CONTENTS. XV 



PAGE 



CHAPTER XIV. Digits: Recapitulation . . ' . . .400 



CHAPTER XV. Minor Symmetries: Segments in Appendages 410 



CHAPTER XVI. Radial Series 423 



Coelenterata. PedicellariaB of Echinoderms. Cell-Division. 



CHAPTER XVII. Radial Series: Echinodermata . . .432 



CHAPTER XVIII. Bilateral Series 448 



CHAPTER XIX. Further Illustrations of the Relationship 



between Right and Left Sides . . 463 



CHAPTER XX. Supernumerary Appendages in Secondary 



Symmetry 474 



Introductory. — The Evidence as to Insects. 



CHAPTER XXI. Appendages in Secondary Symmetry . . 525 

 The Evidence as to Crustacea. 



CHAPTER XXII. Duplicity of Appendages in Arthropoda . 539 



CHAPTER XXIII. Secondary Symmetry in Vertebrates. Re- 

 marks on the Significance of Repetition 

 in Secondary Symmetry : Units of Repe- 

 tition 553 



CHAPTER XXIV. Double Monsters 559 



CHAPTER XXV. Concluding Reflexions 567 



INDEX OF SUBJECTS, p. 576. 

 INDEX OF PERSONS, p. 593. 



