116 Victor E. Emmel. 
the body through an immense blood sinus (vs). As this sinus passes 
through the ischiopodite it is temporarily separated into two channels 
by a connective tissue partition or septum (S). One of these chan- 
nels passes ventrally and the other dorsally, through the breaking 
joint. The two nerves and arteries lie within the septum and 
adjacent connective tissue separating the two venous channels. 
In the course of these two blood channels just as they enter the 
basipodite after having passed through the breaking joint, there 
occur two very interesting valve-like folds of connective tissue. These 
two structures arise in the following manner from the median septum 
separating the blood channels. As the septum extends proximally 
into the basipodite it becomes divided into two plates or folds 
(v', v2) much like the arms of an inverted “Y,” one of the arms 
passing toward the dorsal wall and the other toward the ventral 
wall of the segment. The fold extending toward the dorsal wall is 
somewhat shorter and thicker than the one on the ventral side. 
These two folds do not completely unite with the walls of the basi- 
podite. A part of the border of each fold retains a free edge, which, 
together with the opposing wall of the segment, completely encloses 
the lumen of each blood channel. Beyond (7. e., proximally) these 
folds the two blood channels reunite to form again a common venous 
sinus (vs”). 
While endeavoring to understand the significance of these folds 
as they were first seen in the serial sections, it was suggested that 
they might possibly function as valves for the venous blood channels, 
the valves closing when the limb had been autotomously removed. 
Following up this suggestion, serial sections of specimens which had 
been fixed immediately after the autotomy of the chela, were then 
examined. It was at once evident that the folds in question had 
assumed in these specimens a position different from that observed 
in sections of a chela before the limb had been removed. Each fold 
had now become distended in a distal direction as if caught by an 
outward blood pressure, the result being the complete closure of the 
ruptured end of the two blood channels (Fig. 4, v?). Desiring to 
make a still further test, a number of live lobsters were then obtained 
and the chele autotomously amputated. At first there was a short 
