THE FLAT-FISHES 213 



variable. Holt* has described a race of dwarf Baltic plaice 

 with spinous, or ciliated, scales — a character unknown in the 

 plaice of our grounds ; and Cunningham f once made a detailed 

 comparison of the different races of plaice from representative 

 grounds between Plymouth and the Dogger Bank, in which he 

 was able to show a great margin in respect of many distinctive 

 characters. 



Colour variation is also a common phenomenon in the 

 flat-fishes. As has already been described, the colouring is 

 usually confined to the upper (in reality, right or left) surface. 

 In nature, however, all manner of changes are rung on this 

 condition, and examples are recorded with the colouring only 

 on the wrong side, or with equal colouring on both. Bateson { 

 describes small brill and plaice sent to him from Mevagissey 

 by the late Matthias Dunn, as well as flounders captured in 

 the shallow water of Bournemouth Bay, all of which had 

 colouring on the normally white, or "blind," side. With refer- 

 ence to the Bournemouth flounders, the writer has, during a 

 residence of seven consecutive winters at that town, repeatedly 

 remarked these curiously coloured flounders in the shops, and 

 has been given to understand that they were caught by Poole 

 boats in the bay. In many examples the spots on the usually 

 " blind " side coalesce in such manner as to present a con- 

 siderable surface of brown colour. The most interesting 

 record, however, with regard to the colouration of one side 

 only in flat-fishes, and particularly with reference to the theory 

 of the influence of light, is that of Mr. Cunningham's ex- 

 periments § in the artificial colouring of flounders confined in 

 a tank with mirrors so arranged beneath as to throw up the 

 light on the lower side of the fish. In this way he actually 

 succeeded in colouring the lower side of a flounder, which 



* S&Qjourn. Mar. Biolog. Assoc, October, 1894, p. 194. 



t Qeelbid., March, 1897, pp. 315-359- 



+ See Proc. Zool. Soc, 1894, p. 246. 



§ fount. Mar. Biolog. Assoc, May, 1893. 



