RENAL ORGAN IN THE NUDIBRANCHIATE MOLLUSCA. 519 
those of the anterior branch. They can be easily raised by the point of a needle ; so that 
their structure is not difficult of demonstration. The ovarian branches spread out over 
the surface of the masses in numerous dendritie systems, similar to those on the anterior 
mass. These ovarian ramuscules (Pl. LVIII. fig. 3) are much more delicate than those 
of the other viscera, and, unlike them, are closely adherent to the surface of the organ, 
but do not apparently penetrate below the surface. 
The whole of this complicated system of branched tubes is glandular throughout. The 
walls of the branches are minutely folliculated (Pl. LVIII. fig. 4), and lined with a very 
finely granular matter, composed chiefly of granular cells (fig. 5). The trunk tubes are 
also lined with the same substance, which gives to the whole system an opake yellow 
colour; hence the facility with which the minutest ramifications can be traced to their 
terminations. 
The renal organ in Scyllea pelagica is provided with the same curious ramified gland ; 
only it is less complicated in its structure. We originally mistook some of the branches 
of the renal gland in this species for a portion of the gastro-hepatie system*, which does 
not apparently exist in this genus. 
On comparing this ramified gland in Scyllea with that in Bornella, the resemblance is 
so obvious that no doubt can exist as to their homological relation. It is interesting, 
however, to observe how intimately the ramifications of the gland in the former are 
connected with the liver and ovary, though modified in this respect from what obtains in 
the Dorides. In Seyllea the liver is broken up into two portions, and the ovary is 
detached from it in the form of three globular masses. But the vascular system is not 
degraded to the same extent as it is in Bornella: both the hepatic and ovarian masses 
are supplied with arteries; hence the ramifications of the gland maintain, to some extent, 
their connexion with the liver and ovary—particularly with the latter, to which, we have 
seen, the ramifications are closely adherent. 
We have now traced the modifications of the kidney through various forms of the 
Nudibranchiata, and find that in all, however diversified, the organ is divisible into two 
principal portions, namely the pericardial chamber and the renal chamber proper; and 
in addition to these, there is always present the accessory organ the pyriform vesicle. 
The first and last of these, as far as we have examined, exhibit no material modification, 
save that the pyriform vesicle is occasionally prolonged into a glandular tube. The 
renal chamber proper, however, is considerably diversified in the several forms we have 
had before us. In Doridopsis and Tritonia we have seen that it is of a wide, irregular 
form, almost devoid of ramifications. In the Dorides it is still a wide sinus or chamber, 
but more or less branched; and in Plocamophorus it has assumed the character of a 
simple tubular gland; while in Bornella and Scylla it becomes extremely developed, 
pervading nearly all the organs of the body by its numerous ramifications—is. in fact, 
in these two last forms, a diffused gland, varying only in the mode of branching : In 
Bornella the branches have a bilateral symmetry, the centre tube being wide; in Scyllea 
there is no apparent order in their distribution, and they are tubular throughout, with 
the trunk or stem only proportionately larger than the rest. | 
* Monograph of the British Nudibranchiate Mollusca, Fam. 2, pl. 5. e. 
