200 MR. A. HANCOCK ON THE ANATOMY OF DORIDOPSIS. 
Renal Organ.—This organ is composed of three parts, namely, the Pyriform vesicle, 
the so-called pericardium, and the renal chamber proper, with its external outlet. 
The pyriform vesicle in Doridopsis gemmacea (Pl. XV. fig. 4%) is larger than usual, and 
in some species is nearly half the size of the contracted ventricle. It lies diagonally 
below the posterior portion of the so-called pericardium, the broad end opening through 
the floor of that organ a little behind the margin of the auricle, near to the point where it 
receives the right pallial trunk vein. The orifice (/) is circular, and apparently capable 
of being closed by a sphincter muscle. The other or pointed extremity protrudes into 
a large sac or chamber, the renal chamber proper (g), with membranous walls, that lies 
on the posterior portion of the liver directly above the branchio-hepatie vein. The point 
is perforated (m) ; and as the under surface of the vesicle is cemented, as it were, to the 
floor of the chamber, the upper wall of the former overhangs the orifice, and acts asa 
valve to prevent the return of fluid through the vesicle into the pericardial chamber. 
The vesicle itself is of a pale yellow colour, and has firm muscular walls ; and the interior 
is lined throughout with numerous longitudinal pinnate lamine. 
From the connexion of the parts, it is clear enough that the so-called pericardium is 
really a portion of the renal organ. The former is rather larger than usual, and the 
inner surface of the dorsal wall, as we have already seen, is laminated in a peculiar manner 
at the anterior margin. The laminæ (Pl. XVI. fig. 42), which are of an opake yellow 
colour, are thick and close-set at the margin, but die gradually out as they extend back- 
wards. They have a gland-like appearance, though of a firm texture. 
The renal chamber proper (Pl. XV. fig. 4 g) is of an irregular form, somewhat pointed in 
front, and widening backwards. The dorsal wall is delicate and membranous, but quite 
distinct; the floor, however, is confounded with the capsule of the liver-mass, and is 
scarcely, if at all, demonstrable. A few small openings (/) in the floor show that the 
chamber is not simple, but sends branches into the liver. The wall of the widened 
posterior extremity is adherent to the dorsal skin of the animal at the base of the bran- 
chial crown; and here the chamber opens externally through a puncture (j) situated 
close to the right side, and in front of the anal nipple. | 
The extensive vascular ramifications in the walls of the renal chamber proper in Doris 
have not been observed in Doridopsis ; neither has the glandular lining of the organ 
been seen. It is only under favourable circumstances that these characters can be 
detected; and many specimens may be opened before one is found that exhibits them. 
The renal organ does not vary much in the few species that have been examined. The 
pyriform vesicle (PL XVI. fig. 17) in D. nigra is large, with the sides nearly parallel and 
the lower extremity scarcely at all pointed. In D. tuberculosa it is very short, thick, and 
well and regularly formed, as indeed it usually is in these animals. The internal per* 
cardial laminz are always present; and in D. nigra (Pl. XVII. fig. 45) they do not die 
gradually out, as they do in D, gemmacea, but terminate abruptly behind. 
Nervous System.—The nervous centres are composed of the cerebral and buccal, 0% 
as they have been termed in Doris, the supra- and infra-cesophageal ganglia. The A 
leds geuunecea are highly concentrated, forming a continuous nervous mass encire ju 
the proboscis. It (PL XX. fig. 5) is lobulated, however, so that the component gang 
