XVI 



49. Gastrnla of Chick 



50,51. Four secondary germ 

 layers . 



52-56. Diagrammatic longitu- 

 dinal and transverse sec- 

 tions through the ideal 

 Primitive Vertebrate 



57, 58. 



61. 



62-69. Diagrammatic trans- 

 verse sections through 

 the most important germ- 

 forms of the ideal Primi- 

 tive Vertebrate 



70. Diagrammatic transverse 



sections through various 

 mammalian germs (ex- 

 plaining the separation 

 of the intestine from the 

 yelk-sac). 



71. Gastrula of Mammal . 



72. Intestinal germ-vesicle of 



Mammal 



73. Transverse section through 



the intestinal germ- 

 vesicle of Mammal 



74. Exoderm-cells of the above 



75. Entoderm-cells of the above 



76. Transverse section through 



germ-area 

 77-81. Intestinal germ-vesicle 



of Babbit 



82, 83. Germ-area of Babbit . 

 81. 



85. 



