PCECILOCHJETUS SERPENS. 233 



examples of a pelagic larva off the coast of Normandy, a larva he had previously met 

 with on the coast of Norway in 1855. Though he did not assign a name to it, his expe- 

 rience enabled him to recognise certain fragments procured in the ' Lightning ' Expedition 

 as pertaining to the adult form of the larva formerly mentioned. Ehlers, 1 who included 

 Claparede's account at the commencement of his paper on the annelids of the ' Porcupine 5 

 below 500 fathoms, also makes remarks with figures, on two specimens of the same form. 

 Claparede thought that it could not be included in any known family, and he called it 

 Poecilochmtus fiilgoris. 



Levinsen 2 (1883), who had examined the larval stages from the Skager Rak, showed 

 that Pceciloclisetus was closely allied to Disorna, (Ersted, and he ranged both under the 

 Spionidas. 



The larval form was found generally in the tow-nets in St. Andrews Bay from July 

 to October, 3 showing that the adults could not be far removed, yet up to date not a single 

 adult has been captured. Nothing can better illustrate the safety of many forms, even so 

 high as fishes, in the sea. 



1. Pcboiloohjitus sbrpens, Allen, 1904". Plate XCII, fig. 4 ; Plate XCIV, figs. 15 and 1 5 a ; 

 Plate CI, figs. 3 and 3 a— head and tail; Plate CVII, fig. 17— bristle; Plate CXI, 

 figs. 11 — 11 e — bristles and hook. 



Specific characters.— Nuchal organ greatly developed in the form of three long 

 tentacle-like processes. Anterior dorsal surface with few tubercles. Cirri of segments 

 seven to thirteen different from the others, being flask-shaped, with long, stiff necks. 

 Second and third segments have short, stout spines ventrally. Anterior region coloured 

 red from the blood. 



Synonyms. 



1863. Unbekanuten Riikenkiemer gehorigen Larve, Claparede. Beobacht., p. 77, Taf. vi, figs. 1 11. 



1904. Poecilochsetus serpens, Allen. Quart. Journ. Micr. Sc, vol. xlviii, n.s., p. 79, pis. 7 12. 



» » „ . Journ. M. B. A., vol. vii, p. 228. 



Habitat. — In sand at Plymouth. 



A considerable step in advance was made by the discovery of the adult form in tubes 

 in sand at Plymouth, so that Dr. Allen was enabled to give a careful account of it with 

 figures. 4 



The head (Plate XCII, fig. 4, and Plate CI, fig. 3) is small and hemispherical, bearing 

 two small dorsal, and two larger ventral eyes, whilst beneath it is a short median minutely 

 papdlose tentacle, the base of which is within the mouth when the proboscis is withdrawn. 

 The great lateral tentacles or palps arise immediately behind the head and extend to at 



Zeitschr. f. wiss. Zool./ Bd. xxv, pp. 2—13, (p. 62), 1875. 

 ( Nat. For. Yid. Meddel./ 1883, p. 103. 

 Quart. Journ. Micr. Sc./ vol. xxxvi, N.s., p. 71, pi. viii, figs. 4—7. 

 4 Ibid., vol. xlviii, n.s., pp. 79—151, pis. vii— xii, 1904. Much of this account is taken from Dr. 

 Allen's description. 



153 



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3 ( 



