172 MOLLUSCA. 
proceeds to the liver on the left. The larger branch is again 
divided, the smaller branch proceeding to the stomach. The 
largest trunk that remains, before it leaves the pericardium, 
has two singular bodies attached to it, consisting of com- 
paratively large vessels, opening from this aortic branch. 
The use of these glands is unknown. The organs of gener- 
ation likewise exhibit some remarkable peculiarities. The 
ovarium is situate in the posterior part of the abdomen. The 
oviduct is tortuous in its course, passes along the surface of 
the testicle, and, after uniting with a clavate appendage, 
opens into acommon canal. The testicle is firm, apparently 
homogeneous in its texture, of a yellow colour, with spiral 
ridges on its surface. The vas deferens arises from a com- 
plex, glandular body, and unites with the common canal. 
This common duct, before it reaches the external orifice, 
receives the contents of the pedunculated vesicle, and has 
attached to it a botryoidal, glandular organ, the use of which 
is unknown, but which some suppose to be employed to se- 
crete an acrid liquor regarded as venemous. It is obvious 
from this structure, that the seminal fluid and eggs must 
come in contact in the common canal, and at the single ori- 
fice, provided they are both ejected at the same time. From 
the orifice to the right fore-feeler there is a sulcus, leading 
to the pore containing the retractile penis. This organ, 
like those of the other mollusca, is solid. It terminates in 
a small filament. The external groove is the only connec- 
tion between it and the other sexual-organs. 
There is a peculiar secretion of a purple fluid which here 
deserves to be recorded. It issues from a spongy texture, 
underneath the free side of the dorsal plate. Connected 
with this cellular reservoir is a glandular body of a consider- 
able size, which is supposed to secrete the coloured fluid. 
