CONTENTS. 



Hemichorda 



Urochorda 



CePHALOCHORDA 



VERTEBRATES. 

 CHAPTER XVII. 



CHAPTER XVIII. 



CHAPTER XIX. 



CHAPTER XX. 



Structure and Development of Vertebrates 



Cyclostomata . 



Fishes 



Amphibia 



Reptiles 



Birds 



Mammals 



CHAPTER XXI. 



CHAPTER XXII. 



CHAPTER XXIII. 



CHAPTER XXIV. 



CHAPTER XXV. 



CHAPTER XXVI. 



PAGE 

 387 



396 



4 II 



425 



469 



480 



53° 



560 



593 



632 



