50 THE SPORTING FISH 



geological strata of the beds, and nature and quan- 

 tity of food supplied by the brooks, streams, rivers, 

 ponds, lynns, and lakes in which it is bred. The 

 diversity of colouring is, in fact, a defence fur- 

 nished by nature for the preservation of the fish, 

 which would otherwise be so plainly visible upon 

 the slightest change of water or soil as to fall an 

 easy prey to its enemies, whether biped or quad- 

 ruped ; and experiments have shown that the 

 change is a question of minutes rather than of days 

 or weeks. Upon its transfer from a light- to a 

 dark-coloured vessel, or vice versa, the hue under- 

 goes an instant alteration, and in a very short time 

 assimilates itself more or less perfectly to that of 

 its new domicile. Thus, for instance, the Trout of 

 Lynn Ogwin, almost the whole bottom of which is 

 formed of s^rass, have, when first caught, a brilliant 

 emerald gloss over their golden and yellow tints ; 

 and although the waters are of the utmost clear- 

 ness and the lake swarming with fish, I was never 

 able in any one instance to distinguish these from 

 their surrounding green. Again, in the Spean 

 Water, Inverness, there are several small tarns in 

 which I have frequently taken fish of almost the 

 colour of ink ; yet these tarns actually join the 

 Spean, where many of the Trout are of a fine rich 

 yellow, — the cause of the difference being that the 

 river has a bed of gravel, whilst the tarns are 

 floored with a deep deposit of bog mud. I have 

 even known a similar difference to exist between 



