I0O 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 Ophzodon is the left gastric vein 
(Pl. I, figs. r 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 zz¢terlobular veins (fig. 11, I.Lob.V.), 
which break up into venous capillaries, that reunite in forming 
the central or intralobular veins, from which the sublobular 
veins (fig. 11, S.Lob.V.) have their origin. The latter vessels 
are the radicals, which by uniting, form the 2 hepatic veins 
(fig. 11, R. and L.Hep.V.); which come from the right and 
left lobes respectively, and terminate in a hepatic senus 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 Sedastodes both 
portals terminate in a common portal. In Hexagrammos the 
