RENAL ORGAN IN THE NUDIBRANCHIATE MOLLUSCA. 515 
passing from the renal into the pericardial chamber. The valvular nature of the passage 
is still more obvious in those species which have the apex of the vesicle prolonged into a 
tube, as in D. tuberculata. Here this tubular passage is related to the renal chamber 
exactly as the ureters are to the bladder in the higher animals. 
Having now completed our examination of the renal organ in a few British Dorides; 
we may safely conclude that in these animals it is composed of two principal parts, 
namely the pericardial chamber and the renal chamber proper, which are brought intó 
communication by the agency of a third part, the pyriform vesicle, with or without its 
tubular prolongation. We shall now endeavour to ascertain how far these parts are 
modified in the different Nudibranchiate forms, using chiefly in our examination the 
exotie species before alluded to. 
In Doridopsis, a genus of a new family which we have recently established* for the 
reception of certain Doris-like mollusks with suctorial, proboscidiform mouths destitute 
of any armature whatever, the renal organ does not present any very striking modifi- 
cation. 
The renal chamber proper (Pl. LV. figs. 1 & 2) in this genus occupies the usual posi- 
tion on the dorsal surface of the liver; it is of an irregular form, is rather wide, but 
does not branch over that viscus as it does in Doris tuberculata. A few small branches, 
however, apparently penetrate its substance. I have not detected the vascular network 
in the walls of the chamber, nor the glandular matter lining the interior: but these 
features can be observed only under favourable circumstances ; they may therefore exist, 
„though they have hitherto escaped detection. 
The pyriform vesicle is unusually large, firm, and well developed. The narrow extre- 
mity, which lies within the renal chamber, and is adherent to its floor, ends abruptly a 
little in advance of the external opening, and is perforated. The perforation is large, and 
is placed at the junction of the lower wall of the vesicle and the floor of the chamber. 
The upper, overhanging wall of the vesicle will consequently act as a valve, as it does in 
D. pilosa, and prevent any fluid from passing out of the renal chamber into the vesicle 
and consequently into the pericardium. The laminsz in the interior of the vesicle 
(Pl. LV. fig. 3) are well developed, and extend the whole length of the organ; they are 
delicately pinnate. 
The walls of the pericardial chamber are thicker than usual, and the lining membrane 
is raised along the anterior margin of the roof into numerous longitudinal folds, which 
in some of the species extend nearly half the length of the organ backward. They are of 
an opake yellow colour, and have a glandular appearance. 
The renal organ in Tritonia Hombergii exhibits no important modification. The small 
external opening is placed on the right side of the animal, directly above the anal nipple, 
and leads by a short tube, scarcely longer than the thickness of the skin through which 
it penetrates, into a large irregularly formed renal chamber, that lies beneath the peri- 
cardium, resting upon the anterior portion of the liver. The vesicle connecting the 
pericardial with the renal chamber is placed towards the right side; it is very large, 
being scarcely less than the ventricle when in a contracted state, and is somewhat cylin- 
* Trans. Zool. Soc. vol. v. p. 124. 
