148 Mr. A. 0. Walker on 



on pi. x. (ix. in error). It is, however, to be noted that all 

 these and all the specimens I have ever seen of H. varians, 

 as well as Gosse's species, have only one tooth at the base of 

 the rostrum, on the upper margin, and that the lower margin 

 in adults is more or less strongly convex. 



Gosse's distinctive characters therefore, besides the fascicles 

 or tufts, consist practically only of the colour, the position of 

 -the teeth on the lower margin of the rostrum (both of which 

 are notoriously variable), and the relative thickness of the 

 antennular filaments, which is purely a matter of age and sex. 



Mr. Gamble informs me that a fascigerous specimen shed 

 the fascicles during life, so that they do not appear to be an 

 integral part of the integument. And if it can be shown that 

 similar tufts of setae occur on at least one other species of 

 Hippolyte, as I propose to do, their specific value disappears. 



In the 'Journal of Marine Zoology,' vol. ii. p. 101, the 

 editor, Mr. Jas. Hornell, has an interesting article on " The 

 Protective Colouring of the iEsop Prawns," in which he 

 mentions that H. varians, when moved to water containing 

 weeds of a different colour from its original habitat, changes 

 its colour to that of the weeds in a single night. He goes on 

 to say that H. fascigera has much less power of colour 

 adaptability, that it " is seldom found in any number except 

 among tufts of coarse CoraUina, with which it agrees abso- 

 lutely in colour," and that its " tufts of brush-like hairs " 

 harmonize with the minute tubicolous Annelids and Bryozoa 

 of the rock-pools it inhabits, so that " the mimetic adaptation 

 is greatly accentuated." But he adds in a footnote that it 

 differs from II. varians in that " the only spines on the upper 

 edge of the rostrum are three placed at the posterior end and 

 really upon the carapace, while a single sharp tooth is set 

 close to the tip on the straight under edge." Had Mr. Hornell 

 seen Gosse's description of H. fascigera he would have recog- 

 nized that the rostrum there described differed entirely from 

 his. At my request Mr. Hornell kindly sent me a specimen 

 which is certainly well furnished with the tufts of setae, and 

 as certainly is not H. fascigera, Gosse ; it is, in fact, H. gracilis 

 (Heller), a species not hitherto, so far as I know, recorded 

 west of the Mediterranean. 



According to Czerniavsky ( l Crustacea Decapoda Pontica 

 littoralia,' 1884, p. 15, pi. i.) the rostrum of this species is 

 very variable. He figures ten or eleven forms in which the 

 number of teeth on the upper edge at the base of the rostrum 

 ranges from two to five, and those on the almost or quite 

 straight (sometimes slightly concave) lower edge from one to 



