BLOOD-VESSELS OF MUSTELUS ANTAHCTICUS. 
707 
[Dors, intes. V.) and anterior lieno-gastric [Ant. li. gcist. V.) veins, while immediately 
before joining the portal it receives the anterior gastric vein [Ant. gcist. V.). 
The clorsal intestinal vein. 
Mesenteric vein (in Raja and Scymnus), Parker (20-23). 
The remarks made above (p. 693), as to the absence of any close correspondence 
between the splanchnic arteries of different Elasmobranchs, apply equally well to the 
veins. In Raja (21, 23) nearly the whole of the blood from the intestine is returned 
by a large mesenteric vein, lying dorsally and somewhat to the left, this being 
supplemented by small duodenal (ventral intestinal) and intra-intestinal veins ; these, 
together with the splenic and pancreatic veins, unite to form a common trunk which 
is afterwards joined by the gastric veins. The mesenteric vein, from its position, 
evidently answers to the vessel now under consideration in Mustelus. In Scymnus (22) 
the duodenal (ventral intestinal) vein has become as large as the mesenteric (dorsal 
intestinal); the tw T o unite with one another, the mesenteric previously receiving a 
large lieno-gastric vein, and into the common portal vein thus formed the remaining 
gastric veins are discharged. 
In Mustelus the blood is returned from the intestine by no fewer than three veins, 
each as large proportionally as the single mesenteric vein of Raja. Two of these, as 
already seen, unite with one another and with the posterior lieno-gastric ; the third, 
the dorsal intestinal vein now under discussion (Plate 37, figs. L2 and 13, Dors. 
Intest. V.) commences on the ventral or free border of the rectal gland, where it 
anastomoses with the posterior oviducal, spermatic, and cloaca! veins (Plate 34, fig. 3), 
and apparently receives most of the blood from the posterior extremity of the gonad. 
As far as my observations go, I am disposed to consider this relation with the rectal 
gland as constant for the dorsal intestinal vein of Plagiostomes. 
Passing forwards, the dorsal intestinal vein receives transverse factors from the 
walls of the intestine and outer regions of the turns of the spiral valve ; these 
probably anastomose both with those of the corresponding feeders of the ventral 
intestinal and with those of the intra-intestinal vein. 
In the position actually assumed by the intestine in the adult fish the dorsal 
intestinal vein, through a considerable part of its course, lies on the left side, 
the ventral intestinal on the right (Plate 37, fig. 22). But as the former trunk is a 
continuation, forwards, of the line of the rectal gland and mesorectum, i.e. the line 
along which the mesentery, if present, would be attached, it is morphologically dorsal 
in position. 
Arrived at the posterior boundary of the duodenum, or in other words at the 
junction between the first and second turns of the spiral valve, the dorsal intestinal 
vein leaves the wall of the gut (fig. 12), and, still accompanied by the corresponding 
artery, passes dorsalwards, supported by a fold of mesentery, to the posterior 
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