io6 Vertebrate Embryology 



while the area pellucida soon becomes oval and 

 then pyriform in outline (Fig. 46, ar. pi). 



FIG. 37. (After Foster and Balfour.) 



"Fig. 37, A to N) forms a series of purely diagrammatic 

 representations, introduced to facilitate the comprehen- 

 sion of the manner in which the body of the embryo is 

 formed, and of the various relations of the yolk-sac, 

 amnion, and allantois. 



" In all vt is the vitelline membrane, placed, for con- 

 venience sake, at some distance from its contents, and 

 represented as persisting in the later stages; in the actual 

 egg it is in direct contact with the blastoderm (or yolk), 



