No. 462] LATERAL VEIN OF SKATE. 353 
and cardinal sinus by means of minute vessels, if such existed. 
Accordingly we undertook to determine if any connection what- 
ever was to be demonstrated. 
Six fresh skates were secured, four of them being the common 
Raia erinacea and two AR. /evis. Our operations and results 
upon these six animals are described below. In each case the 
caudal vein was injected for the purpose of differentiating the 
renal portal connections. The celloidin injections were made 
with very thin, easily flowing celloidin colored with finely pulver- 
ized carmine or Prussian blue. Careful dissections and draw- 
ings of the injected vessels were made by Mr. Ulrich. 
I. Raia levis: young male. 
1. Renal portal system injected, va the caudal vein, with blue 
celloidin. 
Minute separated masses of the celloidin appeared in the post- 
cardinal veins, apparently having passed through the renal capil- 
laries. A considerable quantity of celloidin from this source 
collected in the cardinal sinus and some of it made its way back 
into the posterior or rectal prolongation of that sinus. 
2. Left lateral vein injected posteriorly with red celloidin. 
The red mass appeared on the walls of the cloaca and rectum 
in a close network of very fine vessels extending forward to, and 
a little beyond, the base of the rectal gland. Small vessels con- 
nected with this network conveyed the celloidin along the 
ventral margin of the mesorectum, in the region of its attach- 
ment to the rectum, apparently into the posterior end of the 
rectal prolongation of the cardinal sinus. Here an interval of 
only three or four millimeters separated the blue and red injec- 
tion masses. 
The dissection of this fish proved that both the red and the 
blue celloidin had entered the rectal prolongation of the cardinal 
sinus. The failure of the two masses actually to meet was 
doubtless caused by the inclusion between them of a quantity of 
gas for which there was no avenue of escape. The lateral vein 
received two trunks from the pelvic fin. The larger one of the 
two emerged from the fin dorsal to the end of the girdle and 
