THE INCUBATION OF THE EGG 



165 



(more delicate in the inner than in the outer layer), crossing 

 one another in all directions. At the blunt end of the egg 



Fig. 77 



Outer shell membrane (magnified). (Courtesy of Bureau of Chemistry.) 



Fig. 78 





Inner shell membrane (magnified). (Courtesy of Bureau of Chemistry.) 



■«•■ 



the two layers are separated and form an air chamber after 

 the egg is laid."' 



' Lillie's "Development of the Chick." 



