450 



Helen Williston Smith. 



chiefly into the umbilical vein. The lower part of the membrana re- 

 uniens (MR) as high as the point where the umbilical vein enters the 

 liver, is seen to be full of veins. These rise from a fine network 

 of capillaries which is fed by the segmental arteries and extends 



Fig. 3. — Embryo 8 mm. loug. Enlarged 14 times. 



Only the superficial vessels are shown. 



Vlf. linguo-facial vein; 8R. sinus reuniens ; Pars sup. V.u, superficial 

 portion of umbilical vein ; MR, membrana reuniens ; V.ud, right umbilical 

 vein ; V.ca, anterior cai'dinal vein ; V.cp, posterior cardinal vein. 



in a crescent shape, with the concavity directed ventrally between 

 the two limb buds. In the lower portion, this network is entirely 

 irregular, but higher up it forms a more or less connected plexus 

 which passes partly into another plexus extending ventrally to the 



