part of the cell in the matter of heredity, then it follows that we have two kinds of spermatozoa that differ from each other in a vital matter. We expect, therefore, to find in the offspring two sorts of individuals in approximately equal numbers. ... [Since] nothing but sexual characters ... divides the members of a species into two well-defined groups, ... we are logically forced to the conclusion that the [accessory] chromosome has some bearing upon this arrangement.

That is, McClung hypothesizes that a difference in chromosome number is the cause, not an effect, of sex determination. This paper represents the first effort to associate the determination of a particular trait with a particular chromosome.

Morgan, Thomas H. — 1923.

The bearing of Mendelism on the origin of species.

The Scientific Monthly, 16: 237-247.

PDF typeset file: 247,951 bytes - 54 pages - no figures

In December of 1922, the American Society of Naturalists held a special session to honor the centenaries of the birth of Gregor Mendel and of Francis Galton. This is one of the four papers presented at that session and later published in the The Scientific Monthly.

Sutton, Walter S. — 1903.

The chromosomes in heredity.

Biological Bulletin, 4: 231-251.

PDF typeset file: 133,686 bytes - 20 pages - no figures

Early on, some researchers noticed that Mendel's theory required that some kind of hereditary unit segregate in pairs to offspring. Sutton was one of the first to note that the chromosomes behaved in exactly a manner to match this requirement.

The opening lines of his paper show that he is aware of the significance of his observations:

In a recent announcement of some results of a critical study of the chromosomes in the various cell generations of Brachystola the author briefly called attention to a possible relation between the phenomena there described and certain conclusions first drawn from observations on plant hybrids by Gregor Mendel in 1865, and recently confirmed by a number of able investigators. Further attention has already been called to the theoretical aspects of the subject in a brief communication by Professor E. B. Wilson. The present paper is devoted to a more detailed discussion of these aspects, the speculative character of which may be justified by the attempt to indicate certain lines of work calculated to test the validity of the conclusions drawn. The general conceptions here advanced were evolved purely from cytological data, before the author had knowledge of the Mendelian principles, and are now presented as the contribution of a cytologist who can make no pretensions to complete familiarity with the results of experimental studies on heredity. As will appear hereafter, they completely satisfy the conditions in typical Mendelian cases, and it seems that many of the known deviations from the Mendelian type may be explained by easily conceivable variations from the normal chromosomic processes.

Wilson, Edmund B. — 1905.

The chromosomes in relation to the determination of sex in insects.

Science, N.S. 22:500-502.

PDF typeset file: 43,282 bytes - 8 pages - no figures

In this short note, Wilson (a leading cell biologist of his time) offers his endorsement of the idea that there is a relationship between specific chromosomes and the determination of sex in insects:

Material procured during the past summer demonstrates with great clearness that the sexes of Hemiptera show constant and characteristic differences in the chromosome groups, which are of such a nature as to leave no doubt that a definite connection of some kind between the chromosomes and the determination of sex exists in these animals. These differences are of two types. In one of these, the cells of the female possess one more chromosome than those of the male; in the other, both sexes possess the same number of chromosomes, but one of the chromosomes in the male is much smaller than the corresponding one in the female (which is in agreement with the observations of Stevens on the beetle Tenebrio).

Wilson's contribution is the observation that the various cases all seem to fall cleanly into one of two types — those in which the male seems to be missing a chromosome, and those in which the male is carrying a pair of mis-matched chromosomes. Wilson's goes on to note that he does not believe that the 'accessory chromosomes' are actual sex determinants as conjectured by McClung, but rather that they probably act in a quantitative, not qualitative manner.

Wilson's endorsement of the idea that chromosome make-up is related to sex determination greatly facilitated the later general acceptance of the notion that individual chromosomes might be related to individual traits. Of course, sex is not a simple Mendelian trait, such as round or wrinkled peas, but nonetheless the evidence that some aspect of phenotype (sex) was related to some aspect of genotype was an important initial step in bringing genetics together with cytology.

East, E. M. — 1929.

The concept of the gene.

Proceedings of the International Congress of Plant Sciences, Ithaca, New York, August 16-23, 1926, vol. 1. Menasha, WI: George Banta Publishing Co. pp 889-895.

PDF typeset file: 76,104 bytes - 11 pages - no figures

As classical genetics acquired more and more explanatory power, the question what is a gene? became more important. Were genes real physical entities, or merely theoretical concepts that allowed for the mathematical modelling of inheritance. This paper represents one effort to consider The concept of the gene. The paper's opening paragraph sets the tone:

Nearly fifteen years ago I attempted to defend the thesis that the Mendelian method of recording the facts of inheritance was simply a notation useful as a description of physiological facts. The argument was an elaboration of the proposition that the germ-cell unit of heredity, the gene, was an abstract, formless, characterless concept used for convenience in describing the results of breeding experiments. It was the ghost of an entity which might later be clothed with flesh, but its usefulness at the time was due to its adaptability to mathematical treatment. By postulating that the results derived from controlled matings were due to the activities of definite germ-cell units which could be manipulated arithmetically, investigators were able to formulate new experimental tests, and thus to open the way to further discovery; but these units could be given no intelligible interpretation in terms of geometry, chemistry, or physiology.

In the last paragraph, East asserts:

We arrive, therefore, at the same port from which we departed when our discussion began. The genes are units useful in concise descriptions of the phenomena of heredity. Their place of residence is the chromosomes. Their behavior brings about the observed facts of genetics. For the rest, what we know about them is merely an interpretation of crossover frequency. In terms of geometry, chemistry, physics or mechanics, we can give them no description whatever.

McClintock, Barbara and Hill, Henry E. — 1931.

The cytological identification of the chromosome associated with the r-g linkage group in Zea mays

Genetics, 16: 175-190.

PDF image facsimile file

Wright, Sewall — 1927.

The effects in combination of the major color-factors of the guinea pig

Genetics, 12: 530-569.

PDF image facsimile file

Sturtevant, Alfred H. — 1925.

The effects of unequal crossing over at the bar locus in Drosophila.

Genetics, 10:117-147.

PDF image facsimile file: 31 pages - 10 figures

Wright, Sewall — 1925.

The factors of the albino series of guinea-pigs and their effects on black and yellow pigmentation.

Genetics, 10:223-260.

PDF image facsimile file: 38 pages - 5 figures

Bateson, William, and Saunders, E. R. — 1902.

The facts of heredity in the light of Mendel's discovery.

Reports to the Evolution Committee of the Royal Society, I, 1902, pp. 125-160

PDF typeset file: 543,744 bytes - 41 pages - no figures

William Bateson was the first English-speaking scientist to appreciate the potential significance of Mendel's work. He began working immediately to confirm and extend Mendel's findings. This report to the evolution committee of the Royal Society represents one of the very first systematic investigations into Mendelism as a possible general explanation for the fundamental mechanisms of heredity.

Muller, Hermann J., and Altenburg, Edgar. — 1930.

The frequency of translocations produced by X-rays in Drosophila.

Genetics, 15:283-311.

PDF image facsimile file: 29 pages

Garrod, Archibald E. — 1902.

The incidence of alkaptonuria: A study in chemical individuality.

Lancet, ii:1616-1620.

PDF typeset file: 145,052 bytes - 18 pages - no figures

This paper is a true classic. Like Mendel's own work, this report offers insights so far ahead of its time that it, and Garrod's follow-on work, were largely neglected, until later efforts to elucidate the physiological functioning of genes led to the Nobel-prize-winning one-gene, one-enzyme hypothesis.

Less than two years after the rediscovery of Mendelism and just a few years after the word biochemistry was first coined, Garrod reports on alkaptonuria in humans and comes to the conclusion that it is inherited as a Mendelian recessive and that the occurrence of mutations (sports in the word of the time) in metabolic function should be no more surprising than inherited variations in morphology.

Bridges, Calvin B., and Mohr, Otto L. — 1919.

The inheritance of the mutant character "vortex".

Genetics, 4:283-306.

PDF image facsimile file: 24 pages

Sturtevant, Alfred H. — 1913.

The linear arrangement of six sex-linked factors in Drosophila, as shown by their mode of association.

Journal of Experimental Biology, 14:43-59.

PDF typeset file: 109,620 bytes - 22 pages - no figures

In 1998, with genome projects routinely producing detailed genetics maps of mice and men and every other sort of organism, it can be difficult to imagine a time when there were no genetic maps. The idea that individual genes occupy regular positions on chromosomes was one of the great insights of early genetics, and the very first genetic map was published in 1913 by Alfred H. Sturtevant, who was working on fruit flies in the laboratory of Thomas H. Morgan at Columbia University.

Sturtevant is now well known as one of the most important early pioneers in genetic research. However, at the time he produced the first map, he was an undergraduate. Many years later, Sturtevant (A History of Genetics) described how an undergraduate came to be crucially involved in establishing the very foundations of classical genetics:

In 1909, the only time during his twenty-four years at Columbia, Morgan gave the opening lectures in the undergraduate course in beginning zoology. It so happened that C. B. Bridges and I were both in the class. While genetics was not mentioned, we were both attracted to Morgan and were fortunate enough, though both still undergraduates, to be given desks in his laboratory the following year (1910-1911). The possibilities of the genetic study of Drosophila were then just beginning to be apparent; we were at the right place at the right time. In the latter part of 1911, in conversation with Morgan, I suddenly realized that the variations in strength of linkage, already attributed by Morgan to differences in the spatial separation of the genes, offered the possibility of determining sequences in the linear dimension of a chromosome. I went home and spent most of the night (to the neglect of my undergraduate homework) in producing the first chromosome map, which included the sex-linked genes y, w, v, m, and r, in the order and approximately the relative spacing that they still appear on the standard maps (Sturtevant, 1913).

Sturtevant, Alfred H. — 1913.

The linear arrangement of six sex-linked factors in Drosophila, as shown by their mode of association.

Journal of Experimental Biology, 14:43-59.

PDF typeset file: 109,620 bytes - 22 pages - no figures

In 1998, with genome projects routinely producing detailed genetics maps of mice and men and every other sort of organism, it can be difficult to imagine a time when there were no genetic maps. The idea that individual genes occupy regular positions on chromosomes was one of the great insights of early genetics, and the very first genetic map was published in 1913 by Alfred H. Sturtevant, who was working on fruit flies in the laboratory of Thomas H. Morgan at Columbia University.

Sturtevant is now well known as one of the most important early pioneers in genetic research. However, at the time he produced the first map, he was an undergraduate. Many years later, Sturtevant (A History of Genetics) described how an undergraduate came to be crucially involved in establishing the very foundations of classical genetics:

In 1909, the only time during his twenty-four years at Columbia, Morgan gave the opening lectures in the undergraduate course in beginning zoology. It so happened that C. B. Bridges and I were both in the class. While genetics was not mentioned, we were both attracted to Morgan and were fortunate enough, though both still undergraduates, to be given desks in his laboratory the following year (1910-1911). The possibilities of the genetic study of Drosophila were then just beginning to be apparent; we were at the right place at the right time. In the latter part of 1911, in conversation with Morgan, I suddenly realized that the variations in strength of linkage, already attributed by Morgan to differences in the spatial separation of the genes, offered the possibility of determining sequences in the linear dimension of a chromosome. I went home and spent most of the night (to the neglect of my undergraduate homework) in producing the first chromosome map, which included the sex-linked genes y, w, v, m, and r, in the order and approximately the relative spacing that they still appear on the standard maps (Sturtevant, 1913).

Muller, Hermann J. — 1928.

The measurement of gene mutation rate in Drosophila, its high variability, and its dependence upon temperature.

Genetics, 13:279-357.

PDF image facsimile file: 79 pages

Schultz, Jack — 1929.

The minute reaction in the development of Drosophila melanogaster

Genetics, 14: 366-419.

PDF image facsimile file

McClintock, Barbara. — 1931.

The order of the genes C, Sh, and Wx in Zea mays with reference to a cytologically known point in the chromosome.

PNAS, 17:485-491.

PDF image facsimile file: 7 pages - several figures

In this paper, McClintock provides the basic genetic and cytological information necessary to understand the logic of her classic work with Harriet Creighton: A correlation of cytological and genetical crossing-over in Zea mays that appeared immediately following this paper in PNAS.

For additional commentary on Creighton and McClintock's important work, see Edward Coe and Lee B. Kass (2005) Proof of physical exchange of genes on the chromosomes. Proceedings of the National Academy of Sciences, USA. 102:6641-6646.

Morgan, Thomas H. — 1911.

The origin of five mutations in eye color in Drosophila and their modes of inheritance.

Science, New Series, 33:534-537.

PDF image facsimile file: 694,626 bytes - 4 pages - 0 figures

Morgan, Thomas H. — 1911.

The origin of nine wing mutations in Drosophila.

Science, New Series, 33:496-499.

PDF image facsimile file: 688,689 bytes - 4 pages - 0 figures

Muller, Hermann J. — 1925.

The regionally differential effect of X rays on crossing over in autosomes of Drosophila.

Genetics, 10:470-507.

PDF image facsimile file: 38 pages

Castle, W. E. — 1923.

The relation of Mendelism to mutation and evolution.

The American Naturalist, 57:559-561

PDF typeset file: 30,865 bytes - 5 pages - no figures

Here Castle offers a short note relating the behavior of simple Mendelian characters to the more complex, quantitative traits found in natural populations (and thus of interest to those studying evolution).

Thompson, David H. — 1931.

The side-chain theory of the structure of the Gene

Genetics, 16: 267-290.

PDF image facsimile file

Sturtevant, A. H., Bridges, C. B., and Morgan, T. H. — 1919.

The spatial relations of genes.

Proceedings of the National Academy of Sciences, 5:168-173.

PDF image facsimile file: 727,921 bytes - 6 pages

Muller, Hermann J., and Jacobs-Muller, Jessie M. — 1925.

The standard errors of chromosome distances and coincidence.

Genetics, 10:509-524.

PDF image facsimile file: 16 pages

Dobzhansky, t. — 1931.

Translocations Involving the Second and the fourth chromosomes of Drosophila melanogaster

Genetics, 16: 629-658.

PDF image facsimile file

Dobzhansky, T. — 1930.

Translocations involving the third and the fourth chromosomes of Drosophila melanogaster

Genetics, 15: 347-399.

PDF image facsimile file

Ibsen, Heman L. — 1916.

Tricolor Inheritance. I. the Tricolor Series in Guinea-pigs

Genetics, 1: 287-309.

PDF image facsimile file

Ibsen, Heman L. — 1916.

Tricolor Inheritance. II. the Basset Hound

Genetics, 1: 367-376.

PDF image facsimile file

Ibsen, Heman L. — 1916.

Tricolor Inheritance. III. Tortoiseshell Cats

Genetics, 1: 377-386.

PDF image facsimile file

Ibsen, Heman L. — 1919.

Tricolor Inheritance. Iv. the Triple Allelo-morphic Series in Guinea-pigs

Genetics, 4: 597-606.

PDF image facsimile file

Bridges, Calvin. — 1921.

Triploid intersexes in Drosophila melanogaster.

Science, 54:252-254.

PDF typeset file: 153,521 bytes - 5 pages - no figures

Work in the laboratory of T. H. Morgan was critical in establishing that genes are real, physical entities and that they are arranged in a linear order on chromosomes. Calvin Bridges was a key player in the Morgan group. In 1914, Bridges first demonstrated that a correlation existed between the incorrect assortment of X chromosomes and the incorrect assortment of some genes. In 1916, he expanded on that work to "prove" that sex-linked genes in Drosophila are carried on the X chromosome.

In this paper, Bridges shows that the correlation between mis-assortment of genes and chromosomes applies to the autosomes as well as to the sex chromosomes. In addition, he shows that sex determination in Drosophila appears to be driven by the ratio of X chromosomes to autosomes, not by the absolute number of X chromosomes.

Vries, Hugo de — 1918.

Twin hybrids of Oenothera hookeri T. and G..

Genetics, 3:397-421.

PDF image facsimile file: 25 pages

Waldeyer, W. — 1888.

Über Karyokinese und ihre Beziehungen zu den Befruchtungsvorgängen, I (On karyokinesis and its relation to the process of fertilization, I).

Archiv für mikroskopische Anatomie und Entwicklungsmechanik, 32:1-122.

PDF image facsimile file

In this review, Waldeyer summarizes the recent major advances in cytology that had occurred up to the date of his paper (1888). Then he proposes a new term — chromosome: Wir haben nun noch einige Punkte genauer zu besprechen, die bi den Vorschlag erlauben, diejenigen Dinge, welche soeben mit Boveri als "chromatische Elemente" bezeichnet wurden, an denen sieh einer der wichtigsten Akte der Karyokinese, die Flemming'sche Längstheilung vollzieht, mit einem besonderen terminus technicus "Chromosomen" zu belegen. Der Name "primäre Schleifen" passt nicht, da wir bei weitem nicht immer eine Schleifenform für diese Dinge haben. "Chromatische Elemente" ist zu lang. Andererseits sind sie so wichtig, dass ein besonderer küzerer Name wünschenswerth erscheint. Platner (160) gebraucht den Ausdruck "Karyosomen"; da dieser aber zu sehr an Kernkörperchen erinnert, dürfte eine andere Bezeichnung vorzuziehen sein. Ist die von mir vorgeschlagene praktisch verwendbar, so wird sie sich wohl einbürgern, sonst möge sie bald der Vergessenheit anheimfallen.

Weinberg, Wilhelm — 1908.

Über Vererbungsgesetze beim Menschen

Weinberg, Wilhelm 1908. Über Vererbungsgesetze beim Menschen. Zeitschrift für Induktive Abstammungs- und Vererbungslehre. 1:377-392.

Wilhelm Weinberg is the Weinberg of Hardy-Weinberg fame. Although Hardy’s contribution to population genetics was just a single-page letter to the editor of Science, Weinberg produced a more thorough treatment of the effects on allele frequencies of Mendelian mechanisms acting alone. We know that Weinberg was familiar with Hardy’s letter, since he (Weinberg) wrote a brief summary of Hardy’s paper for the Resultate (abstracts) section of this issue of this journal (p. 395). In that summary, Weinberg wrote:

Hardy, G. H. Mendelian Proportions in a mixed Population. Science N. S., 28 1908 S. 49. Yule hatte die Ansicht ausgesprochen, dass Brachydaktylie als dominierender Charakter mit der Zeit 3/4 der Bevoelkerung ausmachen muesse. (Die Anschauung von einer Zunahme der dominierenden Charaktere hat uebrigens auch Plate [Ludwig Plate of the Berlin Landwirthschaftliche Hochschul] vertreten.) Hardy weist nun darauf hin, dass Panmixie bei alternativer Vererbung zu stabiler Bevoelkerung fuehren muesse, was fuer einen speziellen Fall bereits 1904 Pearson und zu Anfang 1908 unabhaeng von ihm und in einfacherer Weise Referent nachgewiesen hat. Siehe auch diese Zeitschrift S. 377 ff.

S. 377 ff. Roughly translated as: Yule had argued that, over time, brachydactyly should come to dominate 3/4 of the population. (The idea of an increase in the dominating characters was also made by Plate.) Hardy now points out that panmixie (random mating) in alternative inheritance must lead to a stable population, which Pearson had also proven in 1904 for a special case and again, in 1908 (independently of Hardy), in an easier way. See also this magazine p. 377 ff.

Weinberg, Wilhelm — 1908.

Über Vererbungsgesetze beim Menschen.

Zeitschrift für Induktive Abstammungs- und Vererbungslehre, 1:377-392.

PDF image facsimile file

An early contribution from Weinberg on the study of inheritance in humans.

Muller, Hermann J. — 1922.

Variation due to change in the individual gene.

The American Naturalist, 56:32-50.

PDF typeset file: 69,751 bytes - 17 pages - no figures

This paper is from an address given by to the thirty-ninth annual meeting of the American Society of Naturalists, held in Toronto on 29 December 29 1921.

In this remarkably prescient analysis, Muller lays out the paradoxical nature of the genetic material. It is apparently both autocatalytic (i.e., directs its own synthesis) and heterocatalytic (i.e., directs the synthesis of other molecules), yet only the heterocatalytic function seems subject to mutation. With this, he defines the key problems that must be solved for a successful chemical model of the gene.

Muller also anticipated the ultimate development of molecular genetics:

That two distinct kinds of substances — the d'Hérelle substances (NOTE: viruses) and the genes — should both possess this most remarkable property of heritable variation or "mutability," each working by a totally different mechanism, is quite conceivable, considering the complexity of protoplasm, yet it would seem a curious coincidence indeed. It would open up the possibility of two totally different kinds of life, working by different mechanisms. On the other hand, if these d'Hérelle bodies were really genes, fundamentally like our chromosome genes, they would give us an utterly new angle from which to attack the gene problem. They are filterable, to some extent isolable, can be handled in test tubes, and their properties, as shown by their effects on the bacteria, can then be studied after treatment. It would be very rash to call these bodies genes, and yet at present we must confess that there is no distinction known between the genes and them. Hence we cannot categorically deny that perhaps we may be able to grind genes in a mortar and cook them in a beaker after all. Must we geneticists become bacteriologists, physiological chemists and physicists, simultaneously with being zoologists and botanists? Let us hope so.

Castle, W. E., and Wachter, W. L. — 1924.

Variations of Linkage in Rats and Mice

Genetics, 9: 1-12.

PDF image facsimile file

Anonymous. — 1844.

Vestiges of the Natural History of Creation.

London: John Churchill.

This is a full-text PDF image facsimile version of the entire 390-page original first edition.

In 1859, many had already begun to think deeply about the meaning and origin of creation. Fifteen years before the Origin, Vestiges of the Natural History of Creation appeared, published anonymously. In one sense, the book is hopelessly dated, and amateurish to boot. In another, the book is incredibly modern - an effort, in the author's own words, "to connect the natural sciences into a history of creation."

At one point, the author (revealed in the 12th edition to be Robert Chambers) uses the example of Charles Babbage's calculating engine (the first computer) to show how apparently miraculous changes might occur as the result of subtle changes in an underlying governing system.

NOTE: This is an electronic FACSIMILE of the original work. The PDF files contain images of the original pages. The files are large and will download slowly. It is probably best to download the files to disk for later viewing and printing. When printed, these files give output equivalent to good quality Xerox copies of the original.

Morgan, Thomas H. — 1909.

What are "factors" in Mendelian explanations?

American Breeders Association Reports, 5:365-369.

PDF typeset file: 108,227 bytes - 4 pages - no figures

Although T. H. Morgan is best known for heading the genetics laboratory at Columbia University (later at Cal Tech) that essentially defined American genetics research for decades, he was initially skeptical of the facile manner in which combinations of alleged Mendelian factors were being invoked to explain all manner of heritable traits.

This paper begins with a wonderful debunking of easy explanation:

In the modern interpretation of Mendelism, facts are being transformed into factors at a rapid rate. If one factor will not explain the facts, then two are invoked; if two prove insufficient, three will sometimes work out. The superior jugglery sometimes necessary to account for the result, may blind us, if taken too naïvely, to the common-place that the results are often so excellently "explained" because the explanation was invented to explain them. We work backwards from the facts to the factors, and then, presto! explain the facts by the very factors that we invented to account for them.

Demerec, Milislav — 1933.

What is a Gene?

Journal of Heredity, 24:368-378.

PDF typeset file: 679,936 bytes - 22 pages - several figures

Once the foundations of transmission genetics had been worked out, researchers began to consider what the chemical nature of the gene might be. Here Milislav Demerec offers one of the first such efforts. He concludes that the gene is a minute organic particle, capable of reproduction, located in a chromosome and responsible for the transmission of a hereditary characteristic. Moreover, he states that the available evidence suggests that genes are uni-molecular, and he notes:

If a gene is a complex organic molecule it would be expected to be similar in composition to other complex molecules, viz. molecular groups constituting this molecule (whatever these groups may be) would he arranged in chains and side chains. He then offers a drawing of the structure of DNA (!) as an example of a complex organic molecule, but is quick to add that The diagram is not intended to give any implication as to the number, the type, or the arrangement of the molecules in a gene group. Its purpose is to illustrate the molecular structure of a complex organic molecule.

Another 20 years would have to pass before the true chemical nature of the gene would be established.

Schultz, Jack — 1933.

X-ray Effects on Drosophila Pseudo-obscura

Genetics, 18: 284-291.

PDF image facsimile file

 

350 BC. — Aristotle.

On the Generation of Animals.

This is a full-text PDF version of the entire book.

Any collection of critical works in the history of biology must include works by Aristotle.

350 BC. — Aristotle.

On the Parts of Animals.

This is a full-text PDF version of the entire book.

Any collection of critical works in the history of biology must include works by Aristotle. Here, in On the Parts of Animals, Aristotle provides one of the world's first efforts to understand life in terms of its component parts.

350 BC. — Aristotle.

The History of Animals.

This is a full-text PDF version of the entire book.

Any collection of critical works in the history of biology must include works by Aristotle. Here, in The History of Animals, Aristotle provides a discussion of the diversity of life, with considerable attention to reproduction and heredity.

1798. — Malthus, T.

An Essay on the Principle of Population.

PDF typeset file: 948,754 bytes - 134 pages - no figures

In 1798, Thomas Malthus anonymously published this Essay, outlining why the forces of population growth tend to create a "struggle for existence" (see page 14). This book had a significant influence on Darwin as he looked for mechanisms that might explain evolutionary change. The influence shows, with Chapter Three of Darwin's Origin of Species entitled "Struggle for Existence". Now, 200 years after its first publication, Malthus' work is still an interesting read.

1844. — Anonymous.

Vestiges of the Natural History of Creation.

London: John Churchill.

This is a full-text PDF image facsimile version of the entire 390-page original first edition.

In 1859, many had already begun to think deeply about the meaning and origin of creation. Fifteen years before the Origin, Vestiges of the Natural History of Creation appeared, published anonymously. In one sense, the book is hopelessly dated, and amateurish to boot. In another, the book is incredibly modern - an effort, in the author's own words, "to connect the natural sciences into a history of creation."

At one point, the author (revealed in the 12th edition to be Robert Chambers) uses the example of Charles Babbage's calculating engine (the first computer) to show how apparently miraculous changes might occur as the result of subtle changes in an underlying governing system.

NOTE: This is an electronic FACSIMILE of the original work. The PDF files contain images of the original pages. The files are large and will download slowly. It is probably best to download the files to disk for later viewing and printing. When printed, these files give output equivalent to good quality Xerox copies of the original.

1845. — Darwin, C.

The Voyage of the Beagle, Second Edition.

London: John Murray.

This is a full-text, newly typeset, PDF version of the entire book.

For five years, from 1831-1836, Charles Darwin served as the official naturalist aboard the HMS Beagle as it visited exotic locations around the world. During this voyage, Darwin first came to wonder about the mechanisms driving the origin of species. This book chronicles the voyage and documents his early thinking.

1855. — Wallace. A. R.

On the law which has regulated the introduction of new species.

Annals and Magazine of Natural History, 2nd Series. 16:184-196.

PDF typeset file: 90,845 bytes - 17 pages - no figures

Today Darwin's name is known to everyone, while Alfred Russel Wallace is familiar to only a few. Yet the concept of evolution by natural selection was independently developed by Wallace and Darwin, with Wallace publishing first. This paper, and the 1858 manuscript he sent directly to Darwin, show clearly that, prior to Darwin's publication, Wallace had a firm grasp on the concept of evolution.

1859. — Darwin, C.

On the Origin of Species.

London: John Murray, Albemarle Street.

This is a full-text PDF image facsimile version of the entire 502-page original first edition.

This is the book that changed the world and defined modern biology. By making mechanisms of heritable variation central to the biggest issue in all of biology, Darwin initiated the genetics revolution.

1865. — Mendel, Gregor.

Experiments in plant hybridization.

Verhandlungen des naturforschenden Vereines in Brünn, Bd. IV für das Jahr 1865, Abhandlungen, 3-47.

PDF typeset file: 395,699 bytes - 41 pages - no figures

In February and March of 1865, Gregor Mendel presented the Brünn Natural History Society in Brünn, Czechoslovakia, with the results of his investigations into the mechanisms governing inheritance in pea plants. The next year, the work was published as Mendel, Gregor. 1866. "Versuche über Pflanzen Hybriden." Verhandlungen des naturforschenden Vereines in Brünn, 4:3-47.

In this remarkable paper, Mendel laid the groundwork for later became the science of genetics. However, the work was largely ignored when it appeared and Mendel moved on to other things. He died in 1884.

His work was rediscovered at the turn of the century and its significance immediately recognized. Genetics, as a formal scientific discipline, exploded into activity in 1900.

An annotated version of Mendel's paper is also available. The annotated version contains explanatory notes throughout the document. This can be useful to those reading Mendel's paper for the first time.

For those wishing to see and read Mendel in the original, a facsimile reprint edition is available. This version is in Adobe PDF format, but the pages are images of the original publication, not a new type-setting of the material.

You may also wish to visit The Mendel Web site, created by Roger Blumberg. The site offers many additional resources for the Mendel scholar.

1865. — Mendel, Gregor.

Experiments in plant hybridization. (annotated)

Verhandlungen des naturforschenden Vereines in Brünn, Bd. IV für das Jahr 1865, Abhandlungen, 3-47.

PDF typeset file: 395,699 bytes - 41 pages - no figures

In February and March of 1865, Gregor Mendel presented the Brünn Natural History Society in Brünn, Czechoslovakia, with the results of his investigations into the mechanisms governing inheritance in pea plants. The next year, the work was published as Mendel, Gregor. 1866. "Versuche über Pflanzen Hybriden." Verhandlungen des naturforschenden Vereines in Brünn, 4:3-47.

In this remarkable paper, Mendel laid the groundwork for later became the science of genetics. However, the work was largely ignored when it appeared and Mendel moved on to other things. He died in 1884.

His work was rediscovered at the turn of the century and its significance immediately recognized. Genetics, as a formal scientific discipline, exploded into activity in 1900.

A non-annotated version of Mendel's paper is also available.

For those wishing to see and read Mendel in the original, a facsimile reprint edition is available. This version is in Adobe PDF format, but the pages are images of the original publication, not a new type-setting of the material.

You may also wish to visit The Mendel Web site, created by Roger Blumberg. The site offers many additional resources for the Mendel scholar.

1865. — Mendel, Gregor.

Experiments in plant hybridization. (facsimile of first edition)

Verhandlungen des naturforschenden Vereines in Brünn, Bd. IV für das Jahr 1865, Abhandlungen, 3-47.

PDF image facsimile file: 2,142,414 bytes - 47 pages - no figures

For those wishing to see and read Mendel in the original, this provides an image facsimile of the original paper as it was published in German.

1866-1873. — Mendel, Gregor

Gregor Mendel's letters to Carl Nägeli, 1866-1873.

First published in English as: Mendel, G. 1950. Gregor Mendel's Letters to Carl Nägeli. Genetics, 35(5, pt 2): 1-29. Originally published as: Abhandlungen der Mathematisch-Physischen Klasse der Königlich Sächsischen Gesellschaft der Wissenschaften 29: 189-265, 1905. Reprinted in "Carl Correns, Gesammelte Abhandlungen zur Vererbungswissenschaft aus periodischen Schriften" 1899-1924. (Fritz V. Wettstein ed.) Berlin, Julius Springer, 1924. pp. 1237-1281.

PDF typeset file: 206,438 bytes - 36 pages - no figures

After his original paper on peas, Mendel published only one other paper on genetics, that one on Hieracium. These letters to Nägeli provide a rare additional glimpse into Mendel's thinking as he pursued his investigations on heredity.

1869. — Huxley, T. H.

Nature: Aphorisms by Goethe.

Nature, 1:9-11.

PDF image facsimile file: 343,040 bytes - 3 pages

A special article, written by Huxley on request for the first issue of Nature, a new publication. The article is mainly a lengthy quote from Goethe, consisting of an extended rhapsody on "Nature."

1869. — Mendel, Gregor

On Hieracium-hybrids obtained by artificial fertilisation.

Verhandlungen des naturforschenden Vereines, Abhandlungen, Brünn, Bd. VIII für das Jahr 1869, 26-31. (Translated and reprinted as an appendix to Bateson, W. 1909. Mendel's Principles of Heredity. Cambridge University Press.)

PDF typeset file: 57,344 bytes - 8 pages - no figures

After his original paper on peas, Mendel published only one other paper on genetics, this one on Hieracium. Unknown to Mendel, Hieracium does not experience normal sexual fertilization, making it impossible for him to confirm the findings that he had obtained earlier with peas.

1869. — Müller, F.

Facts and Arguments for Darwin.

London: John Murray, Albemarle Street

Johann Friedrich Theodor Müller (March 31, 1821 – May 21, 1897), always known as Fritz, was a German biologist and physician who emigrated to southern Brazil, where he lived in and near the German community of Blumenau, Santa Catarina. There he studied the natural history of the Atlantic forest south of São Paulo, and was an early advocate of Darwinism. He lived in Brazil for the rest of his life. Müllerian mimicry is named after him.

Müller became a strong supporter of Darwin. He wrote Für Darwin in 1864, arguing that Charles Darwin's theory of evolution by natural selection was correct, and that Brazilian crustaceans and their larvae could be affected by adaptations at any growth stage. This was translated into English by W.S. Dallas as Facts and Arguments for Darwin in 1869 (Darwin sponsored the translation and publication). If Müller had a weakness it was that his writing was much less readable than that of Darwin or Wallace; both the German and English editions are hard reading indeed, which has limited the appreciation of this significant book.

1883. — Brooks, W. K.

The Law of Heredity, Second Edition.

Baltimore and New York: John Murphy & Co., Publishers.

This is a full-text PDF image facsimile version of the entire 336-page original first edition.

It is often thought that, besides Mendel, little work on heredity occurred during the 19th Century. This is far from true. Darwin's Origin of Species placed the study of inherited variation at the center of biological thought. As this work by Brooks attests, considerable effort was made to understand heredity, especially as it related to natural selection.

Although the details of Brooks' analysis are now outdated, the book provides general insights into late-nineteenth Century thinking on heredity. Since Brooks was one of T. H. Morgan's instructors when Morgan was a student at Johns Hopkins, the book also provides insights into the specific instruction on heredity that was presented to the man who became the first recipient of a Nobel Prize for work on genetics.

NOTE: This is an electronic FACSIMILE of the original work. The PDF files contain images of the original pages. The files are large and will download slowly. It is probably best to download the files to disk for later viewing and printing. When printed, these files give output equivalent to good quality Xerox copies of the original.

1883. — Darwin, C.

The Variation of Animals and Plants Under Domestication, Second Edition, Revised (two volumes).

New York: D. Appleton & Co.

This is a full-text PDF image facsimile version of the entire 473-page volume I and the entire 495-page volume II of the original work.

Although Darwin's theories regarding the origin of species through natural selection required that some mechanism of heredity exist, no such mechanism was known when the Origin was written. After the Origin appeared, Darwin turned his attention to the mechanism(s) of heredity, resulting in his subsequent two-volume The Variation of Animals and Plants Under Domestication.

In volume I, Darwin summarized what was known about inheritance in a variety of domesticated species and concluded with a chapter, Inheritance, that begins his general summary of the mechanisms of inheritance. He continued this summary in volume II, which also offers Darwin's own theory of inheritance in Chapter XXVII, Provisional Hypothesis of Pangenesis.

The notion of pangenesis dominated late nineteenth-century thinking about inheritance. Although ultimately seen to be simply wrong, it was very influential and a familiarity with its tenets is essential for anyone wishing to understand the intellectual climate at the time Mendel was rediscovered in 1900.

NOTE: This is an electronic FACSIMILE of the original work. The PDF files contain images of the original pages. The files are large and will download slowly. It is probably best to download the files to disk for later viewing and printing. When printed, these files give output equivalent to good quality Xerox copies of the original.

1888. — Waldeyer, W.

Über Karyokinese und ihre Beziehungen zu den Befruchtungsvorgängen, I (On karyokinesis and its relation to the process of fertilization, I).

Archiv für mikroskopische Anatomie und Entwicklungsmechanik, 32:1-122.

PDF image facsimile file

In this review, Waldeyer summarizes the recent major advances in cytology that had occurred up to the date of his paper (1888). Then he proposes a new term — chromosome: Wir haben nun noch einige Punkte genauer zu besprechen, die bi den Vorschlag erlauben, diejenigen Dinge, welche soeben mit Boveri als "chromatische Elemente" bezeichnet wurden, an denen sieh einer der wichtigsten Akte der Karyokinese, die Flemming'sche Längstheilung vollzieht, mit einem besonderen terminus technicus "Chromosomen" zu belegen. Der Name "primäre Schleifen" passt nicht, da wir bei weitem nicht immer eine Schleifenform für diese Dinge haben. "Chromatische Elemente" ist zu lang. Andererseits sind sie so wichtig, dass ein besonderer küzerer Name wünschenswerth erscheint. Platner (160) gebraucht den Ausdruck "Karyosomen"; da dieser aber zu sehr an Kernkörperchen erinnert, dürfte eine andere Bezeichnung vorzuziehen sein. Ist die von mir vorgeschlagene praktisch verwendbar, so wird sie sich wohl einbürgern, sonst möge sie bald der Vergessenheit anheimfallen.

1889. — Galton, Francis

Natural Inheritance.

London: Macmillan

This is an image facsimile version of the entire 260-page original first edition.

1889. — Galton, Francis

Natural Inheritance.

London: Macmillan

This is an image facsimile version of the entire 260-page original first edition.

1889. — Weismann, August

Essays Upon Heredity.

Oxford at the Clarendon Press

This is a full-text PDF image facsimile version of the entire 700-plus pages of the original volumes.

August Weismann was one of the most influential biologists of the late nineteenth century. In Essays Upon Heredity he presents a series of essays giving his thoughts on the mechanisms of heredity. Two of the essays offer specific refutation of the idea that acquired characters can be inherited.

1893. — Weismann, August

The Germ-Plasm.

New York: Charles Scribner's Sons

This is a full-text PDF image facsimile version of the entire 477-page original book.

August Weismann was one of the most influential biologists of the late nineteenth century. In The Germ-Plasm he lays out a new theory of heredity, one based on the continuity of the germ-plasm (the gametes and the cells that give rise to the gametes) as opposed to the finite existence of the soma (the cells of the body).

Weismann introduces his book modestly:

Any attempt at the present time to work out a theory of heredity in detail may appear to many premature, and almost presumptuous: I confess there have been times when it has seemed so even to myself. I could not, however, resist the temptation to endeavour to penetrate the mystery of this most marvellous and complex chapter of life as far as my own ability and the present state of our knowledge permitted.

A key point in his theory is that it makes impossible the inheritance of acquired characteristics, and thus deals a death blow to Lamarckism, as well as to Darwin's pangenesis:

What first struck me when I began seriously to consider the problem of heredity, some ten years ago, was the necessity for assuming the existence of a special organised and living hereditary substance, which in all multicellular organisms, unlike the substance composing the perishable body of the individual, is transmitted from generation to generation. This is the theory of the continuity of the germ-plasm. My conclusions led me to doubt the usually accepted view of the transmission of variations acquired by the body (soma); and further research, combined with experiments, tended more and more to strengthen my conviction that in point of fact no such transmission occurs.

1894. — Bateson, William.

Materials for the Study of Variation.

London: Macmillan and Company.

This is a full-text PDF image facsimile version of the entire 598-page original first edition.

William Bateson was the first English-speaking scientist to recognize the significance of Mendel's work. Before the rediscovery of Mendel's work in 1900, Bateson had been active in studying morphology, with a special interest in discontinuous variation as it might apply to the origin of species.

In this book Bateson summarizes his observations on discontinuous variation. His concern for this kind of variation probably contributed greatly to the quickness with which he grasped the significance of Mendel's work.

NOTE: This is an electronic FACSIMILE of the original work. The PDF files contain images of the original pages. The files are large and will download slowly. It is probably best to download the files to disk for later viewing and printing. When printed, these files give output equivalent to good quality Xerox copies of the original.

1897. — Morgan, Thomas Hunt

The Development of the Frog's Egg: An Introduction to Experimental Embryology.

New York: The Macmillan Company

PDF image facsimile file: 46,153,994 bytes - 204 pages - several figures

Thomas Hunt Morgan is best known for his work in genetics, for which he received the Nobel Prize in 1933. Morgan's first research interest, however, was in embryology. This short book on frog development is his first book.

From the Preface: The development of the frog's egg was first made known through the studies of Swammerdam, Spallanzani, Rusconi, and von Baer. Their work laid the basis for all later research. More recently the experiments of Pfluger and of Roux on this egg have turned the attention of embryologists to the study of development from an experimental standpoint. Owing to the ease with which the frog's egg can be obtained, and its tenacity of life in a confined space, as well as its suitability for experimental work, it is an admirable subject with which to begin the study of vertebrate development. In the following pages an attempt is made to bring together the most important results of studies of the development of the frog's egg. I have attempted to give a continuous account of the development, as far as that is possible, from the time when the egg is forming to the moment when the young tadpole issues from the jelly-membranes. Especial weight has been laid on the results of experimental work, in the belief that the evidence from this source is the most instructive for an interpretation of the development. The evidence from the study of the normal development has, however, not been neglected, and wherever it has been possible I have attempted to combine the results of experiment and of observation, with the hope of more fully elucidating the changes that take place. Occasionally departures have been made from the immediate subject in hand in order to consider the results of other work having a close bearing on the problem under discussion. I have done this in the hope of pointing out more definite conclusions than could be drawn from the evidence of the frog's egg alone.

1898. — Galton, Francis.

A Diagram of Heredity.

Nature, 57:293.

PDF typeset file: 27,776 bytes - 5 pages - one figure

Some standard textbook descriptions of early genetics give the impression that, besides Mendel, no one attempted any genetic analysis in the entire nineteenth century. This is far from the truth, with Francis Galton offering a fine refutation. Starting just a few years after Mendel (and also working with peas), Galton carried out a series of well-received studies that resulted in his "Ancestral Law of Heredity," summarized diagrammatically in this brief communication. Galton's "Law" was so firmly established in some circles, that many adherents did not accept Mendelism until 1918, when R. A. Fisher showed that Galton's Law was in fact a natural consequence of Mendelian inheritance for polygenic traits.

1899. — Bateson, William.

Hybridisation and cross-breeding as a method of scientific investigation.

Journal of the Royal Horticultural Society, 24:59-66.

PDF typeset file: 89,523 bytes - 13 pages - no figures

In this talk, given in 1899, before Mendel's work had been rediscovered, Bateson gives his vision of what kind of research will be necessary to shed light on the processes of inheritance and evolution:

What we first require is to know what happens when a variety is crossed with its nearest allies. If the result is to have a scientific value, it is almost absolutely necessary that the offspring of such crossing should then be examined statistically. It must be recorded how many of the offspring resembled each parent and how many shewed characters intermediate between those of the parents. If the parents differ in several characters, the offspring must be examined statistically, and marshalled, as it is called, in respect of each of those characters separately.

One would be hard pressed to provide a better anticipation of the experimental approach of Gregor Mendel. Small wonder that Bateson, upon encountering Mendel's work, quickly became convinced that the correct method for studying inheritance was finally at hand.

1900. — Bateson, William.

Problems of heredity as a subject for horticultural investigation.

Journal of the Royal Horticultural Society, 25:54-61.

PDF typeset file: 84,218 bytes - 12 pages - no figures

Mendel's work of 1865 was largely neglected, until 1900 when it was simultaneously rediscovered by Hugo de Vries, Carl Correns, and Erik von Tschermak. When Mendel's work came to the attention of William Bateson (who himself had already been advocating controlled crosses as an approach to studying heredity), he was convinced that Mendel's work was of major importance:

That we are in the presence of a new principle of the highest importance is, I think, manifest. To what further conclusions it may lead us cannot yet be foretold.

Bateson devoted the remainder of his scientific career to further elucidations of "Mendelism." This present paper captures the enthusiasm of Bateson's first encounter with the works of Mendel.

1900. — Correns, Carl

G. Mendel's law concerning the behavior of progeny of varietal hybrids.

First published in English as: Correns, C., 1950. G. Mendel's law concerning the behavior of progeny of varietal hybrids. Genetics, 35(5, pt 2): 33-41. Originally published as: Correns, C. 1900. G. Mendels Regel über das Verhalten der Nachkommenschaft der Rassenbastarde. Berichte der Deutschen Botanischen Gesellschaft, 18: 158-168.

PDF typeset file: 78,900 bytes - 14 pages - no figures

Correns, along with Hugo de Vries and Erik von Tschermak, is considered to be one of the three co-discovers of Mendel's work in 1900. Correns was the only one of the three to acknowledge Mendel in the title of his paper. Correns' paper begins:

The latest publication of Hugo de Vries: Sur la loi de disjonction des hybrides, which through the courtesy of the author reached me yesterday, prompts me to make the following statement: In my hybridization experiments with varieties of maize and peas, I have come to the same results as de Vries, who experimented with varieties of many different kinds of plants, among them two varieties of maize. When I discovered the regularity of the phenomena, and the explanation thereof - to which I shall return presently - the same thing happened to me which now seems to be happening to de Vries: I thought that I had found something new. But then I convinced myself that the Abbot Gregor Mendel in Brünn, had, during the sixties, not only obtained the same result through extensive experiments with peas, which lasted for many years, as did de Vries and I, but had also given exactly the same explanation, as far as that was possible in 1866.

1900. — Tschermak, Erik von

Concerning artificial crossing in Pisum sativum

First published in English as: Tschermak, E. 1950. Concerning artificial crossing in Pisum sativum. Genetics, 35(5, pt 2): 42-47. Originally published as: Tschermak, E. 1900. Über Künstliche Kreuzung bei Pisum sativum. Berichte der Deutsche Botanischen Gesellschaft 18: 232-239, 1900.

PDF typeset file: 62,114 bytes - 10 pages - no figures

Tschermak, along with Carl Correns and Hugo de Vries, is considered to be one of the three co-discovers of Mendel's work in 1900. He had been working himself with garden peas when he rediscovered Mendel's prior contributions. In a postscript to his paper, he wrote:

Correns has just published experiments which also deal with artificial hybridization of different varieties of Pisum sativum and observations of the hybrids left to self-fertilization through several generations. They confirm, just as my own, Mendel's teachings. The simultaneous "discovery" of Mendel by Correns, de Vries, and myself appears to me especially gratifying. Even in the second year of experimentation, I too still believed that I had found something new.

1900. — Vries, Hugo de

Concerning the law of segregation of hybrids.

First published in English as: De Vries, H.. 1950. Concerning the law of segregation of hybrids. Genetics, 35(5, pt 2): 30-32. Originally published as: De Vries, H. 1900. Sur la loi de disjonction des hybrides. Comptes Rendus de l'Academie des Sciences (Paris), 130: 845-847.

PDF typeset file: 35,435 bytes - 6 pages - no figures

Hugo de Vries, along with Carl Correns and Erik von Tschermak, is considered to be one of the three co-discovers of Mendel's work in 1900. De Vries was by far the most established scientist at the time, with an established research record dealing with "mutations" (variations) and speciation.

In this first of two papers that he published in 1900, de Vries does not even mention Mendel by name, even though he adopts Mendelian terminology such as dominant and recessive.

1900. — Wilson, Edmund B.

The Cell in Development and Inheritance, 2nd Edition

New York: The Macmillan Company

This is a full-text PDF image facsimile version of the entire 490-page original book.

Edmund B. Wilson was the leading cytologist of his time and The Cell in Development and Inheritance was the definitive text on cytology from 1896 into the 1930's. A modern reader will be surprised to see how many of the illustrations in the book seem familiar – versions of many of them still appear in textbooks of introductory biology.

The last chapter in the book is entitled "Theories of Inheritance and Development:, and it begins:

Every discussion of inheritance and development must take as its point of departure the fact that the germ is a single cell similar in its essential nature to any one of the tissue-cells of which the body is composed. That a cell can carry with it the sum total of the heritage of the species, that it can in the course of a few days or weeks give rise to a mollusk or a man, is the greatest marvel of biological science. In attempting to analyze the problems that it involves, we must from the outset hold fast to the fact, on which Huxley insisted, that the wonderful formative energy of the germ is not impressed upon it from without, but is inherent in the egg as a heritage from the parental life of which it was originally a part. The development of the embryo is nothing new. It involves no breach of continuity, and is but a continuation of the vital processes going on in the parental body. What gives development its marvelous character is the rapidity with which it proceeds and the diversity of the results attained in a span so brief.

But when we have grasped this cardinal fact, we have but focussed our instruments for a study of the real problem. How do the adult characteristics lie latent in the germ-cell; and how do they become patent as development proceeds? This is the final question that looms in the background of every investigation of the cell. In approaching it we may well make a frank confession of ignorance; for in spite of all that the microscope has revealed, we have not yet penetrated the mystery, and inheritance and development still remain in their fundamental aspects as great a riddle as they were to the Greeks. What we have gained is a tolerably precise acquaintance with the external aspects of development. The gross errors of the early preformationists have been dispelled.' We know that the germ-cell contains no predelineated embryo; that development is manifested, on the one hand, by the cleavage of the egg, on the other hand, by a process of differentiation, through which the products of cleavage gradually assume diverse forms and functions, and so accomplish a physiological division of labour. We can clearly recognize the fact that these processes fall in the same category as those that take place in the tissue-cells; for the cleavage of the ovum is a form of mitotic cell-division, while, as many eminent naturalists have perceived, differentiation is nearly related to growth and has its root in the phenomena of nutrition and metabolism. The real problem of development is the orderly sequence and correlation of these phenomena toward a typical result. We cannot escape the conclusion that this is the outcome of the organization of the germ-cells; but the nature of that which, for lack of a better term, we call "organization," is and doubtless long will remain almost wholly in the dark.

1901. — McClung, C. E.

Notes on the accessory chromosome.

Anatomischer Anzeiger, 20:220-226.

PDF typeset file: 58,569 bytes - 12 pages - no figures

In this brief paper, McClung introduces the evidence that male and female insects exhibit different chromosomal structures in their nuclei and that spermatozoa fall into two types - those that carry the "accessory chromosome" and those that do not.

Based on this analysis, McClung suggests that the presence or absence of the "accessory chromosome" in spermatozoa may determine the sex of the progeny. McClung published this short note in 1901 to alert the scientific community of his findings and to alert them to a more detailed argument that he had already submitted for publication elsewhere and that he knew would appear a year later, in McClung, C. E. 1902. The accessory chromosome - Sex determinant? Biological Bulletin, 3:43-84.

1902. — Bateson, William, and Saunders, E. R.

The facts of heredity in the light of Mendel's discovery.

Reports to the Evolution Committee of the Royal Society, I, 1902, pp. 125-160

PDF typeset file: 543,744 bytes - 41 pages - no figures

William Bateson was the first English-speaking scientist to appreciate the potential significance of Mendel's work. He began working immediately to confirm and extend Mendel's findings. This report to the evolution committee of the Royal Society represents one of the very first systematic investigations into Mendelism as a possible general explanation for the fundamental mechanisms of heredity.

1902. — Bateson, William.

Application for Support of an Experimental Investigation of Mendel's Principles of Heredity in Animals and Plants.

In Bateson, B. 1928. William Bateson, F.R.S.: His Essays & Addresses, together with a Short Account of his Life. Cambridge: Cambridge University Press.

PDF typeset file: 36,348 bytes - 6 pages - no figures

Although not considered to be one of the "official" rediscovers of Mendel's work, William Bateson was the first English-speaking scientist to recognize the importance of Mendel's work and he immediately set out to bring Mendel's work to the attention of the scientific community. Bateson coined the word "genetics" to name the new field and made many important contributions to its development.

This present document is a copy of a letter that Bateson wrote in 1902, seeking financial support from the Trustees of the Carnegie Institution for continued investigations into Mendelian mechanisms of inheritance.

The letter was almost certainly the world's first grant application in the new field of genetics. It was declined.

1902. — Bateson, William.

Mendel's Principles of Heredity: A Defence.

London: Cambridge University Press.

This is a full-text PDF image facsimile version of the entire 212-page original first edition.

William Bateson was the first English-speaking scientist to recognize the significance of Mendel's work. In an 1899 paper, he had anticipated the sort of experimental design that Mendel used, and in 1900, shortly after Mendel's rediscovery, he published another paper in which he summarized Mendel's work in English, declaring it to be "a new principle of the highest importance."

In the present work, Bateson offers a book-length presentation of Mendel's approach to genetic research, including the first English translation of both Mendel's work on peas and his later work on Hieracium. The book is subtitled A Defence because the Mendelian approach to genetics was initially strongly resisted by the biometrician school, which based their thinking on Galton's ancestral law of heredity.

NOTE: This is an electronic FACSIMILE of the original work. The PDF files contain images of the original pages. The files are large and will download slowly. It is probably best to download the files to disk for later viewing and printing. When printed, these files give output equivalent to good quality Xerox copies of the original.

1902. — Cannon, W. A.

A cytological basis for the Mendelian laws.

Bulletin of the Torrey Botanical Club, 29:657-661.

PDF typeset file: 191,965 bytes - 6 pages

1902. — Garrod, Archibald E.

The incidence of alkaptonuria: A study in chemical individuality.

Lancet, ii:1616-1620.

PDF typeset file: 145,052 bytes - 18 pages - no figures

This paper is a true classic. Like Mendel's own work, this report offers insights so far ahead of its time that it, and Garrod's follow-on work, were largely neglected, until later efforts to elucidate the physiological functioning of genes led to the Nobel-prize-winning one-gene, one-enzyme hypothesis.

Less than two years after the rediscovery of Mendelism and just a few years after the word biochemistry was first coined, Garrod reports on alkaptonuria in humans and comes to the conclusion that it is inherited as a Mendelian recessive and that the occurrence of mutations (sports in the word of the time) in metabolic function should be no more surprising than inherited variations in morphology.

1902. — McClung, C. E.

The accessory chromosome - Sex determinant?

Biological Bulletin, 3:43-84.

PDF typeset file: 188,601 bytes - 40 pages - no figures

In this paper, McClung analyzes the evidence that male and female insects exhibit different chromosomal structures in their nuclei and that spermatozoa fall into two types - those that carry the "accessory chromosome" and those that do not.

Based on this analysis, McClung offers the bold hypothesis that the presence or absence of the "accessory chromosome" in spermatozoa may determine the sex of the progeny:

A most significant fact ... is that the [accessory chromosome] is apportioned to but one half of the spermatozoa. Assuming it to be true that the chromatin is the important part of the cell in the matter of heredity, then it follows that we have two kinds of spermatozoa that differ from each other in a vital matter. We expect, therefore, to find in the offspring two sorts of individuals in approximately equal numbers. ... [Since] nothing but sexual characters ... divides the members of a species into two well-defined groups, ... we are logically forced to the conclusion that the [accessory] chromosome has some bearing upon this arrangement.

That is, McClung hypothesizes that a difference in chromosome number is the cause, not an effect, of sex determination. This paper represents the first effort to associate the determination of a particular trait with a particular chromosome.

1902. — Sutton, Walter S.

On the morphology of the chromosome group in Brachystola magna.

Biological Bulletin, 4:24-39.

PDF typeset file: 119,906 bytes - 18 pages - 11 figures

In this paper, Sutton reports cytological studies of grasshopper chromosomes that lead him to conclude that (a) chromosomes have individuality, (b) that they occur in pairs, with one member of each pair contributed by each parent, and (c) that the paired chromosomes separate from each other during meiosis.

After presenting considerable evidence for his assertions, Sutton closes his paper with a sly reference to its undoubted significance:

I may finally call attention to the probability that the association of paternal and maternal chromosomes in pairs and their subsequent separation during the reducing division as indicated above may constitute the physical basis of the Mendelian law of heredity. To this subject I hope soon to return in another place.

1902. — Weldon, W. F. R.

Mendel's laws of alternative inheritance in peas.

Biometrika, 1:228-254.

PDF typeset file: 1,430,843 bytes - 33 pages - several figures

Textbook treatments of genetics often give the impression that upon being rediscovered Mendel's dominated the field. This is not so. Galton and his followers had been working for decades studying patterns of inheritance and had developed a formal quantitative model for the inheritance of "natural" (i.e., continuous) traits.

The biometricians, as they were called, felt that Mendel's work was a special case, valid only when applied to discontinuous traits in domesticated species. Weldon was a leading proponent of the biometrician school. This paper provides a strong summary of why the biometricians believed Mendel's work to be fundamentally flawed and of no general consequence. The paper concludes:

The fundamental mistake which vitiates all work based upon Mendel's method is the neglect of ancestry, and the attempt to regard the whole effect upon offspring, produced by a particular parent, as due to the existence in the parent of particular structural characters; while the contradictory results obtained by those who have observed the offspring of parents apparently identical in certain characters show clearly enough that not only the parents themselves, but their race, that is their ancestry, must be taken into account before the result of pairing them can be predicted.

1902. — Wilson, Edmund B.

Mendel's principles of heredity and the maturation of the germ cells.

Science, NS 16: 991-993.

PDF typeset file: 40,134 bytes - 5 pages - no figures

In this short note, E. B. Wilson calls attention to the possible relationship between Mendelian patterns of inheritance and the assortment of chromosomes in meiosis.

1902. — Yule, G. Udny

Mendel's laws and their probably relations to intra-racial heredity.

The New Phytologist, 1:193-207,222-238.

PDF image facsimile file: 32 pages

1903. — Sutton, Walter S.

The chromosomes in heredity.

Biological Bulletin, 4: 231-251.

PDF typeset file: 133,686 bytes - 20 pages - no figures

Early on, some researchers noticed that Mendel's theory required that some kind of hereditary unit segregate in pairs to offspring. Sutton was one of the first to note that the chromosomes behaved in exactly a manner to match this requirement.

The opening lines of his paper show that he is aware of the significance of his observations:

In a recent announcement of some results of a critical study of the chromosomes in the various cell generations of Brachystola the author briefly called attention to a possible relation between the phenomena there described and certain conclusions first drawn from observations on plant hybrids by Gregor Mendel in 1865, and recently confirmed by a number of able investigators. Further attention has already been called to the theoretical aspects of the subject in a brief communication by Professor E. B. Wilson. The present paper is devoted to a more detailed discussion of these aspects, the speculative character of which may be justified by the attempt to indicate certain lines of work calculated to test the validity of the conclusions drawn. The general conceptions here advanced were evolved purely from cytological data, before the author had knowledge of the Mendelian principles, and are now presented as the contribution of a cytologist who can make no pretensions to complete familiarity with the results of experimental studies on heredity. As will appear hereafter, they completely satisfy the conditions in typical Mendelian cases, and it seems that many of the known deviations from the Mendelian type may be explained by easily conceivable variations from the normal chromosomic processes.

1904. — Bateson, William, Saunders, E. R., and Punnett, R. C.

Experimental Studies in the Physiology of Heredity.

Reports to the Evolution Committee of the Royal Society, II, 1904, pp. 1-131

PDF image facsimile file: 6,907,359 bytes - 154 pages - no figures

William Bateson was the first English-speaking scientist to appreciate the potential significance of Mendel's work. He and his co-workers began immediately to confirm and extend Mendel's findings. This report to the evolution committee of the Royal Society represents one of the very first systematic investigations into Mendelism as a possible general explanation for the fundamental mechanisms of heredity.

1904. — Hurst, C. C.

Experiments with Poultry.

Reports to the Evolution Committee of the Royal Society, II, 1904, pp. 131-154

PDF image facsimile file: 6,907,359 bytes - 154 pages - no figures

William Bateson was the first English-speaking scientist to appreciate the potential significance of Mendel's work. He and his co-workers began immediately to confirm and extend Mendel's findings. C. C. Hurst was one of Wm Bateson's early co-workers. This report to the evolution committee of the Royal Society represents one of the very first systematic investigations into Mendelism as a possible general explanation for the fundamental mechanisms of heredity.

1905. — Darbishire, A. D.

On the supposed antagonism of Mendelian to biometric theories of heredity.

Manchester Memoirs, 49:1-19.

PDF typeset file: 16 pages

1905. — Punnett, R. C.

Mendelism, 1st Edition.

Cambridge: Bowes and Bowes

PDF image facsimile file: 1,382,040 bytes - 71 pages - several figures

This little book is the first edition of the first genetics textbook ever written. It was published just five years after Mendel's work was rediscovered.

1905. — Stevens, Nettie M.

Studies in Spermatogenesis with especial reference to the "accessory chromosome".

Carnegie Institution of Washington, Publication No. 36., pp 1-33.

PDF image facsimile file: 1,448,192 bytes - 33 pages - 7 plates

1905. — Wilson, Edmund B.

The chromosomes in relation to the determination of sex in insects.

Science, N.S. 22:500-502.

PDF typeset file: 43,282 bytes - 8 pages - no figures

In this short note, Wilson (a leading cell biologist of his time) offers his endorsement of the idea that there is a relationship between specific chromosomes and the determination of sex in insects:

Material procured during the past summer demonstrates with great clearness that the sexes of Hemiptera show constant and characteristic differences in the chromosome groups, which are of such a nature as to leave no doubt that a definite connection of some kind between the chromosomes and the determination of sex exists in these animals. These differences are of two types. In one of these, the cells of the female possess one more chromosome than those of the male; in the other, both sexes possess the same number of chromosomes, but one of the chromosomes in the male is much smaller than the corresponding one in the female (which is in agreement with the observations of Stevens on the beetle Tenebrio).

Wilson's contribution is the observation that the various cases all seem to fall cleanly into one of two types — those in which the male seems to be missing a chromosome, and those in which the male is carrying a pair of mis-matched chromosomes. Wilson's goes on to note that he does not believe that the 'accessory chromosomes' are actual sex determinants as conjectured by McClung, but rather that they probably act in a quantitative, not qualitative manner.

Wilson's endorsement of the idea that chromosome make-up is related to sex determination greatly facilitated the later general acceptance of the notion that individual chromosomes might be related to individual traits. Of course, sex is not a simple Mendelian trait, such as round or wrinkled peas, but nonetheless the evidence that some aspect of phenotype (sex) was related to some aspect of genotype was an important initial step in bringing genetics together with cytology.

1906. — Stevens, Nettie M.

Studies in Spermatogenesis Part II., A comparative study of the heterochromosomes in certain species of coleoptera, hemiptera and lepidoptera, with especial reference to sex determination.

Carnegie Institution of Washington, Publication No. 36, part II., pp 1-43.

PDF image facsimile file: 1,936,652 bytes - 43 pages - 8 plates

1906. — Stevens, Nettie M.

Studies on the germ cells of aphids.

Carnegie Institution of Washington, Publication No. 51., pp 1-28.

PDF image facsimile file: 1,180,954 bytes - 28 pages - 4 plates

1907. — Punnett, R. C.

Mendelism, 2nd Edition.

Cambridge: Bowes and Bowes

PDF image facsimile file: 1,832,735 bytes - 93 pages - several figures

This second edition of Punnett's text on Mendelism came out just two years after the first edition. In this new edition, Punnett Squares appeared for the first time. Also, the author included an index (that could fit on a single page with room left over).

1908. — Bateson, William.

The Methods and Scope of Genetics.

London: Cambridge University Press.

This is a newly typeset full-text version of the entire 49-page original first edition.

This short book is a copy of the Inaugural Address, given by Bateson upon the creation of the Professorship of Biology at Cambridge. In his introduction, Bateson notes:

The Professorship of Biology was founded in 1908 for a period of five years partly by the generosity of an anonymous benefactor, and partly by the University of Cambridge. The object of the endowment was the promotion of inquiries into the physiology of Heredity and Variation, a study now spoken of as Genetics.

It is now recognized that the progress of such inquiries will chiefly be accomplished by the application of experimental methods, especially those which Mendel's discovery has suggested. The purpose of this inaugural lecture is to describe the outlook over this field of research in a manner intelligible to students of other parts of knowledge.

Here then is a view of how one of the very first practitioners of genetics conceived of the "Methods and Scope of Genetics".

1908. — Gager, Charles Stuart

Some Physiological Effects of Radium Rays

The American Naturalist 42: 761-778.

1908. — Hardy, G. H.

Mendelian Proportions in a Mixed Population.

Science, NS. XXVIII:49-50.

PDF typeset file: 19,473 bytes - 1 page - no figures

Every geneticist has heard of the Hardy-Weinberg Law and of Hardy-Weinberg Equilibrium, and nearly all basic biology texts teach that G. H. Hardy played a seminal role in founding population genetics. But, what most biologists don't realize is that Hardy's total contribution to biology consisted of a single letter to the editor in Science. The letter began,

I am reluctant to intrude in a discussion concerning matters of which I have no expert knowledge, and I should have expected the very simple point which I wish to make to have been familiar to biologists. However, some remarks of Mr. Udny Yule, to which Mr. R. C. Punnett has called my attention, suggest that it may still be worth making.

With that, Hardy offered his "simple point" and then washed his hands of biology. His autobiography, A Mathematician's Apology, makes no mention of population genetics.

1908. — Spillman, W. J.

Spurious Allelomorphism: Results of Some Recent Investigations

The American Naturalist

1908. — Thomson, J. Arthur.

Heredity.

London: John Murray

This is a PDF image facsimile version of the entire 596-page original first edition.

This book is one of the first textbook treatments of heredity after the rediscovery of Mendel's work. Thomson provides his analysis in the context of the understanding of inheritance in the pre-Mendelian late nineteenth century. Chapter 11, History of Theories of Heredity and Inheritance summarizes many of the nineteenth-century theories of heredity.

In his bibliography, Thomson cites many nineteenth-century works. He also provides a subject-index to the bibliography, making this collection of citations especially valuable.

1908. — Weinberg, Wilhelm

Über Vererbungsgesetze beim Menschen

Weinberg, Wilhelm 1908. Über Vererbungsgesetze beim Menschen. Zeitschrift für Induktive Abstammungs- und Vererbungslehre. 1:440-460.

1908. — Weinberg, Wilhelm

Über Vererbungsgesetze beim Menschen

Weinberg, Wilhelm 1908. Über Vererbungsgesetze beim Menschen. Zeitschrift für Induktive Abstammungs- und Vererbungslehre. 1:377-392.

Wilhelm Weinberg is the Weinberg of Hardy-Weinberg fame. Although Hardy’s contribution to population genetics was just a single-page letter to the editor of Science, Weinberg produced a more thorough treatment of the effects on allele frequencies of Mendelian mechanisms acting alone. We know that Weinberg was familiar with Hardy’s letter, since he (Weinberg) wrote a brief summary of Hardy’s paper for the Resultate (abstracts) section of this issue of this journal (p. 395). In that summary, Weinberg wrote:

Hardy, G. H. Mendelian Proportions in a mixed Population. Science N. S., 28 1908 S. 49. Yule hatte die Ansicht ausgesprochen, dass Brachydaktylie als dominierender Charakter mit der Zeit 3/4 der Bevoelkerung ausmachen muesse. (Die Anschauung von einer Zunahme der dominierenden Charaktere hat uebrigens auch Plate [Ludwig Plate of the Berlin Landwirthschaftliche Hochschul] vertreten.) Hardy weist nun darauf hin, dass Panmixie bei alternativer Vererbung zu stabiler Bevoelkerung fuehren muesse, was fuer einen speziellen Fall bereits 1904 Pearson und zu Anfang 1908 unabhaeng von ihm und in einfacherer Weise Referent nachgewiesen hat. Siehe auch diese Zeitschrift S. 377 ff.

S. 377 ff. Roughly translated as: Yule had argued that, over time, brachydactyly should come to dominate 3/4 of the population. (The idea of an increase in the dominating characters was also made by Plate.) Hardy now points out that panmixie (random mating) in alternative inheritance must lead to a stable population, which Pearson had also proven in 1904 for a special case and again, in 1908 (independently of Hardy), in an easier way. See also this magazine p. 377 ff.

1908. — Weinberg, Wilhelm

Über Vererbungsgesetze beim Menschen.

Zeitschrift für Induktive Abstammungs- und Vererbungslehre, 1:377-392.

PDF image facsimile file

An early contribution from Weinberg on the study of inheritance in humans.

1908. — Woods, F. A.

Recent Studies in Human Heredity

The American Naturalist 42: 685-693.

1909. — Cook, O. F.

Pure Strains as Artifacts of Breeding

The American Naturalist 43: 241-242.

1909. — Cox, Charles F.

Charles Darwin and the Mutation Theory

The American Naturalist 43: 65-91.

1909. — Davenport, Gertrude C, and Davenport, Charles B.

Heredity of Hair Color in Man

The American Naturalist 43: 193-211.

1909. — Davis, Bradley M.

The Permanence of Chromosomes in Plant Cells

The American Naturalist

1909. — East, Edward M.

The Distinction between Development and Heredity in Inbreeding.

The American Naturalist 43: 173-181.

1909. — Morgan, Thomas H.

Are the Drone Eggs of the Honey-Bee Fertilized?

The American Naturalist 43: 316-317.

1909. — Morgan, Thomas H.

Breeding Experiments with Rats

The American Naturalist 43: 182-185.

1909. — Morgan, Thomas H.

Hybridology and Gynandromorphism

The American Naturalist

1909. — Morgan, Thomas H.

Recent Experiments on the Inheritance of Coat Colors in Mice

The American Naturalist 43: 494-510.

1909. — Morgan, Thomas H.

What are "factors" in Mendelian explanations?

American Breeders Association Reports, 5:365-369.

PDF typeset file: 108,227 bytes - 4 pages - no figures

Although T. H. Morgan is best known for heading the genetics laboratory at Columbia University (later at Cal Tech) that essentially defined American genetics research for decades, he was initially skeptical of the facile manner in which combinations of alleged Mendelian factors were being invoked to explain all manner of heritable traits.

This paper begins with a wonderful debunking of easy explanation:

In the modern interpretation of Mendelism, facts are being transformed into factors at a rapid rate. If one factor will not explain the facts, then two are invoked; if two prove insufficient, three will sometimes work out. The superior jugglery sometimes necessary to account for the result, may blind us, if taken too naïvely, to the common-place that the results are often so excellently "explained" because the explanation was invented to explain them. We work backwards from the facts to the factors, and then, presto! explain the facts by the very factors that we invented to account for them.

1909. — Powers, J. H.

Are Species Realities or Concepts Only?

The American Naturalist

1909. — Shull, George Harrison

The "Presence and Absence" Hypothesis.

The American Naturalist, 43:410-419.

PDF image facsimile file: 655,705 bytes - 10 pages - 0 figures

1909. — Spillman, W. J.

A Case of Non-Mendelian Heredity

The American Naturalist 43: 437-448.

1909. — Spillman, W. J.

The Nature of "Unit" Characters

The American Naturalist 43: 243-248.

1909. — Wilson, Edmund B.

Recent researches on the determination and heredity of sex.

Science, NS 29:53-70.

PDF image facsimile file: 18 pages

1909. — Wilson, Edmund B.

Secondary chromosome-couplings and the sexual relations in Abraxas.

Science, NS 29:704-706.

PDF image facsimile file: 3 pages

1910. — Castle, W. E., and Little, C. C.

On a modified Mendelian ratio among yellow mice.

Science, N.S., 32:868-870.

PDF typeset file: 39,133 bytes - 7 pages - no figures

Here, Castle and Little offer evidence consistent with the idea that the gene for yellow fur in mice, studied earlier by Cuénot, is probably lethal when carried homozygously.

1910. — Drinkwater, H.

A Lecture on Mendelism.

London: J. M. Dent & Sons.

This is an image facsimile version of the entire 48-page original first edition.

This short book was based on a lecture given by Drinkwater as one of a series known as "Science Lectures for the People." The book provides insights into the general perception (as opposed to scholarly view) of genetics very early after the field had begun.

The book also contains some nice portraits of Mendel, Bateson, and Punnett.

1910. — Montgomery, Thos. H., Jr.

ARE PARTICULAR CHROMOSOMES SEX DETERMINANTS?

Biological Bulletin, 19:1-17.

PDF image facsimile file

1910. — Morgan, Thomas H.

Chromosomes and Heredity.

The American Naturalist, 44:449-496.

PDF typeset file: 222,436 bytes - 38 pages - one figure

Work in the laboratory of T. H. Morgan was critical in establishing that genes are real, physical entities and that they are arranged in a linear order on chromosomes. In this early, analytical paper, Morgan considers whether or not chromosomes might be carriers of the hereditary material and whether or not they might control sex determination.

Morgan's careful and logical approach is captured in his final comments on sex determination:

Science advances by carefully weighing all of the evidence at her command. When a decision is not warranted by the facts, experience teaches that it is wise to suspend judgment, until the evidence can be put to further test. This is the position we are in today concerning the interpretation of the mechanism that we have found by means of which sex is determined. I could, by ignoring the difficulties and by emphasizing the important discoveries that have been made, have implied that the problem of sex determination has been solved. I have tried rather to weigh the evidence, as it stands, in the spirit of the judge rather than in that of the advocate. One point at least I hope to have made evident, that we have discovered in the microscopic study of the germ cells a mechanism that is connected in some way with sex determination; and I have tried to show, also, that this mechanism accords precisely with that the experimental results seem to call for. The old view that sex is determined by external conditions is entirely disproven, and we have discovered an internal mechanism by means of which the equality of the sexes where equality exists is attained. We see how the results are automatically reached even if we can not entirely understand the details of the process. These discoveries mark a distinct advance in our study of this difficult problem.

1910. — Morgan, Thomas H.

Chromosomes and heredity.

The American Naturalist, 44: 449-496.

PDF typeset file: 284,612 bytes - 38 pages - no figures

Between 1910 and 1915, work in Morgan's lab laid the foundation of the modern chromosomal theory of heredity. This paper represents Morgan's thinking early in this process.

The opening lines of his paper captures the issues that he then deemed important to a consideration of the mechanism of heredity:

We have come to look upon the problem of heredity as identical with the problem of development. The word heredity stands for those properties of the germ-cells that find their expression in the developing and developed organism. When we speak of the transmission of characters from parent to offspring, we are speaking metaphorically; for we now realize that it is not characters that are transmitted to the child from the body of the parent, but that the parent carries over the material common to both parent and offspring. This point of view is so generally accepted to-day that I hesitate to restate it. It will serve at least to show that in what I am about to say regarding heredity and the germ-cells I shall ignore entirely the possibility that characters first acquired by the body are transmitted to the germ. Were there sufficient evidence to establish this view, our problem would be affected in so far as that we should not only have to account for the way in which the fertilized egg produces the characters of the adult, but also for the way in which the characters of the adult modify the germ-cells. The modern literature of development and heredity is permeated through and through by two contending or contrasting views as to how the germ produces the characters of the individual. One school looks upon the egg and sperm as containing samples or particles of all the characters of the species, race, line, or even of the individual. This view I shall speak of as the particulate theory of development. The other school interprets the egg or sperm as a kind of material capable of progressing in definite ways as it passes through a series of stages that we call its development. I shall call this view the theory of physico-chemical reaction, or briefly the reaction theory.

1910. — Morgan, Thomas H.

Sex-limited inheritance in Drosophila.

Science, 32:120-122.

PDF typeset file: 72,823 bytes - 14 pages - no figures

After Mendel's work was rediscovered in 1900, many researchers worked to confirm and extend his findings. Although a possible relationship between genes and chromosomes was suggested almost immediately, proof of that relationship, or even evidence that genes were physical objects, remained elusive. To many, the gene served only as a theoretical construct, conveniently invoked to explain observed inheritance patterns. In 1909, Morgan himself published a paper in which he expressed his skepticism about the facility with which Mendelian explanations were adjusted to fit the facts.

Just one year later, however, Morgan published the results of his work on an atypical male fruit fly that appeared in his laboratory, and all this began to change. Normally Drosophila melanogaster have red eyes, but Morgan's new fly had white eyes. The inheritance pattern for this new eye-color trait suggested strongly that the gene for eye-color was physically attached to the X-chromosome. In the paper, Morgan concluded:

It now becomes evident why we found it necessary to assume a coupling of [the eye-color gene] and X in one of the spermatozoa of the red-eyed F1 hybrid. The fact is that this R and X are combined, and have never existed apart.

In this present paper, Morgan offered the first evidence that genes are real, physical objects, located on chromosomes, with properties that could be manipulated and studied experimentally. The white-eyed fly provided the foundation upon which Morgan and his students established the modern theory of the gene.

1910. — Vries, Hugo de.

Intracellular Pangenesis.

Chicago: The Open Court Publishing Co.

This is a full-text PDF image facsimile version of the entire 270-page original book

This classic work, first published in German in 1889, presents De Vries's theory of the pangen, a morphological structure carrying hereditary material. The name "gene," later coined by Johannsen, was derived from de Vries's pangen.

Hugo De Vries is often now remembered, along with Correns and von Tschermak, primarily for their role in the rediscovery of Mendel in 1900. Of the three, however, De Vries was by far the most established scientist. He was one of the most well-known botanists in Europe and had already been developing his own theoretical model of heredity - intracellular pangenesis.

Intracellular pangenesis was based on Darwins's concept of pangenesis as presented in chapter 27 of his massive, two-volume The Variation of Animals and Plants under Domestication. De Vries view, however, has a more modern feel than Darwin's, as De Vries thought about the inheritance of individual characters (as did Mendel), not just about more general overall species characteristics. De Vries called his units of inheritance pangens and later he came to believe that a pangen for a particular trait was the same, no matter in which species it occurred. This is an interesting anticipation of what would later be seen as genetic homology.

1911. — Castle, W. E.

Heredity in Relation to Evolution and Animal Breeding.

New York: D. Appleton and Company

This is an image facsimile version of the entire 184-page original edition.

1911. — Doncaster, L.

Heredity in the Light of Recent Research.

Cambridge: University Press

This is an image facsimile version of the entire 144-page original first edition.

1911. — Morgan, Thomas H.

Chromosomes and associative inheritance.

Science, New Series, 34:636-638.

PDF image facsimile file: 613,691 bytes - 3 pages - 0 figures

1911. — Morgan, Thomas H.

Random segregation versus coupling in Mendelian inheritance

Science, 34:384.

PDF image facsimile file: 189,193 bytes - 1 page

1911. — Morgan, Thomas H.

The origin of five mutations in eye color in Drosophila and their modes of inheritance.

Science, New Series, 33:534-537.

PDF image facsimile file: 694,626 bytes - 4 pages - 0 figures

1911. — Morgan, Thomas H.

The origin of nine wing mutations in Drosophila.

Science, New Series, 33:496-499.

PDF image facsimile file: 688,689 bytes - 4 pages - 0 figures

1912. — Morgan, Thomas H.

Complete linkage in the second chromosome of the male of Drosophila

Science, 36:933-934.

PDF image facsimile file: 325,825 bytes - 2 pages

1913. — Castle, W. E.

Simplification of Mendelian formulae.

The American Naturalist, 47:170-182

PDF typeset file: 69,294 bytes - 13 pages - no figures

Soon after Mendel was rediscovered, the nature of the gene was being worked out. Along the way, many suggested changes to the symbology being used (e.g., B for dominant allele, b for recessive). Here Castle offers some suggestions for changing Mendelian symbols.

1913. — Morgan, Thomas H.

Factors and Unit Characters in Mendelian Heredity.

The American Naturalist, 47:5-16.

PDF image facsimile file: 741,353 bytes - 14 pages - 0 figures

1913. — Morgan, Thomas H.

Simplicity versus adequacy in Mendelian formulae

The American Naturalist, 47:372-374

PDF typeset file: 32,835 bytes - 6 pages - no figures

Soon after Mendel was rediscovered, the nature of the gene was being worked out. Along the way, many suggested changes to the symbology being used (e.g., B for dominant allele, b for recessive). Here Morgan offers some thoughts on changing Mendelian symbols.

1913. — Sturtevant, Alfred H.

The linear arrangement of six sex-linked factors in Drosophila, as shown by their mode of association.

Journal of Experimental Biology, 14:43-59.

PDF typeset file: 109,620 bytes - 22 pages - no figures

In 1998, with genome projects routinely producing detailed genetics maps of mice and men and every other sort of organism, it can be difficult to imagine a time when there were no genetic maps. The idea that individual genes occupy regular positions on chromosomes was one of the great insights of early genetics, and the very first genetic map was published in 1913 by Alfred H. Sturtevant, who was working on fruit flies in the laboratory of Thomas H. Morgan at Columbia University.

Sturtevant is now well known as one of the most important early pioneers in genetic research. However, at the time he produced the first map, he was an undergraduate. Many years later, Sturtevant (A History of Genetics) described how an undergraduate came to be crucially involved in establishing the very foundations of classical genetics:

In 1909, the only time during his twenty-four years at Columbia, Morgan gave the opening lectures in the undergraduate course in beginning zoology. It so happened that C. B. Bridges and I were both in the class. While genetics was not mentioned, we were both attracted to Morgan and were fortunate enough, though both still undergraduates, to be given desks in his laboratory the following year (1910-1911). The possibilities of the genetic study of Drosophila were then just beginning to be apparent; we were at the right place at the right time. In the latter part of 1911, in conversation with Morgan, I suddenly realized that the variations in strength of linkage, already attributed by Morgan to differences in the spatial separation of the genes, offered the possibility of determining sequences in the linear dimension of a chromosome. I went home and spent most of the night (to the neglect of my undergraduate homework) in producing the first chromosome map, which included the sex-linked genes y, w, v, m, and r, in the order and approximately the relative spacing that they still appear on the standard maps (Sturtevant, 1913).

1913. — Sturtevant, Alfred H.

The linear arrangement of six sex-linked factors in Drosophila, as shown by their mode of association.

Journal of Experimental Biology, 14:43-59.

PDF typeset file: 109,620 bytes - 22 pages - no figures

In 1998, with genome projects routinely producing detailed genetics maps of mice and men and every other sort of organism, it can be difficult to imagine a time when there were no genetic maps. The idea that individual genes occupy regular positions on chromosomes was one of the great insights of early genetics, and the very first genetic map was published in 1913 by Alfred H. Sturtevant, who was working on fruit flies in the laboratory of Thomas H. Morgan at Columbia University.

Sturtevant is now well known as one of the most important early pioneers in genetic research. However, at the time he produced the first map, he was an undergraduate. Many years later, Sturtevant (A History of Genetics) described how an undergraduate came to be crucially involved in establishing the very foundations of classical genetics:

In 1909, the only time during his twenty-four years at Columbia, Morgan gave the opening lectures in the undergraduate course in beginning zoology. It so happened that C. B. Bridges and I were both in the class. While genetics was not mentioned, we were both attracted to Morgan and were fortunate enough, though both still undergraduates, to be given desks in his laboratory the following year (1910-1911). The possibilities of the genetic study of Drosophila were then just beginning to be apparent; we were at the right place at the right time. In the latter part of 1911, in conversation with Morgan, I suddenly realized that the variations in strength of linkage, already attributed by Morgan to differences in the spatial separation of the genes, offered the possibility of determining sequences in the linear dimension of a chromosome. I went home and spent most of the night (to the neglect of my undergraduate homework) in producing the first chromosome map, which included the sex-linked genes y, w, v, m, and r, in the order and approximately the relative spacing that they still appear on the standard maps (Sturtevant, 1913).

1914. — Bridges, Calvin B.

Direct proof through non-disjunction that the sex-linked genes of Drosophila are borne on the X-chromosome.

Science, NS vol. XL:107-109.

PDF typeset file: 24,076 bytes - 5 pages - no figures

Although Bridges' longer 1916 Genetics paper (vol 1, page 1) on the same topic is better known and treats the issue at much greater length, this short communication in Science contains the same argument and is equally persuasive.

By 1910, much evidence had been presented to demonstrate that sexual phenotype (i.e., maleness or femaleness) was determined by chromosomes. And, as early as 1902 Sutton noted that similarities in the behavior of genes and chromosomes suggested that Mendelian factors might be carried on chromosomes.

Here, Bridges shows that mis-assortment of the sex chromosomes is accompanied by atypical inheritance patterns for sex-linked traits and he argues that this proves that genes are carried on chromosomes. He concludes his paper: "there can be no doubt that the complete parallelism between the unique behavior of the chromosomes and the behavior of sex-linked genes and sex in this case means that the sex-linked genes are located in and borne by the X-chromosomes."

1914. — Little, C. C.

A possible Mendelian explanation for a type of inheritance apparently non-Mendelian in nature

Science, 40:904-906.

PDF image facsimile file: 530,978 bytes - 3 pages

1915. — Morgan, Thomas H.

The Constitution of the Hereditary Material.

Proceedings of the American Philosophical Society, 54:143-153.

PDF image facsimile file: 424,504 bytes - 11 pages - 4 figures

1915. — Morgan, Thomas H., Sturtevant, A. H., Muller, H. J., and C. B. Bridges

The Mechanism of Mendelian Heredity.

New York: Henry Holt and Company

This is a full-text PDF image facsimile version of the entire 262-page original book.

This book, by T. H. Morgan and his students, is the first work to articulate a comprehensive, mechanistic model to explain Mendelian patterns of inheritance.

Although Mendelism had quickly been accepted as a good phenomenological explanation for the patterns seen in Mendelian crosses, until the work of Morgan's group, it was still possible to consider Mendelism to be a purely theoretical model of heredity. As Morgan's group first established the relationship of genes to chromosomes, then developed the first genetic map, and went on to describe a variety of interactions between chromosomes and Mendelian factors, the conclusions they offered became inescapable - genes are physical objects, carried on chromosomes in static locations.

Morgan's group made genes real and this book is the first full-length presentation of their findings. It revolutionized the study of heredity.

1915. — Shull, G. H.

Genetic Definitions in the New Standard Dictionary.

The American Naturalist, 49:52-59.

PDF typeset file: 78,002 bytes - 12 pages - no figures

In this short paper, Shull takes exception to some recently published dictionary definitions of many technical genetics terms and he offers corrected definitions in their stead. The main value of this paper to modern readers is that it gives a very good idea of what geneticists (or at least this geneticist) meant by their use of genetic terminology at the time. Although many of Shull's proffered definitions would be at home in a modern biology text, some are no longer in current usage.

Shull could have done a better job of defining "alternative inheritance" by adding "contrast with continuous inheritance," since at the time of his writing there was still a school of thought that argued that most heritable variation was continuous but that Mendelian theories provided explanations only for cases of "alternative inheritance," which were rare in nature and might only represent artifacts of inheritance in domesticated organisms.

For just such a criticism of alternative inheritance, see Weldon, W. F. R. 1902 Mendel's laws of alternative inheritance in peas. Biometrika, 1:228-254.

1916. — East, E. M.

Studies on Size Inheritance in Nicotiana

Genetics, 1:164-176.

PDF image facsimile file

1916. — Ibsen, Heman L.

Tricolor Inheritance. II. the Basset Hound

Genetics, 1: 367-376.

PDF image facsimile file

1916. — Ibsen, Heman L.

Tricolor Inheritance. III. Tortoiseshell Cats

Genetics, 1: 377-386.

PDF image facsimile file

1916. — Ibsen, Heman L.

Tricolor Inheritance. I. the Tricolor Series in Guinea-pigs

Genetics, 1: 287-309.

PDF image facsimile file

1916. — Muller, Hermann J.

The Mechanism of Crossing-over.

New York: The American Naturalist

This is an image facsimile version of the entire 86-page original edition.

Beginning 1910, T. H. Morgan and his students established the foundations of modern genetics by demonstrating that genes were real — not theoretical — entities.

This work is a collection of papers that represented the doctoral dissertation of one of those students - H. J. Muller.

1916. — Bridges, Calvin B.

Non-disjunction as proof of the chromosome theory of heredity (part 1).

Genetics, B, 1:1-52.

PDF image facsimile file: 1.808,605 bytes - 52 pages - many figures

This paper was published as the first article in the first volume the new journal genetics. As the title states, the paper offered PROOF that genes are real, physical things that are carried on chromosomes.

This article was scanned from Alfred Sturtevant's personal copy of Genetics. Access to the journal was provided by Edward B. Lewis and Elliot M. Meyerowitz of the California Institute of Technology.

1916. — Bridges, Calvin B.

Non-disjunction as proof of the chromosome theory of heredity (part 2).

Genetics, B, 1:107-163.

PDF image facsimile file: 2,600,250 bytes - 59 pages - many figures

This paper was published as the first article in the first volume the new journal genetics. As the title states, the paper offered PROOF that genes are real, physical things that are carried on chromosomes.

This article was scanned from Alfred Sturtevant's personal copy of Genetics. Access to the journal was provided by Edward B. Lewis and Elliot M. Meyerowitz of the California Institute of Technology.

1917. — Bridges, Calvin B.

Deficiency.

Genetics, 2:445-465.

PDF image facsimile file: 21 pages

1917. — Davenport, Charles B.

Inheritance of Stature

Genetics, 2: 313-389.

PDF image facsimile file

1917. — Goldschmidt, Richard

Crossing Over ohne Chiasmatypie?

Genetics, 2:82-95.

PDF image facsimile file: 764,480 bytes - 14 pages - 2 figures

1917. — Little, C. C.

The Relation of Yellow Coat Color and Black-eyed White Spotting of Mice in Inheritance

Genetics, 2: 433-444.

PDF image facsimile file

1917. — Morgan, Thomas H.

The Theory of the Gene.

The American Naturalist, 51:513-544.

PDF typeset file: 3,116,439 bytes - 28 pages - 9 figures

In 1909, Morgan expressed doubts about the methods of Mendelian inheritance. Then, in 1910, a white-eyed mutant fly turned up in Morgan’s laboratory and studies on the inheritance of the white-eyed trait suggested that the gene producing the trait was carried on the X-chromosome. This strongly suggested that Mendelian genes were real, not th The Mechanism of Mendelian Heredity.

In this paper, Morgan discusses The Theory of the Gene, as established in his laboratory.

1917. — Sturtevant, A. H.

Crossing Over without Chiasmatype?

Genetics, 2:301-304.

PDF image facsimile file: 220,991 bytes - 4 pages - no figures

1918. — Charles W. Metz, Charles W.

The Linkage of Eight Sex-linked Characters in Drosophila virilis

Genetics, 3: 107-134.

PDF image facsimile file

1918. — Muller, Hermann J.

Genetic Variability, Twin Hybrids and Constant Hybrids, in a Case of Balanced Lethal Factors

Genetics, 3: 422-499.

PDF image facsimile file

1918. — Muller, Hermann J.

Genetic variability, twin hybrids and constant hybrids, in a case of balanced lethal factors.

Genetics, 3:422-499.

PDF image facsimile file: 78 pages

1918. — Vries, Hugo de

Mutations of Oenothera suaveolens desf.

Genetics, 3:1-26.

PDF image facsimile file: 26 pages

1918. — Vries, Hugo de

Twin hybrids of Oenothera hookeri T. and G..

Genetics, 3:397-421.

PDF image facsimile file: 25 pages

1918. — Weinstein, Alexander

Coincidence of Crossing Over in drosophila Melanogaster (ampelophila)

Genetics, 3: 135-172.

PDF image facsimile file

1918. — Wright, Sewall

On the nature of size factors.

Genetics, 3:367-374.

PDF image facsimile file: 8 pages - 0 figures

1919. — Bridges, Calvin B. and Mohr, Otto L.

The Inheritance of the Mutant Character "vortex"

Genetics, 4: 283-306.

PDF image facsimile file

1919. — Bridges, Calvin B., and Mohr, Otto L.

The inheritance of the mutant character "vortex".

Genetics, 4:283-306.

PDF image facsimile file: 24 pages

1919. — Castle, W.E.

Is the arrangement of the genes in the chromosome linear?

Proceedings of the National Academy of Sciences, 5:25-32.

PDF image facsimile file: 615,957 bytes - 8 pages

1919. — Fisher, R. A.

The Genesis of Twins

Genetics, 4: 489-499.

PDF image facsimile file

1919. — Ibsen, Heman L.

Tricolor Inheritance. Iv. the Triple Allelo-morphic Series in Guinea-pigs

Genetics, 4: 597-606.

PDF image facsimile file

1919. — Morgan, Thomas H.

The Physical Basis of Heredity.

Philadelphia: J. B. Lippincott Company

This is a full-text PDF image facsimile version of the entire 305-page original book.

In this book, T. H. Morgan (who would later receive the first Nobel Prize for genetics research) describes the model of heredity developed at Columbia by Morgan and his students.

The foundations of genetics were laid down by Mendel, and these were brought to the world's attention when his work was rediscovered by Correns, de Vries, and von Tschermak in 1900. But the real establishment of genetics as a real science, with a known physical basis, did not occur until the work outlined in this book became generally known.

To understand the true conceptual underpinnings of classical genetics, one must read the publications from "The Fly Room" at Columbia.

1919. — Sturtevant, A. H., Bridges, C. B., and Morgan, T. H.

The spatial relations of genes.

Proceedings of the National Academy of Sciences, 5:168-173.

PDF image facsimile file: 727,921 bytes - 6 pages

1920. — Altenburg, Edgar and Muller, Hermann J.

The Genetic Basis of Truncate Wing,—an Inconstant and Modifiable Character in Drosophila

Genetics, 5: 1-59.

PDF image facsimile file

1920. — Altenburg, Edgar and Muller, Hermann J.

The Genetic Basis of Truncate Wing,—an Inconstant and Modifiable Character in Drosophila

Genetics, 5: 248.

PDF image facsimile file

1920. — Dunn, L. C.

Independent Genes in Mice

Genetics, 5: 344-361.

PDF image facsimile file

1920. — Dunn, L. C.

Linkage in Mice and Rats

Genetics, 5: 325-343.

PDF image facsimile file

1920. — Sturtevant, Alfred H.

Genetic studies on Drosophila simulans. I. Introduction. Hybrids with Drosophila melanogaster.

Genetics, 5:488-500.

PDF image facsimile file: 13 pages - 5 figures

1921. — Bridges, Calvin.

Triploid intersexes in Drosophila melanogaster.

Science, 54:252-254.

PDF typeset file: 153,521 bytes - 5 pages - no figures

Work in the laboratory of T. H. Morgan was critical in establishing that genes are real, physical entities and that they are arranged in a linear order on chromosomes. Calvin Bridges was a key player in the Morgan group. In 1914, Bridges first demonstrated that a correlation existed between the incorrect assortment of X chromosomes and the incorrect assortment of some genes. In 1916, he expanded on that work to "prove" that sex-linked genes in Drosophila are carried on the X chromosome.

In this paper, Bridges shows that the correlation between mis-assortment of genes and chromosomes applies to the autosomes as well as to the sex chromosomes. In addition, he shows that sex determination in Drosophila appears to be driven by the ratio of X chromosomes to autosomes, not by the absolute number of X chromosomes.

1921. — Sturtevant, Alfred H.

Genetic studies on Drosophila simulans. II. Sex-linked groups of genes.

Genetics, 6:43-64.

PDF image facsimile file: 22 pages - 5 figures

1921. — Sturtevant, Alfred H.

Genetic studies on Drosophila simulans. III. Autosomal genes. General discussion.

Genetics, 6:179-207.

PDF image facsimile file: 29 pages - 6 figures

1921. — Wright, Sewall

Systems of mating. I. The biometric relations between parent and offspring.

Genetics, 6:111-123.

PDF image facsimile file: 13 pages - 2 figures

1921. — Wright, Sewall

Systems of mating. II. The effects of inbreeding on the genetic composition of a population.

Genetics, 6:124-143.

PDF image facsimile file: 20 pages - 12 figures

1921. — Wright, Sewall

Systems of mating. III. Assortative mating based on somatic resemblance.

Genetics, 6:144-161.

PDF image facsimile file: 18 pages - 7 figures

1921. — Wright, Sewall

Systems of mating. IV. The effects of selection.

Genetics, 6:162-166.

PDF image facsimile file: 5 pages - 1 figure

1921. — Wright, Sewall

Systems of mating. V. General considerations.

Genetics, 6:167-178.

PDF image facsimile file: 12 pages - 7 figures

1922. — Morgan, Thomas H.

Croonian Lecture: On the Mechanism of Heredity.

Proceedings of the Royal Society, B, 94:162-197.

PDF typeset file: 3,916,605 bytes - 42 pages - 35 figures

The Croonian Lecture is the Royal Society's premier lecture in the biological sciences. Dr Croone, one of the original members of the Society, left on his death in 1684 a scheme for two lectureships, one at the Royal Society and the other at the Royal College of Physicians

Morgan was invited to give the Croonian lecture in 1922 - a recognition of his pioneering work in elucidating the physical basis of heredity.

1922. — Muller, Hermann J.

Variation due to change in the individual gene.

The American Naturalist, 56:32-50.

PDF typeset file: 69,751 bytes - 17 pages - no figures

This paper is from an address given by to the thirty-ninth annual meeting of the American Society of Naturalists, held in Toronto on 29 December 29 1921.

In this remarkably prescient analysis, Muller lays out the paradoxical nature of the genetic material. It is apparently both autocatalytic (i.e., directs its own synthesis) and heterocatalytic (i.e., directs the synthesis of other molecules), yet only the heterocatalytic function seems subject to mutation. With this, he defines the key problems that must be solved for a successful chemical model of the gene.

Muller also anticipated the ultimate development of molecular genetics:

That two distinct kinds of substances — the d'Hérelle substances (NOTE: viruses) and the genes — should both possess this most remarkable property of heritable variation or "mutability," each working by a totally different mechanism, is quite conceivable, considering the complexity of protoplasm, yet it would seem a curious coincidence indeed. It would open up the possibility of two totally different kinds of life, working by different mechanisms. On the other hand, if these d'Hérelle bodies were really genes, fundamentally like our chromosome genes, they would give us an utterly new angle from which to attack the gene problem. They are filterable, to some extent isolable, can be handled in test tubes, and their properties, as shown by their effects on the bacteria, can then be studied after treatment. It would be very rash to call these bodies genes, and yet at present we must confess that there is no distinction known between the genes and them. Hence we cannot categorically deny that perhaps we may be able to grind genes in a mortar and cook them in a beaker after all. Must we geneticists become bacteriologists, physiological chemists and physicists, simultaneously with being zoologists and botanists? Let us hope so.

1922. — Shull, A. Franklin

Ten Years of Heredity.

Transactions of the American Microscopical Society, 41:82-100.

PDF image facsimile file: 909,722 bytes - 19 pages - 8 figures

1923. — Castle, W. E.

The relation of Mendelism to mutation and evolution.

The American Naturalist, 57:559-561

PDF typeset file: 30,865 bytes - 5 pages - no figures

Here Castle offers a short note relating the behavior of simple Mendelian characters to the more complex, quantitative traits found in natural populations (and thus of interest to those studying evolution).

1923. — Demerec, M.

Inheritance of White Seedlings in Maize

Genetics, 8: 561-593.

PDF image facsimile file

1923. — East - Morgan - Harris - Shull

The Centenary of Gregor Mendel and of Francis Galton.

The Scientific Monthly, 16: 225-270.

PDF typeset file: 247,951 bytes - 54 pages - no figures

In December of 1922, the American Society of Naturalists held a special session to honor the centenaries of the birth of Gregor Mendel and of Francis Galton. This is the collection of the four papers presented at that session and later published in the The Scientific Monthly.

1923. — East, E. M.

Mendel and his contemporaries.

The Scientific Monthly, 16: 225-237.

PDF typeset file: 247,951 bytes - 54 pages - no figures

In December of 1922, the American Society of Naturalists held a special session to honor the centenaries of the birth of Gregor Mendel and of Francis Galton. This is one of the four papers presented at that session and later published in the The Scientific Monthly.

1923. — Garrod, Archibald.

Inborn Errors of Metabolism, Second Edition.

London: Henry Frowde and Hodder & Stoughton

This is a full-text PDF image facsimile version of the entire 216-page original book.

Less than two years after the rediscovery of Mendelism and just a few years after the word biochemistry was first coined, Garrod reported on alkaptonuria in humans and came to the conclusion that it was inherited as a Mendelian recessive and that the occurrence of mutations (sports in the word of the time) in metabolic function should be no more surprising than inherited variations in morphology.

In 1908, he summarized his thinking about "inborn errors of metabolism" (his term for what we would now think of as mutations in genes affecting metabolic function) in a book. An image facsimile of the second edition (1923) of that book is presented here.

Like Mendel's work, Garrod's insights were so far ahead of their time that his entire work on metabolic mutations was largely neglected, until later efforts to elucidate the physiological functioning of genes led to the Nobel-prize-winning one-gene, one-enzyme hypothesis.

1923. — Harris, J. Arthur

Galton and Mendel: Their contribution to genetics and their influence on biology.

The Scientific Monthly, 16: 247-263.

PDF typeset file: 247,951 bytes - 54 pages - no figures

In December of 1922, the American Society of Naturalists held a special session to honor the centenaries of the birth of Gregor Mendel and of Francis Galton. This is one of the four papers presented at that session and later published in the The Scientific Monthly.

1923. — Morgan, Thomas H.

The bearing of Mendelism on the origin of species.

The Scientific Monthly, 16: 237-247.

PDF typeset file: 247,951 bytes - 54 pages - no figures

In December of 1922, the American Society of Naturalists held a special session to honor the centenaries of the birth of Gregor Mendel and of Francis Galton. This is one of the four papers presented at that session and later published in the The Scientific Monthly.

1923. — Shull, George H.

A permanent memorial to Galton and Mendel.

The Scientific Monthly, 16: 263-270.

PDF typeset file: 247,951 bytes - 54 pages - no figures

In December of 1922, the American Society of Naturalists held a special session to honor the centenaries of the birth of Gregor Mendel and of Francis Galton. This is one of the four papers presented at that session and later published in the The Scientific Monthly.

1923. — Sturtevant, Alfred H.

Inheritance of the direction of coiling in Limnaea.

Science, 58:269-270.

PDF typeset file: 150,314 bytes - 7 pages - no figures

As evidence mounted for the chromosomal basis of inheritance, occasional examples were discovered that seemed to challenge the Mendelian model, as mapped to the chromosomes by T. H, Morgan and his students. In this paper, A. H. Sturtevant (one of Morgan's students) shows that apparently aberrant patterns of inheritance can be seen to correspond to the Mendelian model, if care is taken to assign phenotype to the correct individual.

The case in question is the direction of shell coiling in snails of the genus Limnaea. These shells can either coil to the right (dextral) or left (sinistral). Coiling seemed to be an inherited trait, except that the observed patterns of inheritance were strange. Broods of offspring from sinistral snails, produced by self-fertilization (these snails are hermaphroditic) were either all sinistral or all dextral (never some of each). The same was found true if the single parent was dextral. Complicated models had been offered to explain these results, but here Sturtevant shows that a much simpler model is equally effective:

An analysis of the data presented suggests that the case is a simple Mendelian one, with the dextral character dominant, but with the nature of a given individual determined, not by its own constitution but by that of the unreduced egg from which it arose.

A similar problem exists with the color of bird eggs. Chickens, for example, can produce eggs that are either brown or white, and these colors are genetically determined. However, the trait "shell color" is an attribute of the hen laying the eggs, not of the chick that hatches out of the egg. When you realize that the shell is created as a secretion in the hen's oviducts, this makes perfect sense, even though the actual egg shell is ultimately separate from the body of the hen and is part of the egg from which the chick hatches.

The direction of shell coiling is now known to be controlled by specific proteins present in the cytoplasm of the egg. These proteins are produced early in egg development, prior to fertilization, and so are produced solely from genes present in the mother. Just as with the color of egg shells in chickens, the direction of shell coiling in Limnaea is really part of the phenotype of the mother of the snail, not of the snail actually wearing the shell.

1923. — Taliaferro, W. H., and Huck, J. G.

The Inheritance of Sickle-cell Anaemia in Man

Genetics, 8: 594-598.

PDF image facsimile file

1923. — Vries, Hugo de, and Boedijn, K.

On the distribution of mutant characters among the chromosomes of Oenothera lamarckiana.

Genetics, 8:233-238.

PDF image facsimile file: 6 pages

1924. — Castle, W. E., and Wachter, W. L.

Variations of Linkage in Rats and Mice

Genetics, 9: 1-12.

PDF image facsimile file

1924. — Payne, F.

Crossover Modifiers in the Third Chromosome of Drosophila melanogaster

Genetics, 9: 327-342.

PDF image facsimile file

1924. — Riddle, Oscar.

Any Hereditary Character and the Kinds of Things We Need to Know About It.

The American Naturalist, LVIII:410-425.

PDF typeset file: 80,148 bytes - 13 pages - no figures

This does not qualify as a classic genetics paper and I suspect that it has never before been included in a collection of important papers. However, it is included here because it provides a glimpse into some general aspects of genetic thought in the mid 1920's.

The premise of this essay is essentially that, as of its writing, " studies on heredity and evolution offer what is mainly a two-sided attack on a many-sided problem." This argument was well taken, but the modern reader may have difficulty appreciating other concerns of the essay.

1924. — Snyder, Laurence H.

The Inheritance of the Blood Groups

Genetics, 9: 465-478.

PDF image facsimile file

1925. — Bridges, Calvin B., and Anderson, E. G.

Crossing over in the X chromosomes of triploid females of Drosophila melanogaster..

Genetics, 10:418-441.

PDF image facsimile file: 24 pages

1925. — Castle, W. E.

A Sex Difference in Linkage in Rats and Mice

Genetics, 10: 580-582.

PDF image facsimile file

1925. — Morgan, L. V.

Polyploidy in drosophila Melanogaster with Two Attached X Chromosomes

Genetics, 10: 148-178.

PDF image facsimile file

1925. — Muller, H. J. and Jacobs-Muller, Jessie M.

The Standard Errors of Chromosome Distances and Coincidence

Genetics, 10: 509-524.

PDF image facsimile file

1925. — Muller, Hermann J.

The regionally differential effect of X rays on crossing over in autosomes of Drosophila.

Genetics, 10:470-507.

PDF image facsimile file: 38 pages

1925. — Muller, Hermann J., and Jacobs-Muller, Jessie M.

The standard errors of chromosome distances and coincidence.

Genetics, 10:509-524.

PDF image facsimile file: 16 pages

1925. — Sturtevant, Alfred H.

The effects of unequal crossing over at the bar locus in Drosophila.

Genetics, 10:117-147.

PDF image facsimile file: 31 pages - 10 figures

1925. — Vries, Hugo De

Mutant Races Derived from Oenothera Lamarckiana Semigigas

Genetics, 10: 211-222.

PDF image facsimile file

1925. — Vries, Hugo de

Mutant races derived from Oenothera lamarckiana semigigas.

Genetics, 10:211-222.

PDF image facsimile file: 12 pages

1925. — Wright, Sewall

The factors of the albino series of guinea-pigs and their effects on black and yellow pigmentation.

Genetics, 10:223-260.

PDF image facsimile file: 38 pages - 5 figures

1926. — Alberts, Hugo W.

A Method For Calculating Linkage Values

Genetics, 11: 235-248.

PDF image facsimile file

1926. — Bridges, Calvin B., and Olbrycht, T. M.

The Multiple Stock "xple" and its use.

Genetics, 11:41-55.

PDF image facsimile file: 16 pages

1926. — Stadler, L. J.

The Variability of Crossing Over in Maize

Genetics, 11: 1-37.

PDF image facsimile file

1926. — Stern, Curt and Bridges, Calvin B.

The Mutants of the Extreme Left End of the Second Chromosome of Drosophila melanogaster

Genetics, 11: 503-530.

PDF image facsimile file

1926. — Wright, Sewall and Eaton, O. N.

Mutational Mosaic Coat Patterns of the Guinea Pig

Genetics, 11: 333-351.

PDF image facsimile file

1927. — Muller, Hermann J.

Artificial transmutation of the gene.

Science, 46:84-87.

PDF image facsimile file: 1,002,392 bytes - 4 pages

1927. — Wright, Sewall

The effects in combination of the major color-factors of the guinea pig

Genetics, 12: 530-569.

PDF image facsimile file

1928. — Morgan, Thomas H.

The Theory of the Gene, Revised and Enlarged Edition.

New Haven: Yale University Press

This is a full-text PDF image facsimile version of the entire 358-page original book.

This book, by T. H. Morgan, summarizes the state of knowledge on classical genetics in the mid 1920's.

Although Mendelism had quickly been accepted as a good phenomenological explanation for the patterns seen in Mendelian crosses, until the work of Morgan's group, it was still possible to consider Mendelism to be a purely theoretical model of heredity. As Morgan's group first established the relationship of genes to chromosomes, then developed the first genetic map, and went on to describe a variety of interactions between chromosomes and Mendelian factors, the conclusions they offered became inescapable – genes are physical objects, carried on chromosomes in static locations.

Less than 15 years after Morgan first started working with fruit flies, the foundations for a theory of the gene had been worked out – largely by Morgan and students working in his laboratory.

1928. — Muller, Hermann J.

The measurement of gene mutation rate in Drosophila, its high variability, and its dependence upon temperature.

Genetics, 13:279-357.

PDF image facsimile file: 79 pages

1928. — Painter, Theophilus S.

A Comparison of the Chromosomes of the Rat and Mouse with Reference to the Question of Chromosome Homology in Mammals

Genetics, 13: 180-189.

PDF image facsimile file

1928. — Sturtevant, A. H.

A Further Study of the So-call Mutation at the Bar Locus of Drosophila

Genetics, 13:401-409

PDF image facsimile file

1928. — Sturtevant, Alfred H.

A further study of the so-called mutation at the bar locus of Drosophila.

Genetics, 13:401-409.

PDF image facsimile file: 9 pages - no figures

1928. — Wright, Sewall

An eight-factor cross in the guinea pig

Genetics, 13: 508-531.

PDF image facsimile file

1929. — East, E. M.

The concept of the gene.

Proceedings of the International Congress of Plant Sciences, Ithaca, New York, August 16-23, 1926, vol. 1. Menasha, WI: George Banta Publishing Co. pp 889-895.

PDF typeset file: 76,104 bytes - 11 pages - no figures

As classical genetics acquired more and more explanatory power, the question what is a gene? became more important. Were genes real physical entities, or merely theoretical concepts that allowed for the mathematical modelling of inheritance. This paper represents one effort to consider The concept of the gene. The paper's opening paragraph sets the tone:

Nearly fifteen years ago I attempted to defend the thesis that the Mendelian method of recording the facts of inheritance was simply a notation useful as a description of physiological facts. The argument was an elaboration of the proposition that the germ-cell unit of heredity, the gene, was an abstract, formless, characterless concept used for convenience in describing the results of breeding experiments. It was the ghost of an entity which might later be clothed with flesh, but its usefulness at the time was due to its adaptability to mathematical treatment. By postulating that the results derived from controlled matings were due to the activities of definite germ-cell units which could be manipulated arithmetically, investigators were able to formulate new experimental tests, and thus to open the way to further discovery; but these units could be given no intelligible interpretation in terms of geometry, chemistry, or physiology.

In the last paragraph, East asserts:

We arrive, therefore, at the same port from which we departed when our discussion began. The genes are units useful in concise descriptions of the phenomena of heredity. Their place of residence is the chromosomes. Their behavior brings about the observed facts of genetics. For the rest, what we know about them is merely an interpretation of crossover frequency. In terms of geometry, chemistry, physics or mechanics, we can give them no description whatever.

1929. — McClintock, Barbara

A cytological and genetical study of triploid maize

Genetics, 14: 180-222.

PDF image facsimile file

1929. — Schultz, Jack

The minute reaction in the development of Drosophila melanogaster

Genetics, 14: 366-419.

PDF image facsimile file

1930. — Davenport, C. B.

Sex linkage in man

Genetics, 15: 401-444.

PDF image facsimile file

1930. — Dobzhansky, T.

Translocations involving the third and the fourth chromosomes of Drosophila melanogaster

Genetics, 15: 347-399.

PDF image facsimile file

1930. — Muller, Hermann J., and Altenburg, Edgar.

The frequency of translocations produced by X-rays in Drosophila.

Genetics, 15:283-311.

PDF image facsimile file: 29 pages

1930. — Patterson, J. T. and Muller, H. J.

Are "progressive" mutations produced by X-rays?

Genetics, 15: 495-577.

PDF image facsimile file

1931. — Creighton, Harriet B., and McClintock, Barbara.

A correlation of cytological and genetical crossing-over in Zea mays.

PNAS, 17:492-497.

PDF typeset file: 140,176 bytes - 17 pages - several figures

When Alfred Sturtevant created the first genetic map, he hypothesized that genetic recombination resulted from the actual exchange of chromatid fragments. However, at the time there was no hard evidence that proved recombination is accomplished via such a mechanism. The same genetic results could be explained if only alleles are exchanged during recombination, leaving the bulk of the chromatid arm unaffected. Since the two hypotheses make equivalent predictions regarding the distribution of alleles, they cannot be distinguished using purely genetic methods.

Attempting to demonstrate that genetic recombination is accomplished via the physical exchange of chromatid arms poses a problem similar to that encountered by Thomas H. Morgan when he first hypothesized that genes might be carried on the X chromosome. Although Morgan's genetic hypothesis of X-linkage provided an explanation for the inheritance of the white-eye allele in Drosophila, the notion that genes are actually carried on the X chromosome was not proven until Calvin Bridges provided cytological evidence to confirm the genetic observations. Bridges established a one-to-one correspondence between the abnormal distribution of eye-color alleles and the abnormal distribution of X chromosomes. That is, he established a relationship between genetic markers (the eye color alleles and their associated inheritance patterns) and cytological markers (the presence of abnormal sets of sex chromosomes).

In this paper, Creighton and McClintock present work in which they use a combination of cytological and genetic markers to show that cytological crossing-over occurs and that it is accompanied by genetical crossing-over. In just a few pages the authors accomplish their goal of establishing the reality of cytological recombination and of showing that it is associated with genetic recombination. This paper is truly a classic.

If this paper is read in isolation, the authors' discussion of their results can, at times, be difficult to follow. When this paper was originally published, however, it was accompanied by another paper (by McClintock) that immediately preceded it in the journal and that was intended to serve as an introduction to this paper. In the preceding paper, McClintock provided the basic genetic and cytological information necessary to understand the experimental logic of this paper. The background paper is The order of the genes C, Sh, and Wx in Zea mays with reference to a cytologically known point in the chromosome. The two papers should be read together, with the first, descriptive paper serving as a critical and necessary introduction to the second, experimental work.

For additional commentary on Creighton and McClintock's important work, see Edward Coe and Lee B. Kass (2005) Proof of physical exchange of genes on the chromosomes. Proceedings of the National Academy of Sciences, USA. 102:6641-6646.

1931. — Creighton, Harriet B., and McClintock, Barbara.

A correlation of cytological and genetical crossing-over in Zea mays.

PNAS, 17:492-497.

PDF image facsimile file: 6 pages - several figures

When Alfred Sturtevant created the first genetic map, he hypothesized that genetic recombination resulted from the actual exchange of chromatid fragments. However, at the time there was no hard evidence that proved recombination is accomplished via such a mechanism. The same genetic results could be explained if only alleles are exchanged during recombination, leaving the bulk of the chromatid arm unaffected. Since the two hypotheses make equivalent predictions regarding the distribution of alleles, they cannot be distinguished using purely genetic methods.

Attempting to demonstrate that genetic recombination is accomplished via the physical exchange of chromatid arms poses a problem similar to that encountered by Thomas H. Morgan when he first hypothesized that genes might be carried on the X chromosome. Although Morgan's genetic hypothesis of X-linkage provided an explanation for the inheritance of the white-eye allele in Drosophila, the notion that genes are actually carried on the X chromosome was not proven until Calvin Bridges provided cytological evidence to confirm the genetic observations. Bridges established a one-to-one correspondence between the abnormal distribution of eye-color alleles and the abnormal distribution of X chromosomes. That is, he established a relationship between genetic markers (the eye color alleles and their associated inheritance patterns) and cytological markers (the presence of abnormal sets of sex chromosomes).

In this paper, Creighton and McClintock present work in which they use a combination of cytological and genetic markers to show that cytological crossing-over occurs and that it is accompanied by genetical crossing-over. In just a few pages the authors accomplish their goal of establishing the reality of cytological recombination and of showing that it is associated with genetic recombination. This paper is truly a classic.

If this paper is read in isolation, the authors' discussion of their results can, at times, be difficult to follow. When this paper was originally published, however, it was accompanied by another paper (by McClintock) that immediately preceded it in the journal and that was intended to serve as an introduction to this paper. In the preceding paper, McClintock provided the basic genetic and cytological information necessary to understand the experimental logic of this paper. The background paper is The order of the genes C, Sh, and Wx in Zea mays with reference to a cytologically known point in the chromosome. The two papers should be read together, with the first, descriptive paper serving as a critical and necessary introduction to the second, experimental work.

For additional commentary on Creighton and McClintock's important work, see Edward Coe and Lee B. Kass (2005) Proof of physical exchange of genes on the chromosomes. Proceedings of the National Academy of Sciences, USA. 102:6641-6646.

1931. — Dobzhansky, t.

Translocations Involving the Second and the fourth chromosomes of Drosophila melanogaster

Genetics, 16: 629-658.

PDF image facsimile file

1931. — Haldane, J. B. S. and Waddington, C. H.

Inbreeding and Linkage

Genetics, 16: 357-374.

PDF image facsimile file

1931. — McClintock, Barbara and Hill, Henry E.

The cytological identification of the chromosome associated with the r-g linkage group in Zea mays

Genetics, 16: 175-190.

PDF image facsimile file

1931. — McClintock, Barbara.

The order of the genes C, Sh, and Wx in Zea mays with reference to a cytologically known point in the chromosome.

PNAS, 17:485-491.

PDF image facsimile file: 7 pages - several figures

In this paper, McClintock provides the basic genetic and cytological information necessary to understand the logic of her classic work with Harriet Creighton: A correlation of cytological and genetical crossing-over in Zea mays that appeared immediately following this paper in PNAS.

For additional commentary on Creighton and McClintock's important work, see Edward Coe and Lee B. Kass (2005) Proof of physical exchange of genes on the chromosomes. Proceedings of the National Academy of Sciences, USA. 102:6641-6646.

1931. — Thompson, David H.

The side-chain theory of the structure of the Gene

Genetics, 16: 267-290.

PDF image facsimile file

1931. — Wright, Sewall

Evolution in Mendelian populations.

Genetics, 16:97-159.

PDF image facsimile file: 63 pages - 21 figures

1931. — Wright, Sewall.

Evolution in Mendelian populations.

Genetics, 16:97-159.

PDF image facsimile file: 3.037,667 bytes - 63 pages - several figures

Soon after the establishment of Mendelian genetics, several workers began to explore how Mendelian mechanisms would affect changes in gene frequencies in populations — that is, they began to explore the implications of Mendelism for evolution.

Sewall Wright became one of the leading theoreticians who studied Mendelism in the context of population genetics. This paper is a key presentation of his thinking on how Mendelism and evolution might interact.

1932. — Fisher, R. A. , Immer, F. R., and Tedin, Olof

The Genetical Interpretation of Statistics of the Third Degree in the Study of Quantitative Inheritance

Genetics, 17: 107-124.

PDF image facsimile file

1932. — Jones, Donald F. (ed)

Proceedings of the Sixth International Congress of Genetics, Vol. I.

Austin, Texas: Genetics Society of America

This is an image facsimile version of the entire 396-page original edition.

The Proceedings of the Sixth International Congress of Genetics, held in 1932, offers a glimpse into classical genetics at the height of its power and influence. Thomas Morgan, who had just received the first Nobel Prize ever awarded in genetics, served as president of the congress.

The participants list reads like a who's who of classical genetics: The three rediscovers of Mendel - Correns, de Vries, and von Tschermak - all attended the meeting. Morgan, Sturtevant, and Muller gave talks. Population genetics and the relationship of genetics to evolution was discussed by R. A. Fisher, J. B. S. Haldane, and Sewall Wright.

According to the Treasurer's Report, the total cost of the meeting was $17,583.58.

1932. — Wright, Sewall

General, Group and Special Size Factors

Genetics, 17: 603-619.

PDF image facsimile file

1932. — Wright, Sewall.

Complementary Factors for Eye Color in Drosophila.

The American Naturalist, LXVI:282-283.

PDF typeset file: 7,701 bytes - 2 pages - no figures

There are two distinct biochemical pathways producing pigments that color the eyes of Drosophila melanogaster — one yields a bright red pigment, the other brown. When both are present, the eyes are dark-red. When one is present and the other absent, flies have brown or bright red eyes. When both are missing, flies have white eyes.

In 1932, Sewall Wright reported the first case where a cross between red-eyed and brown-eyed flies yielded double-recessive progeny with white eyes. What makes this observation interesting is that the work occurred as part of a class exercise in an undergraduate teaching laboratory at the University of Chicago. Not many modern undergraduate lab exercises yield publishable results.

1933. — Belling, John

Crossing Over and Gene Rearrangement in Flowering Plants

Genetics, 18: 388-413.

PDF image facsimile file

1933. — Demerec, Milislav

What is a Gene?

Journal of Heredity, 24:368-378.

PDF typeset file: 679,936 bytes - 22 pages - several figures

Once the foundations of transmission genetics had been worked out, researchers began to consider what the chemical nature of the gene might be. Here Milislav Demerec offers one of the first such efforts. He concludes that the gene is a minute organic particle, capable of reproduction, located in a chromosome and responsible for the transmission of a hereditary characteristic. Moreover, he states that the available evidence suggests that genes are uni-molecular, and he notes:

If a gene is a complex organic molecule it would be expected to be similar in composition to other complex molecules, viz. molecular groups constituting this molecule (whatever these groups may be) would he arranged in chains and side chains. He then offers a drawing of the structure of DNA (!) as an example of a complex organic molecule, but is quick to add that The diagram is not intended to give any implication as to the number, the type, or the arrangement of the molecules in a gene group. Its purpose is to illustrate the molecular structure of a complex organic molecule.

Another 20 years would have to pass before the true chemical nature of the gene would be established.

1933. — Macarthur, John W.

Sex-linked Genes in the Fowl

Genetics, 18: 210-220.

PDF image facsimile file

1933. — Morgan, L. V.

A Closed X Chromosome in Drosophila Melanogaster

Genetics, 18: 250-283.

PDF image facsimile file

1933. — Patterson, J. T.

The Mechanism of Mosaic Formation in Drosophila

Genetics, 18: 32-52.

PDF image facsimile file

1933. — Rhoades, Marcus M.

An Experimental and Theoretical Study of Chromatid Crossing Over

Genetics, 18: 535-555.

PDF image facsimile file

1933. — Schultz, Jack

X-ray Effects on Drosophila Pseudo-obscura

Genetics, 18: 284-291.

PDF image facsimile file

1933. — Sivertzev-Dobzhansky, N. P. and Dobzhansky, Th.

Deficiency and Duplications For the Gene Bobbed in Drosophila Melanogaster

Genetics, 18: 413.

PDF image facsimile file

1934. — Haldane, J. B. S.

A Mathematical Theory of Natural and Artificial Selection Part X. Some Theorems on Artificial Selection

Genetics, 19: 412-429.

PDF image facsimile file

1934. — Painter, Theophilus S.

A New Method For the Study of Chromosome Aberrations and the Plotting of Chromosome Maps in Drosophila melanogaster.

Genetics, 19: 175-188.

PDF image facsimile file: 915,967 bytes - 14 pages - 2 figures

Now, almost any reference to the genetics of Drosophila includes some illustration of the giant salivary gland chromosomes found in these flies. Although Drosophila had been used effectively since 1910, it was this paper by Painter that first showed the tremendous potential of these chromosomes for cytogenetic research. New discovery often hinges on new methods and this paper is truly a break-through study in genetic methodology.

1934. — Painter, Theophilus S.

The Morphology of the X Chromosome in Salivary Glands of Drosophila melanogaster and a New Type of Chromosome Map for this Element.

Genetics, 19: 448-469.

PDF image facsimile file: 1,519,775 bytes - 22 pages - 2 figures

In this paper, Painter follows up on his earlier publication describing Drosophila giant salivary-gland chromosomes and here shows how genetics maps, obtained from crossing studies, can be placed on a morphological map obtained from cytological studies.

1934. — Schultz, Jack, and Dobzhansky, Th.

The Relation of a Dominant Eye Color in Drosophila Melanogaster to the Associated Chromosome Rearrangement

Genetics, 19: 344-364.

PDF image facsimile file

1934. — Wright, Sewall

An Analysis of Variability in Number of Digits in an Inbred Strain of Guinea Pigs

Genetics, 19: 506-536.

PDF image facsimile file

1934. — Wright, Sewall

On the Genetics of Subnormal Development of the Head (otocephaly) in the Guinea Pig

Genetics, 19: 471-505.

PDF image facsimile file

1934. — Wright, Sewall

The Results of Crosses Between Inbred Strains of Guinea Pigs, Differing in Number of Digits

Genetics, 19: 537-551.

PDF image facsimile file

1935. — Beadle, G. W. and Emerson, Sterling

Further Studies of Crossing Over in Attached-x Chromosomes of Drosophila Melanogaster

Genetics, 20: 192-206.

PDF image facsimile file

1935. — Brink, R. A. and Cooper, D. C.

A Proof That Crossing Over Involves an Exchange of Segments Between Homologous Chromosomes

Genetics, 20: 22-35.

PDF image facsimile file

1935. — Creighton, Harriet B., and McClintock, Barbara.

A correlation of cytological and genetical crossing-over in Zea mays. A Corroboration.

PNAS, 21:148-150.

PDF image facsimile file: 3 pages - no figures

Although Creighton and McClintock's 1931 paper — A correlation of cytological and genetical crossing-over in Zea mays. — had provided data in support of the notion that cytological crossing-over occurs and that it is accompanied by genetical crossing-over, some had criticized the relatively few data points in the paper. In this 1935 paper, the authors acknowledge the criticism, then explain why they will, in this paper, be sharing some additional corroborative data with little additional commentary:

There has recently been some skepticism expressed (Brink and Cooper, 1935) as to the value of the studies on the correlation of cytological and genetical crossing-over in maize published by Creighton and McClintock (1931) because of the fewness of the data. Since the paper by Stern (1931) dealing with Drosophila and having much more extensive data appeared at practically the same time and yielded the same conclusions, the authors felt it unnecessary to add to the ever-increasing amount of published work merely to record more evidence of the same nature without supplying anything essentially new or advancing. Therefore, confirmatory data which have accumulated since the time the joint paper mentioned above was published have not been considered for a separate publication. However, we now feel forced to add more data merely to counteract any suspicion that the evidence previously presented constituted insufficient proof. This will be done in as brief a form as possible, since a discussion of the method has been given in the paper mentioned above.

For additional commentary on Creighton and McClintock's important work, see Edward Coe and Lee B. Kass (2005) Proof of physical exchange of genes on the chromosomes. Proceedings of the National Academy of Sciences, USA. 102:6641-6646.

1935. — Dobzhansky, Th.

Drosophila Miranda, a New Species

Genetics, 20: 377-391.

PDF image facsimile file