m-e/n 



sv 



FIG. 159. The yolk of a Hen's egg at, A, the thirty-sixth hour from the beginning of 

 incubation ; B, the third day ; C, the end of the fifth day ; and D, the end of 

 the ninth day (about nat. size). (Compare Fig. 158.) 



ad. area pellucida ; an. inner or " true " amnion ; ak. area opaca ; av. area vasculosa 

 (in C its outer margin) ; az. outer or " false " amnion (serous membrane), 

 together with the vitelline membrane ; em. embryo ; km. hyomandibular cleft ; 

 sh. egg-shell ; sm. vitelline membrane (in C, shell membrane) ; sv. air-chamber ; 

 ta. allantois ; wa. white or albumen ; y. ys. yolk-sac. (From Marshall.) 

 598 



