360 THE AMERICAN NATURALIST: [VoıL. XXXIX. 
Do the veins of the rectal network communicate directly with 
the posterior factors of the hepatic portal system, as stated by 
Hochstetter for Squalus, and as thought probable by Parker ('81) 
for Raza nasuta ? 
Good starch injections of the intestinal veins often result in 
the demonstration of a venous network on the rectum in the 
region of the base of the rectal gland. The network which has 
been demonstrated by injection from the lateral vein often ex- 
tends into the same region. It is improbable that there should 
be two distinct and non-communicating sets of veins in this same 
region of the intestine. In one case (I) the red celloidin passed 
through the venous network on the rectum and appeared in a 
very small vessel which was identified, with a fair degree of cer- 
tainty, as the extreme posterior end of the mesenteric or dorsal 
intestinal vein, the hindmost trunk of the hepatic portal system. 
The failure of the celloidin to flow freely through the network 
into the hepatic portal vessels, granting that the connection 
exists, might well be due to the solidifying of the celloidin in the - 
fine vessels of the network as the result of contact with moisture. 
The senior author has seen injected skates in which a yellow 
starch mass, injected backward into the mesenteric vein, appeared 
actually to meet, in the region of the rectal gland, a blue starch 
mass which had made its way into the rectal network via the 
rectal extension of the cardinal sinus, the two masses clearly 
lying in the same vessels. 
With a view to getting more conclusive evidence as to the 
relation between the rectal network and the hepatic portal sys- 
tem, the senior author secured some fresh skates of the common 
species, A. erinacea (at Woods Hole, Massachusetts, through 
courtesy of officials of the United States Bureau of Fisheries 
and of the Marine Biological Laboratory) and made injections 
in the following way. A fluid consisting for the most part of 
water, but containing a small amount of glycerin and colored 
with finely pulverized insoluble Prussian blue, was injected back- 
ward into one of the lateral veins. The rectal network imme- 
diately became very fully injected and the blue fluid passed 
along the mesorectum into the cardinal sinus, in the manner 
already described. Then a ligature, which had previously been 
