lOO ALLEN 



posterior dorsal surface of the bladder and anastomoses with 

 the anterior gall-badder vein, empties into radical a of the left 

 portal. This radical may also receive a similar, but smaller 

 vein from the ventral surface of the bladder. 



An interesting vessel in Ophiodon is the left gastric vein 

 (PI. I, figs. I and 6; L.Gas.V.), since it is not connected with 

 the portal system but terminates directly in the precava. This 

 vein has its origin in 2 branches from the left side of the 

 stomach, on either side of the left gastric artery. The ventral 

 branch is usually the larger ; arising from the extreme posterior 

 end of the stomach, its branches anastomose with those of 

 branch Z of the posterior mesenteric vein. When the anterior 

 portion of the stomach is reached the smaller left gastric branch 

 crosses over the left gastric artery and joins the main stem of 

 the left gastric, and the combined vessel passes forward above 

 the left gastric ramus of the vagus and empties into the precava. 

 Still another small gastric vein arises from the anterior dorsal 

 surface of the stomach and terminates in the precava, above 

 the main left gastric vein. 



As in other vertebrates the intestinal, gastric, and caeca veins 

 arise from capillaries in the connective tissue layer of the crypts 

 and the larger branches run in the muscular layers. Within 

 the liver the terminal branches or radicals of the two portals 

 exhaust themselves in the intej'lobular veins (fig. 11, T.Lob.V.), 

 which break up into venous capillaries, that reunite in forming 

 the central or intralobtilar veins, from which the siihlobular 

 veins (fig. 11, S.Lob.V.) have their origin. The latter vessels 

 are the radicals, which by uniting, form the 2 /lepatic veins 

 (fig. IT, R. and L.Hep.V.); which come from the right and 

 left lobes respectively, and terminate in a Jicpatic sinus that 

 enters the sinus venosus from the rear. In the liver the main 

 trunks of the hepatic system lie beneath those of the portal 

 system. 



As in the arteries, most of the variation of the veins in this 

 group occurs in the viscera. Nevertheless, all of the species 

 examined had a distinct right and left portal, which break up 

 in the right and left lobes respectively. In Sehastodcs both 

 portals terminate in a common portal. In HcxagraDinios the 



