384 On two rare British Nudibranchs. 
Our knowledge of the internal anatomy of these forms is 
limited to the preliminary paper by Prof. Trinchese before 
referred to. ‘The cutting-edge of the jaw is short and armed 
with asingle series of 15-16 teeth, the first two or three of 
which are simple, the rest set with extremely fine tubercles. 
Radula triseriate ; the teeth of the median row with lateral 
denticles; the lateral teeth broad, unarmed (“ quasi omnino 
illi Galvinarum similis,” Bergh *). Salivary glands large. 
Liver diffuse, with anterior and posterior branches, the latter 
supplying the dorsal papillz. The nervous system similar to 
that of AMolidide. yes well developed. Otocysts with a 
single otolith. Penis unarmed. The spermatozoa similar to 
those of Afolidide. LHancockia appears to be mature when 
about half an inch in length. ‘T'rinchese describes ripe gene- 
rative products at this stage, and Gosse has figured and 
described the spawn deposited by a specimen of this size. 
The ribbon was in the form of two complete figure-of-eight 
coils, the ova being irregularly scattered. My specimen was 
only a quarter of an inch long, and during the fortnight that 
I kept it no spawn was shed. 
I stimulated Hancockia to see if the dorsal papille would 
respond, as they do in Lomanotus ; no effect, however, fol- 
lowed. The presence of enidocysts in the genus described 
by Trinchese as occurring at the tips of the pleuropodial lobes 
(loc. cit. pp. 186, 189, and plate, figs. 8 and 14) makes its 
behaviour contrast still more with that of Lomanotus. 
While gliding over the bottom of the vessel in which it 
lived it would sometimes stop, raise the anterior part of the 
body, and, with the velar tentacles and the rhinophores well 
expanded, it would sway from side to side. In a short time 
the action ceased and the animal went straight to the Dedes- 
serta on which it lived. Unfortunately I made no experi- 
ments to ascertain whether //ancockia responds to shadows as 
stimuli. The large eyes noted by Trinchese would be in 
favour of such reaction. Hermea bifida, which lives on 
Delesseria, and certain Eolids have been shown by Mr. Gar- 
stang to respond J. is 
As regards the systematic position of Hancockia. Gosse 
placed it in the Tritoniide ; ‘Trinchese, Bergh, Norman f, 
and Carus place it in the Dotonide; Bergh, however, adding: 
‘¢ Bei der Formulirung der Charaktere der Dotoniden ist auf 
* “Pie Cladohepatischen Nudibranchien,” Zool. Jahrb, y. p. 53. 
+ Garstang, “Complete List of Plymouth Opisthobranchs,” Journ. 
Mar. Biol. Assoc. (n. s.) i. no. 4, p. 428. 
{ “Revision of British Mollusca,” Ann. & Mag. N. H. vol. vi. 1890, 
p. 79. 
