Frank A. Stromsten 



473 



in Fig. 6 is a new formation. The rest is the original path of the 

 11 mm. stage. The outer portion of tlie original path (partly hidden in 

 Fig. 6 by the part marked X) is still retained as a tributary of the 

 hepatic umbilical and is later in fonii a part of the left hepatic revehent 

 rein of the adult. 



The vmhitiral veitis join the mesenteric portal vein and lose their con- 

 nection with the common hepatic. Completion of the anlage of the left 

 hepatic revehent vein. Emhrijo of 13 mm. — In the 13 mm. stage, the 

 umbilical veins undergo a still further shifting mediad. Just eaudad 



CAVAL MESENTERY 

 POSTCAVA 



RIGHT HEPATIC- 



PORTAL VEINA^ 

 OF BOJANUS 



VENTRAL LIGAMENT 



EfiTEBRAL VEIN 



POSTCARDINAL 

 MESONEPHROS 



STOMACH 

 iL_ GASTRIC VEIN 



LEFT UMBILICAL 



Fig. 9. Cross section of a 13 mm. embryo of Kinosternon pennsylvanicum 

 through the level where the postcava enters the liver, showing the union of 

 the left umbilical and gastric vein to form the first anlage of the portal vein 

 of Bojanus. 



of the pericardial cavity the right umbilical vein sends a large branch to 

 the mid-line of the ventral body wall, where it receives a small branch 

 from the left umbilical vein (Fig. 8). The median vein formed by the 

 union of these two branches enters the liver through the primary ventral 

 ligament and then immediately divides into two branches. The left 

 branch passes directly dorsad to open into the mesenteric portal, while 

 the right branch soon becomes lost in the hepatic network. 



This short median vein of the primary ventral ligament corresponds 

 in position to the " veine mediane " described in birds by Brouha, 98. 

 It does not, however, arise as an independent vessel in the ventral body- 



