RENAL ORGAN IN THE NUDIBRANCHIATE MOLLUSCA, . 521 
system, nowhere communicating with the vascular organs, and that any water admitted 
into it must remain there. Indeed no water could penetrate further than the renal 
chamber proper; for the passage connecting it with the pericardial chamber is, as we 
have seen, of a valvular nature, and would act as the ureters do in the higher animals 
on there being any pressure of fluid in the renal chamber. This is particularly the case 
where the pyriform vesicle terminates in a tubular prolongation. Now we are aware 
that this chamber is glandular, and that in Bornella and Scyllea it has assumed the 
form of an extensively ramified tubular gland, into which it cannot be supposed that 
water would be admitted from the exterior, any more than it should be into the salivary 
or any other gland opening externally. 
Having now concluded a rather lengthy examination of these complicated organs in 
the Nudibranchiata, the first thing that strikes us is the great resemblance they bear to 
the renal apparatus in the Lamellibranchs. In both, the heart is enclosed within a 
so-called pericardium, which communicates with a glandular organ that opens externally. 
In the Lamellibranch the latter is double, being composed of two lateral glands which 
open through the floor of the pericardium by two distinct orifices placed at the sides in 
front. The glandular organ (or renal chamber proper) in the Nudibranch is single, and 
placed symmetrically on the central line. "This therefore can scarcely correspond to the 
former (the organs of Bojanus), but in the Lamellibranch would seem to be represented, 
in part at least, by the point where these two organs open into each other on the median 
line below the pericardium. Is there, then, anything in the Nudibranch that can be 
considered homologous with the organs of Bojanus? We have seen that the pyriform 
vesicle, with its glandular prolongation, is placed at the right side of the animal, and 
opens on this side through the floor of the pericardium. It is therefore a lateral organ, 
apparently single only on account of a deficiency of symmetrical development. Were 
the left-side vesicle present and placed in communication with the pericardium, at a 
point corresponding to the opening on the right, the arrangement of the parts would be 
so similar to that observed in the Lamellibranch that there could scarcely be any hesita- 
tion in pronouncing the vesicle, with its glandular prolongation, and the organ of Bojanus 
homologous. We might therefore at once assume that the latter is the true repre- 
sentative of the former, differing principally in extent of development, were we not 
warned by the presence of the external outlet of the renal chamber proper, which 
assuredly corresponds to the similar orifice of the right organ of Bojanus. PE 
Now, taking this orifice as one fixed point, and the orifice opening into the pericardial 
chamber as another, it is quite possible, as Professor Rolleston has kindly suggested to 
me, that all the anatomical parts that lie between them, including the renal chamber 
proper and the pyriform vesicle with its glandular prolongation, may correspond homo- 
logically to the right organ of Bojanus—or rather that the renal chamber proper repre- 
sents the right organ of Bojanus, and the pyriform vesicle the constricted passage of 
communication between it and the so-called pericardium 
The principal reason against this conclusion is found in the fact that the renal chamber 
proper is usually placed symmetrically on the median line, and is apparently therefore 
not a lateral organ. In our present state of knowledge, however, it is not easy to deter- 
c — — SS TR. —— o MÀ M 
