Front Matter
  I Arrangement of Evidence
  II Segments of Arthropoda
  III Vertebrae and Ribs
  IV Spinal Nerves
  V Variations in Arthropoda
  VI Chaetopoda, Hirudinea, and Cestoda
  VII Branchial Openings of Chordata and Structures in Connection with Them
  VIII Mammae
  IX Teeth
  X Teeth - Recapitulation
  XI Miscellaneous Examples
  XII Colour Markings
  XIII Minor Symmetries: Digits
  XIV Digits: Recapitulation
  XV Minor Symmetries: Segments in Appendages
  XVI Radial Series
  XVII Radial Series: Echinodermata
  XVIII Bilateral Series
  XIX Further Illustrations of the Relationship Between the Right and Left Sides
  XX Supernumerary Appendages in Secondary Symmetry
  XXI Appendages in Secondary Symmetry
  XXII Duplicity of Appendages in Arthropoda
  XXIII Secondary Symmetry in Vertebrates
  XXIV Double Monsters
  XV Concluding Reflections