522 SIR CHARLES ELIOT ON THE NUDIBRANCHIATA 
high, outside. They are not at all caducous, or even easy to detach. They are not set 
in groups, though the undulation of the dorsal margin produces a superficial appearance 
of such an arrangement, but are all crowded close together, except a few large ones 
which stand further inside, 2-38 mm. from the rest. The bare space in the middle of 
the back measures 15-20 mm., and the row of cerata which forms the border, though 
very irregular, is generally four or five deep, and consists.of two large and two or three 
small ones. The shape of the cerata varies greatly. Some are symmetrically tapering, 
some cylindrical with blunt tips, and some, particularly the larger ones, are swollen at 
the bases, and taper somewhat suddenly in the upper half. The outline is irregular, 
and often presents knots and projections. The hepatic diverticula within the cerata 
are, like the cerata themselves, of irregular outline, and covered with knots, but are not 
ramified. They are similar in substance to the liver in the body, and in colour vary 
from brown to dull pink. In many cerata, at any rate, the liver cavity communicates 
with a small cavity above, which, in its turn, communicates with the exterior by a pore, 
which is sometimes visible externally. This cavity contains nematocysts of two 
shapes, spherical and elliptical. Mr G. H. Grosvenor, who has made a special study 
of these organs and kindly examined for me some from Notaeolidia gigas, informs me 
that the spherical nematocysts contain a convoluted cord inside and are of a type 
found in actiniae. In the elliptical nematocysts the cord is hard to see, but, as far as 
it can be followed, is straight. ; 
The large pericardial prominence lies a little to the right of the centre of the back, 
and is 18 mm. long by 14 broad. The genital orifices are about 38 and the anal 
papilla 52 mm. from the anterior end. This papilla lies just under the cerata, and its 
margin bears five crenulations, which are perhaps not natural. 
On opening the body, the large heart is seen. It appears to be as usual. On the 
auricle are two lumps, possibly glandular. Considering the size of the animal, the 
central nervous system is small, the eyes in particular being minute specks. The 
ganglia are yellowish-white, and arranged as usual in the Aeolididae. The cerebro- 
pleural ganglia are elliptical, the pedal rather rounder. On the buccal commissure are 
situated the two elliptical buccal ganglia, separated from one another by a considerable 
interval, and connected with the gastro-cesophageal ganglia. The other commissures 
appear to be united in a common sheath. 
The buccal mass measures 11 mm. by 14. The front part of it is formed by 
two moderately elongate jaws, which do not enclose the sides. They are brownish- 
yellow, and not very strong. The length is 8 mm., the breadth 6 mm. at the top, 
3 at the bottom. The masticatory process is 3°2 mm. long; the edge is not denticu- 
late, though it bears a few lumps and irregularities here and there. 
The radula consists of eighteen rows of yellow teeth, and this number was constant 
in the five specimens dissected. Hach row consists of a central tooth and normally 
four laterals. In some rows the outermost lateral is lost, and in one or two there appears 
to be a fifth rudimentary plate. The radula is brittle, and the central tooth liable to 
