76 SALMONIA. 



muscles of the legs and thighs are the best 

 parts for the epicure, a large quantity of flesh 

 being developed there, but not yet hardened 

 or rendered tough by exercise. These facts 

 are of the same kind, and depend on the same 

 principles, as the peculiarity of the breeds or 

 races in trouts. Fish in a clear cool river, that 

 feed much on larvae, and that swallow their 

 hard cases, become yellower, and the red spots 

 increase so as to outnumber the black ones ; 

 and these qualities become fixed in the young 

 fishes, and establish a particular variety. If 

 trout from a lake, or another river of a different 

 variety, were introduced into this river, they 

 would not at once change their characters; but 

 the change would take place gradually. Thus 

 I have known trout from a lake in Scotland, 

 remarkable for their deep red flesh, introduced 

 into another lake, where the trout had only 

 white flesh, and they retained the peculiar red- 

 ness of their flesh for many years. At first they 

 all associated together in spawning in the brook 

 which fed the lake, but those newly introduced 

 were easily known from their darker backs 

 and brighter sides. By degrees, however, 



