Fig. 136. — Circulation in the embryo and yolk-sac of an embryo of about 

 40 s, showing the later development of the lateral and intermediate vitel- 

 line veins. Reduction of vena terminalis (marginal vein). Almost com- 

 plete atrophy of the right anterior vein. Injected. (After Popoff.) 

 1, Marginal vein. 2 r, 21, Right and left anterior vitelline veins. 3, 

 Arch of aorta. 4, Left posterior "^ cardinal vein. 5 r, 51, Right and 

 left omphalomesenteric veins. 6, Aorta. 6 a, Left dorsal aorta. 7, 

 Vitelline artery. 8, Posterior vitelline vein. 9, Vascular network in the 

 allantois. 



