4G6 



Anatomy auJ Development of Veins of Chelonia 



when the ventral anastomosis is destroyed it opens into the right omphalo- 

 mesenteric vein. During further development, as we shall see, it comes 

 to connect with the mesenteric portal vein. Finally, the left umbilical 

 vein unites with the gastric vein and their common trunk forms the 

 portal vein of Bojanus. In the meantime the twisting of the stomach 

 brings the gastric vein to lie on the lesser curvature of that organ. 



In the 10 mm. stage, we find the first definite indications of a con- 

 nection being formed Ijctween the right hepatic and the right sub- 



SINUS VENOSUS—Bi 



r.'ESENTERIC PORTAL 



VENOUS RING 

 OMPHALOMESENTERIC 



VENTRAL ANASTOMOSIS 

 ( POSTERIOR ) 



Fig. 4. Frontal reconstruction of the liver veins of a 10 mm. embryo of 

 Kinosternon pennsylvanicum. Ventral view. 



cardinal vein (not shown in Fig. 4). A small vein is formed in the 

 ventral border of the caval mesentery which extends from the right 

 subcardinal vein to the dorsal border of the liver where it apparently 

 breaks up into a number of finer vessels. Whether these make connec- 

 tions with the liver or not, it is impossible to determine with certainty. 

 The omplialo-Diesenteric veins of an emhryo of ahout 11 nun. — Fig. 5 

 is a reconstruction of the liver veins of this stage. For sake of clearness 

 the smaller branches and the sinusoids are omitted. The posterior ring 



