LEPTONEREIS. 263 



maxillae, but gave it no distinctive name. It probably is an older example of the same 

 species. 



De Quatrefages (1865) thought that in regard to the fusion of the head and buccal 

 segment and in the structure of the feet it diverged from the Nereids ; indeed, he would 

 have considered it a larval form if Claparede had not found ripe ova. Ehlers, on the 

 other hand, is doubtful concerning its position, and would even connect it with the 

 Aphroditidae. 



De St. Joseph 1 places Micronereis under the group devoid of paragnathi and having 

 a biramous foot, by which it is distinguished from Lycastis ; whilst it is separated from 

 Leptonereis, which he places next it, by having bristled feet on its buccal segment. 

 Gravier 3 follows a similar arrangement. 



Racovitza (1893) gave an interesting account of the sexual distinctions of this form, 

 only the females of which, with twenty-one pairs of feet, had been seen by Claparede and 

 De St. Joseph. He found the male very minute, only 2 mm. long, or half the length of 

 the female, and with fewer feet — sixteen to seventeen pairs. Moreover, it has copula- 

 tory ventral hooks on the third pair of feet which do not exist in the other sex. The 

 maxillae likewise differ, for they have in addition to the smaller teeth three larger 

 posterior points. On the other hand the female has only five teeth. The reddish eggs, 

 which are about sixty in number, are deposited in glairy mucus, and the larvae escape 

 from this when they have five pairs of feet. The mature female undergoes considerable 

 changes. Thus tlie cirri enlarge, become ovato-lanceolate, and the anal cirri are elongated. 

 The posterior region of the body seems to be paralysed, and the animal drags it through 

 the glairy mucus by aid of the anterior region. This author a little later 3 gave a 

 description of the amoebocytes, the ovogenesis, and the deposition of the eggs in the same 

 form. 



When observed in life in Guernsey it was at first sight, from its activity, associated 

 with the Hesionidae, but a more careful examination, independently of any reference to 

 literature, shoAvecl that it most nearly approached the Nereids, a conclusion which 

 substantiates the original view of Claparede and of others subsequently. 



Genus LIX. — Lkptonereis, Kinberg, 1865. 



Head rounded in front, eyes large, buccal segment and tentacular cirri shifted 

 forward ; anterior dorsal cirri peculiarly modified ; tail with two bluntly conical lamellae 

 and two slender subulate cirri above them. 



Foot without spine or bristles dorsally in the first two segments, the rest boldly split 

 into two divisions. 



Leptonereis was constituted by Kinberg 4 one of the genera of his family Niconidea in 

 which the paragnathi are absent. He characterizes the new genus as devoid of paragnathi 



1 ' Ann. Sci. Nat./ 8 e ser., t. v, p. 285, 1898. 



2 ' Nouv. Arch. Mus./ 4 e ser., fc. in, p. 155, 1901. 



3 'Compt. Rend. Acad. Sci./ January, 1894. 



4 ' Ofvers. k. Vet.-Akad. Forh./ 1865, p. 179. 



