No. 462.] LATERAL VEIN OF SKATE. 363 
frequent anastomoses, it was really a part, and could be traced 
forward to the cardinal sinus, except for one or two interruptions 
where it completely lost itself by branching into the network. 
If the relatively short gaps in the continuity of this fine vessel 
were filled in and if the continuous vein thus formed should 
become nearly as large as the largest part of the lateral vein, 
the result would be the ilio-haemorrhoidal vein described by 
Parker. The condition just described suggests the presence of 
either an incipient or a rudimentary “ilio-haemorrhoidal " con- 
nection between lateral vein and cardinal sinus. An examina- 
tion of embryonic stages might yield further information. 
The direct connection existing in one case (IV, p. 355) between 
the renal portal system and the lateral vein is due apparently to 
the anastomosis of a parietal factor of the renal portal system 
and one of the parietal branches of the lateral vein. Normally 
these two sets of veins on the dorsal wall of the abdominal 
cavity come into close relation at their initial ends. This 
unusual relation of the lateral vein to the renal portal system is 
of no great importance in itself, but it is suggestive in connec- 
tion with the theory that the lateral veins of elasmobranchs 
are represented in higher vertebrates by the abdominal vein. 
Just as the two lateral veins in the elasmobranch collect the 
blood from the walls of the cloaca and from the pelvic fins, so, 
in the urodele amphibian, the abdominal vein receives the veins 
from the urinary bladder (which is a derivative of the cloaca), 
and the two posterior components of the abdominal vein receive 
the veins from the hind legs. The chief difference is that, in 
the elasmobranch, the lateral system has no direct connection 
with the renal portal system, while in the amphibian each ot the 
two posterior components of the abdominal vein is directly 
connected with the corresponding afferent renal portal vein. 
Development, as is well known, affords some evidence in favor 
of the homology. In consequence of the slight abnormality 
described above, there occurs in the veins on one side of the 
body in the kidney region of a skate an arrangement similar in 
all essential respects to that in amphibians. Such an anasto- 
mosis of a lateral and a renal portal component occurring on 
both sides of an elasmobranch and in the posterior region of the 
