1 903 Colour in Fishes 2 1 5 



shore or in a boat), afford greater protection than if the 

 fishes were dull brown or black. 



I have, so far, written only of sea-fish, for the simple 

 reason that my acquaintance with them is considerably 

 more intimate than with those of fresh water, but there is 

 little difficulty in showing, even with an only superficial know- 

 ledge of the latter, that the same rule applies. The spotted 

 trout is safe against a background of gravel in running 

 water, as the duller bream and carp are eminently suited 

 to an environment of mud and reeds. Any comparison, 

 however, of the degrees in which colour protection works 

 out in salt water and fresh, must necessarily be based on a 

 proper appreciation of, and allowance for, the very different 

 depths that obtain. Although practically the entire sea- 

 bed which comes within the operations of the longshore 

 fisherman lies in the sun's influence, there are greater 

 depths of equal, perhaps of greater, interest to the 

 naturalist, which are far beneath the light of day. In such 

 situations the problem of colour protection obviously be- 

 comes reduced to its minimum importance, though other 

 factors, which need not here detain us, may there come 

 into operation. As regards our river fish, their life is 

 clearly passed in the light zone, and, indeed, colour pro- 

 tection is in one sense of yet greater importance to them 

 than to their brethren of the salt, though in another, seeing 

 that their natural enemies are somewhat fewer, it may be 

 less so. 



The question of colour as seen in the water has an- 

 other and distinct interest for the fly-fisherman, who has to 

 discuss the sensibility of salmon or trout to the colours of 

 flies thrown from above and therefore seen by them against 

 a background of sky ; but this is perhaps a little wide 

 of the present subject. All that I have endeavoured to 

 accomplish, in a short space, is to show some measure of 

 scheme in the coloration of a most interesting group of 

 animals peculiarly adapted to existence under water. 



