480 



HENRY F. OSBOHN. 



s.t. 



Diagrams showing the relations of the foetal membranes. — Fig. 1 

 represents the actual relations of the membranes at the middle period in 

 the opossum and the kangaroo. The shaded ring (uL) represents the wall 

 of the uterus in section, showing how the villous area of the subzonal 

 membrane (sz.) is in contact. Fig. 2 shows how in Specimen 2 a portion 

 of the yolk-sac forms an attached villous area beyond the sinus terminalis; 

 the dark villi are those actually observed, the remainder are supposed to 

 have been present when the membranes were complete. The supposed 

 adherence of the allantois ((?/.) to the subzonal membraue is also shown. 

 St. Sinus terminalis. am. Amuior. Va. Vitelline artery and veins. 

 z. Villi of younger specimen, v. Vascular villi of older specimen, the 

 black ones observed, the unshaded ones inferred. 



