472 EMBKYOLOGY OF THE LOWER VERTEBRATES oh. 



vesicle, projecting from the ventral side of the trunk near its hind 



all. am. 



sa 



f° 



coel 

 el 



alh 



spl- 



it 



Fig. 215. — Diagrams illustrating the arrangement of amnion, allantois, etc., in the Fowl. 



(After Lillie, 1908.) 



A, fourth day; B, ninth day. a.c, amniotic cavity; alb, albumen; all, allantoic cavity; all.st, 

 allantoic stalk; am, amnion; coel, coelome ; f.a, false amnionj or serous membrane; sa, seroamniotic 

 isthmus; spl, splanchnopleure ; v.m, vitelline membrane; y t yolk; 1, outer wall of allantois fused 

 with serous membrane ; 2, inner wall of allantois. 



