113 SALMONID^. 



of this view of the subject, I will remark here, that one of the 

 principal external differences between the American and the 

 European Trout is precisely as might be expected under the 

 A-iews taken above. The climate here being far more sunny, 

 the atmosphere drier and more transparent, and the weather 

 more constant and lightsome, we find that the Trout of America 

 is a lighter-coloured, brighter, gayer, and more gorgeous creature 

 than his European kinsman. And, farther yet, we shall find 

 that in the purest and most limpid streams, in the lakes which 

 to the most transparent waters add the sunniest expanse, the 

 brightest and most beautiful Trout are taken ; while in the black 

 bossrv waters, or in foi'est-embowered rivers, the colours of the 

 fish are likewise dim and dusky. 



This is not, however, merely a matter of theory and analogy, 

 for experiments have been actually tried on this point, and with 

 perfect success. Mr. Agassiz assures me that he has repeatedly 

 known very brilliant and gaily-coloured fish, taken in clear and 

 sunshiny waters, and transferred to neighbouring pools or 

 streams of totally different character, to begin to fade and lose 

 the intensity of their colours, sensibly, within a very few hours, 

 and after a few days or weeks, to be entirely undistinguishable 

 from the native fish of the place. 



This accounts, at once, for the facts so often stated, and 

 seemingly so inexplicable, of two lakes communicating with each 

 other by a common channel, and containing two distinct varieties 

 of Trout, one beautiful, and excellent upon the table, the other 

 dark-coloured and ill-tasted, the two varieties never being known 

 to intermingle, or to exchange from one to the other water. 



The explanation of this apparent phenomenon is, that the 



