104 



J. Thos. Patterson. 



inner edge of the germ-wall (Fig. XV). Hence, in transverse sec- 

 tions of the majority of blastoderms taken at this time, the entoderm 

 will appear to be an outgrowth from the inner edge of the germ- 

 wall. Fortunately, in not a few blastoderms the union between the 

 invaginated entoderm and the germ-wall does not take place until 

 about the time the egg is laid, and in such deferred cases it is easy 

 to distinguish the lateral edge of the entoderm (Fig. 48), and thus 

 to demonstrate that the gut-entoderm, at least in its lateral parts, 

 does not receive elements from the germ-wall. Can the same be said 



Fig. XV. Reconstruction of a blastoderm taken thirty-eight hours after 

 fertilization. This blastoderm is approximately in the same stage of devel- 

 opment as that of an unincubated hen's egg. x ^^.2. 



of its anterior and posterior parts ? In regard to the former we 

 can answer in the affirmative without hesitation ; for in every blasto- 

 derm taken from the time of midgastrulation until three or four 

 hours after incubation, there is found between the anterior limit 

 of the entoderm and the germ-wall, a portion of the subgerminal 

 cavity in which there are practically no nucleated cells. Indeed, 

 in many blastoderms there are no cells, not even yolk masses (Fig. 



