COLORATION AND MIMICRY 



293 



experiment] the blackest ground produced no change of 

 colour unless the amount of light was diminished." 



This has not been my experience ; for in the pond above 

 referred to the amount of light was constant a fair sub- 

 dued light, coming through the water of the large tanks 

 which formed the walls of the room, 



Mr Beddard also lays stress upon the " extremely con- 



Fig. 122. The Plaice. Platessa vulgaris. Natural size 



spicuous " white line on the fins of the sole, that did not 

 disappear under any of the conditions, but Mr Beddard 

 does not point out that, in nature, the sole, and all other 

 flat fish, on alighting on the bottom always flaps up some 

 of the sand gravel or mud, so as to cover the fins and obscure 

 the fish's entire outline (see Figs. 122 and 123). 



