CONTENTS 



XI 



VERTEBRATES 



CHAPTER XVII 



Hemichorda 



• • 



PAGE 



. 489 



CHAPTER XVIII 



Urochorda 



• • 



f • 



499 



CHAPTER XIX 



Cephalochorda 



• * 



• t • 



. 515 



CHAPTER XX 



Structure and Development of Vertebrates . .529 



Cyclostomata 



CHAPTER XXI 



. 574 



Fishes 



CHAPTER XXII 



• • 



. 587 



Amphibia 



CHAPTER XXIII 



649 



Reptiles 



CHAPTER XXIV 



. 683 



Birds 



CHAPTER XXV 



725 



Mammals 



CHAPTER XXVI 



. 776 



