The Natural History of the Salmon. 65 



crustaceans, sand eels, etc., with their former weight 

 in ounces increased to pounds. 1 



" It is apparent from the foregoing remarks that 

 the distinction of the various species of Salmonidae 

 is a matter of considerable difficulty, and that there 

 is scope for great diversity of opinion ; at any rate, 

 it is only by a close, long-continued study, and con- 

 stant comparison of specimens of various ages and 

 from various localities, that one is enabled to find a 

 guide through the labyrinth of confusing variations. 

 However, it is a significant fact that the very same 

 characters by which we are enabled to distinguish 

 European species occur again, though in an ex- 

 aggerated form, in American Salmonoids (which 

 everybody will admit to be of distinct species), and 

 therefore our faith in them necessarily becomes 

 strengthened. In accordance with acknowledged 

 principles in zoology, forms which differ from their 

 congeners by a combination of two or more constant 

 characters, are to be distinguished under distinct 

 specific names. Most likely they have been derived, 

 at a not very remote period, from common ancestors, 

 but the question of their specific distinctness is no 

 more affected by this consideration, than the ques- 

 tion whether Salmo and Coregonus are distinct 



1 This entirely depends on the amount of food, and locality ; 

 I have killed grilse (*'.., salmon of the first return from the 

 sea) of twelve pounds and of two pounds respectively. (H.) 



F 



