On Hippolyte fascigera and H. gracilis. 147 



XIX. — Hippolyte fascigera, Gosse, and H. gracilis (Heller). 

 By Alfred 0. Walker. 



In September last I received from Mr. F. W. Gamble, who 

 is working at the physiological causes of the variability in 

 colour of Hippolyte varians, Leach, a specimen which he 

 rightly considered to be H. fascigera, Gosse. The colour of 

 the specimen, when received by me in formaline, was pale 

 green, and, with the exception of the tufts of plumose setse on 

 the body, does not differ from H. varians. 



H. fascigera was described by P. H. Gosse in the Ann. & 

 Mag. Nat. Hist. ser. 2, vol. xii. (1853) p. 153. He says the 

 tufts are " very deciduous," and, " when wanting, the animal 

 may easily be mistaken for H. varians" &c. Further, he 

 says that " it may be distinguished at once, while alive, by 

 its colour, which, though varying, does not assume any of the 

 phases of H. varians. It is usually pellucid white, clouded 

 with opake drab, and generally blotched with dark reddish 

 purple." Again, he states that the relative position of the 

 teeth on the lower margin of the rostrum and " the relation 

 of the filaments of the internal antennas to each other in 

 length and thickness also afford a good distinction." 



In 1882 Prof. G. O. Sara (' Oversigt af Norges Crustaceer,' 

 p. 46 [separate copy]) says that he is still doubtful of the 

 specific distinctness of H. ( Virbius) fascigera from H. varians, 

 but he agrees with Gosse's description of its colour. 



Prof. W. A. Herdman, F.R.S., in an article on the pro- 

 tective colouring of //. varians, in Trans. Liverpool Biol. 

 Soc. vol. vii. (1893) p. 77, says that "specimens found on a 

 sandy bottom or on small gravel are mottled black, grey, and 

 white." 



My own experience agrees with the last writer's, but I am 

 not prepared to say that these forms had not the tufts of 

 plumose setas, as when I took them my attention had not been 

 directed to H. fascigera. In looking through a number of 

 H. varians in spirit from rock-pools on this coast, I had no 

 difficulty in finding four or five tufted specimens, but their 

 colour had gone. In other respects there is no difference 

 between them and the ordinary form. 



It is well known that H. varians is not only variable in 

 colour, but almost, if not quite, as variable in the dentition of 

 the lower edge of the rostrum. Kinahan (Nat. Hist. Review, 

 vol. iv. (1857) p. 518) says "a volume might be written on 

 the forms of the beak of this species " ; he figures six varieties 



