198 MR. A. HANCOCK ON THE ANATOMY OF DORIDOPSIS. 
sac or enlargement corresponds to the dilated portion of the oviduct in the former Species, 
The duct shortly afterwards bends suddenly upon itself, and receives a minute tube (d) 
from the inner extremity of the dilated portion of the vas deferens proper, and then, 
turning to the right (£), after a short course, dips (7) into the mucous gland at the point 
where the latter is united to the female channel. 
The mucous gland (y) is lunate, with the convexity towards the right side of the body; 
it is pretty uniformly of a pale yellowish hue. The posterior portion is made up of a 
densely convoluted tube, which at the extremity of the organ is coarse, but very minute 
next the female channel. The anterior extremity is apparently strongly and irregularly 
laminated or folded in the interior. The female channel (e) is much longer than usual, 
and tapers towards the external outlet. It opens, apparently, into the centre of the 
mucous gland. The gland (f), in connexion with the external outlet, is considerably 
larger than it is in the previously described species, and its walls are more strongly 
follieulated. . 
The vagina (m), or tube leading from the exterior to the spermatheca, is exceedingly 
slender. The outer extremity, though somewhat enlarged, corresponds in size to the 
diminutive penis. This tube is longer than that in the former species, and so is the tube 
which goes from the spermatheca to the oviduct; and the latter tube is a little swelled (4) 
just before it receives the duct from the accessory spermatheca. The two sperma- 
thecæ (x, p) are nearly of a size; but in other respects they resemble those previously 
described. The accessory spermatheca was found crammed full with spermatozoa in 
bundles. 
Circulatory and Respiratory Systems.—The blood-eireulation and respiration appear 
to be much in the same condition as they are in the Dorides. The heart is placed far 
behind upon the dorsal surface of the liver, immediately beneath the skin of the back. 
It occupies a well-defined membranous pouch, the so-called pericardium, which is large 
in these animals, and is as wide as the visceral mass upon which it rests. In D. gem- 
macea the walls of this organ (Pl. XV. fig. 17) are rendered unusually opake by the 
eolouring-matter of the peritoneum, which is of a strong brown hue, and which forms 
the outer layer of the pouch. On laying the latter open, the inner or lining membrane 
of the dorsal wall is found to be thrown into folds or plates (Pl. XVI. fig. 40), which 
extend from the anterior margin for some way backward. They are of a pale yellow 
colour, and have somewhat the appearance of being glandular. 
The ventricle (c) is pyriform, with the apex placed forward, and has thick museular 
walls. The auricle, the walls (e) of which are, as usual, thin and delicate, occupies the 
posterior half of the pericardium, and opens in front through the posterior margin of the 
ventricle. The orifice is guarded by two delicate semilunar valves, and the interior of 
the ventricle is well provided with strong carneæ column. The auricle, t00, is, PP 
em with fleshy columns (f); but they are less numerous, and are delieate and thread- 
e. 
= arterial system seems to be as complete as it is in Doris. The aorta (Pl. XV. fig. 
ds issues from the anterior apex of the ventricle, and gives off immediately two = 
trunks, which pass backwards and go to supply the liver and ovary. A small branten 
