CONTENTS. XV 



PAGE 



CHAPTER XIV. DIGITS: RECAPITULATION 400 



CHAPTER XV. MINOR SYMMETRIES: SEGMENTS IN APPENDAGES 410 



CHAPTER XVI. RADIAL SERIES 423 



Ccelenterata. Pedicellarise of Echiuoclerms. 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. 



