MR. A. HANCOCK ON THE ANATOMY OF DORIDOPSIS. 199 
then sent to the anterior portion of the liver, which it penetrates along with the œso- 
phagus, and seems to go to supply the stomach. The aorta then continues to stretch 
forward until it reaches a peculiar ductless gland (Pl. XV. figs. 1i & 2h) that lies a little 
behind the nervous centres, and which in Doris we have supposed to be analogous to 
some of the vascular glands in the Vertebrata, when it gives off other two branches, one 
to the right, the other to the left; that to the right passes diagonally backwards and 
goes to the reproductive organs at the side of the body, the other enters the blood-gland 
already mentioned. The aorta, still continuing to advance, distributes a branch to the 
posterior or enlarged portion of the proboscis, which branch also supplies a twig to the 
nervous collar. Tt then bends downwards, and sinks into the anterior portion of the foot. 
The blood thus distributed to the various organs, with the exception of that sent to 
the liver-mass, must be supposed to extravasate, after escaping from the various arterial 
ramifications, into the numerous lacunary spaces amidst the tissues, and thus to find its 
way into the great visceral cavity. It will then pass into the skin through various 
apertures provided for the purpose, and, streaming through the spongy tissue of which the 
skin is mainly composed, will reach the great lateral sinuses or veins which terminate 
(Pl. XVI. fig. 4gg & Pl. XVIII. fig. 5dd) one at each side of the auricle. 
The blood that goes to supply the liver and ovary is the only portion of the circulating 
fluid that reaches the specialized respiratory organs; and here, as in Doris, it is col- 
lected by the aid of numerous venous branches into a common hepatico-branchial trunk 
UT XVII fig. 5e), which passes backwards along the median dorsal line of the liver; 
and on reaehing the point where that viscus bifurcates, it turns upwards and opens on the 
central line into the anterior limb of an inner venous or afferent branchial channel (f) 
Which is of a lunate form, with the convexity forward, and the horns passing backwards 
close round each side of the anal nipple. The branchial arteries (y) open into this 
channel, and, passing up the inner surface of the branchial plumes, communicate through 
the leaflets with the branchial veins (4) which run down the opposite or outer side of the 
plumes. These branchial veins debouch, on the other hand, into an outer arterial or 
efferent branchial channel (k), which is likewise of a lunate form, and opens forward 
through the convex margin into the posterior lateral angles of the auricle by two wide, 
short branchio-cardiac veins (ll, and Pl. XVI. fig. 454), one a little on either side of 
the median line. 
Thus the blood that circulates in the liver-mass, and passes through the special respi- 
ratory organs, is mingled with that from the other viscera, which has been returned to 
the auricle) after having been only imperfectly aérated on its course through the dorsal 
envelope) by the two great lateral venous trunks or sinuses before described. 
rom the above description it is evident that the anatomy of the circulatory and 
„ Pratory organs in Doridopsis and Doris is very similar, the only discrepancies being, 
that while in the former there are two branchio-cardiac vessels, only one is described in 
the latter; and that the afferent and efferent branchial channels are lunate, instead of 
Cireular as they are stated to be in Doris. I have reason, however, to believe 
t, when these parts are re-examined in the latter animal, these differences will be 
found to disappear. | 
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