COLORATION AND MIMICRY 285 



feed on all that comes to the cilia, and none (or few) of 

 these microscopic things are pigmented. 



In regard to all these forms, and possibly many others, 

 we are without a glimpse of light, and the subject offers a 

 fine field to the young and serious naturalist. 



Arrived at the Crustacea, we do begin to find a raison 

 d'etre for special colours. Allusion has been made in 

 Chapter VII. to the bright colours and rapid changes from 

 one to another in the Hippolytes H. varians, above all, 

 changing from a bright red to a vivid green in a very short 

 time. 1 All the Hippolytes have this faculty, in various 

 degrees, except one, a large and beautiful species, which, I 

 think, is the Hippolyte Thompsonii of Bell, but am not 

 sure. This one is of large size, about an inch and a half 

 ong, and fairly stout. 



The general tint of this is nil that is, it is just about 

 transparent but on two of the joints of the abdomen are 

 large opaque saddles of a rich pink, as if patches of satin 

 of this colour had been pasted on. It lives amongst pink 

 corallines, or rather nullipores, at the low-tide limit (and 

 no doubt extends to deep water), at least the specimen 

 before me was taken in such a locality, and it was trans- 

 ferred to a glass tank with bits of nullipore, where it was 

 practically invisible. 



It has some minute purple and lemon-coloured dots 

 arranged alternately in lines on the limbs and around the 

 carapace, but these only show on close examination. 



This, of course, looks like a good case of mimicry, but 

 then it occurs why the pink saddles ? Would not com- 

 plete transparency be as good ? Well, no. The largest 

 patch occupies that segment on the abdomen which forms 

 a conspicuous hump, and a fish passing by would be 



1 I have sometimes had Hippolyte change from red to green in 

 a plain white dish, with apparently no stimulating cause ? and 

 this at night, 



