Frank A. Stromsten 483 



In general the development of the veins of the hepatic and renal portal 

 systems is the same in turtles as in lizards and snakes. The more im- 

 portant differences are noted below : 



Turtles differ from lizards as follows: 



1. The left umbilical vein loses its t-onnection with the sinus venosus 

 before the posterior venous ring around the intestine is formed. 



2. Both umbilical veins enter the liver, and both persist, in part, to 

 form the pre-umbilical portion of the abdominals of the adult. 



3. The subcardinals do not form a venous ring around the origin of 

 the omphalo-mesenteric artery; hence, the right subcardinal, instead of 

 an unpaired stem in front of the origin of this artery, joins the right 

 hepatic vein to form the postcava. 



4. The postcava is a single vessel, in the adult, back as far as the cranial 

 ends of the permanent kidneys, where it bifurcates into two branches 

 which receive the suprarenal, renal, and spermatic veins. 



5. The posterior vertebral veins are developed dorsal to the anlages of 

 the ribs. 



6. The postcardinals are not broken up in the early stages into broad 

 blood sinuses by the mesonephric tubules as they are in lizards, but 

 retain their integrity as independent vessels along their entire length. 



Turtles differ from snakes as follows: 



1. The right emphalo-mesenteric vein is, at first, smaller than the left. 



2. The right umbilical vein does not enter the liver until after the 

 left has done so. 



3. Both umbilicals eventually open into the portals. 



4. The postcava does not open into the common hepatic vein formed 

 by the union of the right umbilical with the right hepatic, but into the 

 right hepatic before the latter joins the common hepatic. 



5. The postcava, as stated above, is unpaired. 



6. The postcardinals are not, at first, connected with the caudal, but 

 a connection is later and secondarily formed. 



7. The posterior vertebral veins are formed above the rib anlages, and 

 persist in the adult. 



