448 



Helen Williston Smith. 



posterior cardinal (Vcp), but lower down there is a very rich plexus, 

 lying ventral to the anlage of the posterior limb bud, which com- 

 municates freely with a similar plexus on the opposite side of the 



Fig. 2. — Embryo 7 mm. long, in wliicli the injection is complete. The ves- 

 sels in the head are semi-diagrammatic. Enlarged 21 times. 



Y.lf, linguo facial vein; SR, sinus reuniens ; V.nd, right umbilical vein; 

 vein; V.iis, left umbilical vein; A.om, omphalomesenteric artery; Ao, aorta; 

 V.ca, anterior cardinal vein ; V.cj), posterior cardinal vein ; Pars sup. V.u, 

 superficial part of umbilical vein. 



body, and as the figure shows, with its respective umbilical vein. 

 Dorsal to the posterior limb bud the posterior cardinal (Vep) arises 

 from numerous, capillaries which unite to form a vein running along 



