Parxer.—Anatomy and Embryology of Seymnus lichia. — — 995 
8. Circulatory organs. 
The heart is comparatively small, not more than half the size of that of 
a porbeagle (Lamna cornubica), a few inches longer than the specimen under 
consideration; this is probably correlated with the small size of the pec- 
toral fins. Owing to various unfavourable cireumstances—the chief of 
which was the necessity of preserving the skin uninjured for stuffing—I was 
unable to make a thorough examination of the arteries and veins, and have 
therefore but few observations to record. 
The blood-supply of the alimentary canal presents some points of in- 
terest. Asa general rule the splanchnic arteries consist of two of about 
equal size, the coeliac and the anterior mesenteric springing close together 
from the dorsal aorta and supplying between them the greater part of the 
canal as well as the liver, pancreas, and spleen, and of a small posterior 
mesenteric supplying the rectum. 
In Scymnus, on the other hand, there is only a single main artery, the 
celiac (figs. 2 and 8, c«.a), which sends off a hepatic branch, and runs 
backwards along the right side of the stomach, parallel to the bile-duct and 
portal vein, supplying the left side of the stomach as it goes; it then passes 
to the dorsal side of the bursa Entiana, and curves round the latter to reach 
the ventral aspect of the intestine ; forming then the duodenal artery (du. a) 
which takes a spiral course round the ventral and left sides of the gut, send- 
ing off transverse branches to its walls, as well as the intra-intestinal 
artery presently to be described. The cceliac also gives off, near the 
pylorus, a small left gastric artery (g. a), which curves round the posterior 
border of the stomach, and then passes straight forward along its left side. 
The rest of the alimentary canal is supplied by no less than three mesen- 
terie arteries, an anterior (fig. 8, a.m. a), a middle (m. m. a), and a posterior 
(p.m. a); all are small arteries proceeding straight from the dorsal aorta to 
the right side of the intestine, and forming between them a longitudinal 
vessel, which runs parallel to the mesenteric vein (m. v), sends off transverse 
branches to the right side of the intestine, and takes altogether a spiral 
course, so that its distal end comes to lie on the ventral wall of the gut 
(fig. 2, p. m. a). The anterior mesenteric, which is the largest of the three, 
gives off a lieno-gastrie artery (l. g.a), which gives branches to the spleen 
and is continued up the left side of the stomach. 
The blood is returned from the intestine by two veins, the duodenal 
(du.v) and the mesenteric (m. v), which pass forward with a turn to the 
right and unite with one another close to the pylorus to form the portal 
vein (fig. 8, p. v) : the duodenal runs alongside the artery of the same name 
(du. a), the mesenteric alongside the longitudinal branches of the mesenteric 
arteries. The duodenal vein receives transverse veins from the intestinal 
