496 CHORDATA. 
Fig. 340. —DIAGRAM OF PHASCOLARCTOs (Koala) EMBRYO AND 
ITS F&TAL MEMBRANES. 
(Modified from SEmon). 
Yolk-sac. 
Allantois. 
Yolk-sac. 
Edge of 
Mesoderm. 
Prokalymma. 
Note the yolk-sac villi, but none to the allantois. 
Fig. 341.—DIAGRAM OF HypsopRyMNus (A KANGAROO) EMBRYO 
IN ITS Fara MEMBRANES. (Modified from SEMON.) 
"Yolk-sac 
Yolk-sac. = Villi. 
Prokalymma. Va 
Note the degenerate allantois lying freely. 
