292 NATURAL HISTORY OP OUR SHORES 



stituents, are spotted, black and yellowish white, in exact 

 resemblance to this sand (Fig. 53). 



Many fishes control their pigments to suit surroundings. 

 The best " mimics " in this way are the brill and the turbot ; 

 in less degree the plaice, sole, etc. 



An illustration easy to hand is the little minnow of our 

 streams. 



If two suitable vessels, say dessert plates, one red and one 

 green, are used, and the fishes, whatever may be their tint, 

 are placed in one of these, they will in a few minutes take 

 on, not the exact colour, yet one so similar that they are 

 scarcely visible ; then if transferred to the other they will 

 be strikingly obvious, but only for a minute or two they 

 will quickly put on the new colour. 



For a year I kept a Turbot, which was about a foot long, 

 in a shallow pond (in the Jersey aquarium). The pond 

 was about twenty feet long by eight feet wide. The 

 bottom was arranged in three sections : one ordinary grey 

 sand, the next shell gravel, with large bits of oyster shell- 

 etc., and the rest shingle, with black, buff, and white pebbles. 



As the turbot rested upon either of these it was as 

 difficult to perceive it as the South Kensington duck. 



I have seen visitors look for it for a quarter of an hour, 

 while it was fully exposed in front of them. 



If it was driven to another kind of bottom say on the 

 shingle it appeared strongly evident as a whitish patch ; 

 but only for a few minutes : gradually black, buff, and white 

 spots and dashes would appear, until again it was lost to 

 view. 



The change from light and even colouring to a strongly 

 marked one took about five minutes, while the reverse 

 process was much more rapid. 



Mr Beddard (" Animal Coloration "), referring to the Sole, 

 says : " The changes of colour depend not on the nature of 

 the ground, but on the amount of light, for [referring to an 



