210 ANGLING. 



short time was exceedingly striking. With the 

 view of ascertaining what effect the light had in 

 producing this extraordinary change, I next al- 

 lowed the fish to remain in the white basin so long 

 as effectually to acquire the light tint, when I ex- 

 cluded the light from them altogether by covering 

 the basin with a thick mat, and on removing it a 

 few minutes afterwards, I found the fish were 

 again changed to a dark colour, which gradually 

 disappeared on exposure to the light. The change 

 of colour is produced alike under a bright or cloudy 

 sky. This singular phenomenon, with which I 

 have only now become acquainted, adds another to 

 the many beautiful provisions Nature has made for 

 the safety and protection of her creatures. The 

 cause, however, is a problem I make no pretensions 

 to solve."* 



We think that this principle of change accounts 

 in some measure for the different aspect of fishes 

 in different rivers, as well as in various parts of 

 the same river. The Tweed, the Tay, the Dee, 

 the Don, the Annan, although composed of many 

 varied features, have each a character of their own, 

 which becomes impressed on the external aspect of 

 their finny inhabitants. Experienced fishermen 

 tell you that they can distinguish the salmon of 

 one river from those of another, that is, that they 

 have taken cognisance of the general aspect and 

 physiognomy which distinguish the natives of each, 

 and can thus point out such as have wandered from 



* Edinburgh New Philosophical Journal for January 1838. 



