298 Vertebrate Embryology 



the only features of development that will need 

 description here are those connected with the 

 placenta, umbilical cord, etc., with, perhaps, a 

 short description of the decidua and of the 

 development of the external genitalia. 



It will be remembered, in connection with the 

 chick, that, when the head, tail, and lateral folds 

 of the amnion meet over the back of the embryo, 

 the inner layers of the folds fuse together to 

 form the inner or true amnion, while the outer 



Am 



All- 



Ent 



FIG. 94. DIAGRAM OF AN EARLY STAGE OF A PRIMATE EMBRYO. 

 (From Minot.) 



A //, allantois. A nt^ amnion. bs, body stalk. Cho. chorion. Emb, embryo, 

 Ent, entoderm. In, entodermal cavity of embryo. Fr, villi of chorion. K, 

 yolk sac. 



