152 nereidjE. 



and well developed ; and there is a pair of large clavate organs at its 

 junction with the first segment, by the aid of which the little crea- 

 ture appears to move through the water, for in this stage of its life 

 it is an excellent swimmer as well as a swift creeper. There is a 

 prominence at the base of each, perhaps the buds of future tentacular 

 cirri ; and here we observe underneath some minute ciliated orgau, 

 by whose play a current of water is driven violently along the sides. 

 By the play of other ciliated organs at the tail, similar currents are 

 there created and kept up ; and the whole process forcibly recalls to 

 memory the mechanism by which respiration is carried on in many 

 of the edriophthalmous Crustacea. The eyes are in a straight line, 

 and not less distinct than in the adult. The feet are well developed, 

 biramous ; the caudal segment rounded, of a dark colour, and ciliated 

 all round. I found these supposed young in the beginning of Sep- 

 tember amongst Confervse ; they were about two lines in length, and 

 very active. 



The luminous animalcule sometimes to be seen on the shells of 

 oysters, and dehneated by Baker (Employm. for the Micros, p. 399, 

 pi. 15 A), seems to be the same worm, a little further advanced. 

 The tentacula are now developed, as well as a single pair of the ten- 

 tacular cirri. " This little insect," says Baker, " can emit or conceal 

 its light ; and sometimes its lustre is so bright as to be discoverable 

 even in open daylight, especially on being touched or disturbed. 

 Its light is bluish like that of the glow-worm, or a spark of burning 

 brimstone." 



Quatrefages has been led, from the microscopic study of the small 

 transparent Annelides, " to infer that its production depends very 

 intimately upon the influence exerted by the nervous system in giving 

 rise to muscular contraction." — Ann. ^ Mag. Nat. Hist. xiv. 34. 

 See Ray Soc. Rep. Zool. 1847, 504. 



3. N. diversicolor, post-occipital segment twice as long as the 

 second, the tentacular cirri once and a half as long as its breadth ; 

 feet with subequal conoid parallel lobes, the dorsal somewhat 

 humped, most so on the posterior feet ; upper setigerous branch 

 obsolete ; terminal piece of the bristles smooth ; dorsal cirrus 

 scarcely reaching beyond the apex of its lobe ; jaws with ten den- 

 ticulations. Length 4-8". 



Die bunte Nereide, Mull. Wurm. 104. tab. 6. 



Nereis diversicolor, Milll. Zool. Dan. Prod. 21/. no. 2624. Fabric. 



Faun. Groenl. 291. Oersted, Annul. Dan. Consp. 23. pi. 4. f. 66, 



68 & 73; Granl. Annul. Dorsihr. 24 j and in Kroyer's Naturh. 



Tids. 118. 

 Nereis versicolor, Ttirt. Gmel. iv. S6. 

 Lycoris margaritacea !, Leach in Mus. Johnston in Zool. Journ. iv. 



420 ; and in Loud. Mag. Nat. Hist. vii. 230. 

 Lycoris viridis, Johnston in Zool. Journ. iv. 419, 

 Nereis pelagica, Johnston in Ann. Nat. Hist. iii. 290. pi. 6. f. 1. 

 Nereis viridis, Johnston iv Ann. Nat. Hist. v. 171. 



