BLOOD-VASCULAR SYSTEM OF THE LORICATI 10g 
Mes.V.). This vessel arises from 2 good sized branches 
designated as Y and Z (see fig. 1). Branch Z which is strictly 
a gastric vein, takes its origin from several branches coming 
from the posterior or cardiac end of the stomach; one of which 
anastomoses with the right gastric vein; and 2 other branches 
anastomose with branches of the left gastric and posterior gas- 
tric veins. Thecourse of branch Z is dorso-caudad ; passing to 
the left of the intestine and its vessels, it unites with branch Y 
directly below the reproductive organs. Branch Y, which is 
distinctly an intestinal vein, drains the posterior end of the 
intestine, and usually anastomoses with intestinal vein ,,); pass- 
ing caudad it joins branch Z in forming the main posterior gas- 
tric stem, which passes between the reproductive organs, with- 
out receiving any branches, penetrates the posterior ventral 
surface of the kidney, and passing to the left of the right 
cardinal empties into the renal portal vein. It would be possible 
for the blood in the posterior mesenteric to flow in either direc- 
tion, but it is probable that the least resistance is toward the 
kidney. 
After receiving the posterior mesenteric vein the caudal or 
renal portal vein bifurcates into a r7ght and a left renal portal 
ven or vena renalis advehens (figs. 1 and 10; Ren.P.V.). 
These trunks run cephalad for some little distance through the 
dorso-lateral part of the kidney, and gradually decrease in 
caliber by giving off numerous ventral branches, the aferent 
renal veins or venae renales advehentes (figs. 1 and 10, 
A.Ren.V.). These vessels break up into rather coarse venous 
capillaries near the lateral surface of the kidney, and become 
collected ventrad and mesad by the small efferent renal veins 
or venae renales revehentes (figs. 1 and 10; E-Ren\. Vs). oe 
cross section through an injected kidney hardened in formalin 
shows us that these vessels, many of which are visible from the 
ventral side of the kidney, empty into the right cardinal from 
every direction. 
(6) The right cardinal vein (Pl. I, figs. 1, 5 and 10; 
R.Car.V.), which is the principal cardinal has its source 
mainly from the efferent renal veins; it arises in the extreme 
caudal end of the kidney, below the caudal vein, and passes 
