viii CONTENTS. 



CHAPTER V. 



Cleavage (Segmentation) .... ■ ! 



Forms of Cleavage . . . ''" 



Holoblastic Cleavage . . . . . . . • 



Meroblastic Cleavage .... 5 



Some General Features of Cleavage — Cleavage in Mammals . 4 ' 



Practical Suggestions . " 



References for Further Study . • ->4 



CHAPTER VI. 



Germ Layers . . ■ 55 



The Two Primary Germ Layers — Formation of the Gastrula . . 55 



Gastrulation m Amphioxus 55 



Gastrulation in Amphibians ...... 5° 



Gastrulation in Reptiles and Birds . . ■ ° I 



Gastrulation in Mammals .... °7 



Formation of the Middle Germ Layer — Mesoderm . 7 2 



Mesoderm Formation in Amphioxus ... 7 2 



Mesoderm Formation in Amphibians . . 7° 



Mesoderm Formation in Reptiles and Birds 7° 



Mesoderm Formation in Mammals . . • °5 



The Germ Layers in Man ....... &9 



Practical Suggestions . ■ • .96 



References for Further Study . . 97 



CHAPTER VII. 



Fcetal Membranes . . 99 



Fcetal Membranes in Birds and Reptiles ... 99 



The Amnion . . .... ... .... 99 



The Yolk Sac . . 103 



The Allantois ... 106 



The Chorion or Serosa .... . 107 



Fcetal Membranes in Mammals . 107 



Amnion, Chorion, Yolk Sac, Allantois, Umbilical Cord . 108 



Further Development of the Chorion 111 



The Foetal Membranes in Man .. . . 115 



The Amnion .. 115 



The Yolk Sac . . 117 



The Allantois . . 118 



The Chorion and Decidua 119 



The Decidua Parietalis 123 



The Decidua Capsularis 123 



