246 Mr. J. Blackwall on the Salmon and Bull-trout, 



observation. Trout, suddenly transferred from their natural 

 haunts into wooden, metallic or earthenware vessels supplied 

 with water recently taken from the same stream in which they 

 were captured, speedily assume a lighter hue ; and as this change 

 does not appear wholly to depend upon the colour or capacity 

 of the vessels in which they are placed, I am inclined to attribute 

 it primarily to the influence of fear, and in this opinion I am the 

 more confirmed from having frequently perceived a similar 

 transition in the hue of salmon soon after they have been hooked 

 by the angler. That this is not the sole occasion of sudden 

 alterations in the colour of fish I readily admit, for I have often 

 disturbed small flounders in the Conway, which on changing 

 their situation and reposing upon objects of a different hue from 

 those they had last quitted, soon became accommodated to this 

 circumstance of their novel position by undergoing a modification 

 of shade which harmonized with that of their resting-place and 

 effectually served to conceal them from ordinary observation. 

 Even death, as the disciples of Isaac Walton are well-aware, and 

 as the following anecdote clearly proves, does not immediately 

 put a stop to this chameleon-like transition of tint. 



A gentleman of my acquaintance, a proficient in the art of fly- 

 fishing, had taken a young salmon weighing about a pound and 

 a half, which, in consequence of having been a long time in the 

 fresh water, had lost its brilliancy and had acquired a very dark 

 aspect ; this fish one of my children requested to be permitted to 

 carry, so after having inserted the longer and smaller end of a 

 slender forked twig under one of the gill-covers and drawn it 

 through the mouth till the prize was retained in the angle formed 

 by the fork, I gave it to the boy, who held it suspended with the 

 tail downwards. After the lapse- of several minutes, perceiving 

 that the fish had lost all its blackness and had become perfectly 

 bright, I directed the attention of my acquaintance to it, who 

 could scarcely be persuaded that it was the same which he had 

 captured a short time before, but supposed that I had secretly 

 substituted another for it ; however, the speedy resumption of its 

 former dark complexion, which underwent no further mutation, 

 completely convinced him of its identity. 



I shall not attempt to offer any explanation of the remarkable 

 physiological phenomenon here recorded; but, apart from the 

 mysterious operation of psychological agency, its cause must un- 

 doubtedly be sought for in the organization of the rete mucosum. 



