384 0)1 two rare British Nudihranchs. 



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 a single series of 15-16 teeth, the first two or three of 

 which are simple, the rest set with extremely fine tubercles, 

 lladula 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 difTuse, with anterior and posterior branches, the latter 

 supplying the dorsal jiapilljB. The nervous system similar to 

 that of iEolidiidaj. Eyes well developed. Otocysts with a 

 single otolith. Penis unarmed. The spermatozoa similar to 

 those of jEolidiidffi. llancockia appears to be mature when 

 about half an inch in length. Trinchese 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 llancockia to see if the dorsal papillae would 

 respond, as they do in Lomanotus ; no effect, however, fol- 

 lowed. The presence of cnidocysts in the genus described 

 by Trinchese as occurring at the tips of the pleuropodial lobes 

 (loc. cit. pp. 18G, 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, Avitli 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 Deles- 

 seria on which it lived. Unfortunately I made no experi- 

 ments to ascertain whether llancockia responds to shadows as 

 stimuli. The large eyes noted by Trinchese would be in 

 favour of such reaction. llermaa h(fida, which lives on 

 Delesseria, and certain Eolids have been shown by Mr. Gar- 

 stang to respond f- 



As regards the systematic position of llancockia. Gosse 

 placed it in the Tritoniidaj ; Trinchese, Bergh, Xorman J, 

 and Cams place it in the Dotonidte ; Bergh, however, adding: 

 " Bei dcr Formulirung der Charaktere der Dotoniden ist auf 



* "Pio Cladoliopatit^chen Nudibraucbieii," Zool. Jahrb. v. p. 63. 



t Ciarstaii<r, " Complete List of Plyiiiouth Opisthobraucus," Jouru. 

 Mar. Biol. Assoc, (u. y.) i. uo. 4, p. 4'23. 



X " Revision of British Mollusca," Auu. .S: Mag. N. II. vol. vi. ISW, 

 p. 79. 



