524 MR. A. HANCOCK ON THE STRUCTURE AND HOMOLOGIES OF THE 
passage of communication between the two chambers, and it is also placed towards the 
right side, while in the Cuttlefish there are two similar lateral passages symmetrically 
placed. In the Octopod, too, as just stated, the renal chamber is divided on the median 
line into two lateral halves. Much of this bilateral symmetry we have seen to exist in 
the Lamellibranchs, in which there are two external openings and two passages of com- 
munication between the chambers. Its absence, however, in the Gasteropodous Nudi- 
branch is what might be looked for, and in no way militates against the homology of 
the parts. 
But the presence of this symmetry in the Lamellibranchs and Cephalopods has never- 
theless a certain bearing upon the relation of these organs in the Nudibranchs. It seems, 
in fact, to favour the opinion previously alluded to as expressed by Professor Rolleston 
on this subject; for if we assume that the two lateral halves of the renal chamber in the 
Octopod, with their two passages of communication and two external outlets, represent 
the two organs of Bojanus, it would appear probable that the renal chamber of the 
Nudibranch is the homologue of the right organ of Bojanus, and that the pyriform 
vesicle is nothing more than the right passage of communication between the two renal 
chambers, whether of the Lamellibranch or of the Cephalopod. 
In the next place, the relative situation of the renal chamber to the other viscera is 
very dissimilar in the Nudibranchs to that in the Cephalopods. This is very striking at 
first sight, but on a little consideration any doubt as to the homology of the organs on 
this score is readily removed. To judge fairly in this matter we must imagine what 
would take place on transforming the Nudibranch into the Cephalopod. To enable us 
to do so, we must place the former with its head downwards, and suppose the foot deve- 
loped round the oral orifice (Pl. LIX. figs. 1 & 2). The intestine must then be bent 
forward so as to bring the anal nipple towards the head, earrying along with it the renal 
chamber proper and its external opening to the under or opposite side of the liver. And 
now, if the pericardial chamber be developed upward and backward, we shall see that the 
two renal chambers have assumed their Cephalopodous positions. Their contents, how- 
ever, are very different; but this is apparently not of much consequence, for in the 
Cephalopods themselves they do not always contain the same organs. 
In the Octopodide the genital chamber holds only the ovary or testis, according to the 
sex, while the same chamber in the Loliginide usually contains, in addition to these 
organs, as before pointed out, the stomach, cecum, and branchial hearts, with their 
appendages; though in Sepia one-half of the stomach and the whole of the csecum are 
excluded. Again, in the Octopodide the renal chamber or pseudoperieardium has occa- 
sionally protruding into it the upper or convoluted portion of the intestine, and always 
the vene caver with their renalappendages. In the Loliginide this chamber invariably 
contains, in addition to the vene cave and their appendages, the hepatic ducts with 
their appended pancreatic glands, and in Ommastrophes, as well as these, the lower por- 
tion of the intestine and the greater part of the ink-bag, while in Sepia it likewise 
holds half the stomach and the whole of the spiral caecum. 
| It apparently therefore depends in a great measure upon the extent and direction of 
the development of these chambers what organs they enclose. Consequently we ought 
