496 



CHORD AT A. 



Fig. 340.— Diagram of Phascolarctos {Koala) Embryo and 

 ITS FcETAL Membranes. 



(Modified from Semon). 



Yolk-sac. 



Allantois, 



Yolk-sac. 



Edge of 

 Mesoderm, 



Amnion. 



Prokalymma. 

 Note the yolk-sac villi, but none to the allantois. 



Fig. 341.— Diagram of Hypsoprymnus (A Kangaroo) Embryo 

 IN its Fcetal Membranes. (Modified from Semon.) 



Amnion. 



Vllantois. 



Yolk-sac. 



Prokalymma. ^ 



Note the degenerate allantois lying freely. 



