20 "BRITISH SPORTING FISHES. 
spotted trout is, and also that it greatly varies in 
colour. Trout have the power to take on 
themselves the colour of the stream which they 
haunt, and no fresh-water fish conforms more 
admirably to its environment. This is one of the 
most remarkable traits in the fish’s economy. 
Other local conditions greatly affect the species. 
Those in lakes attain to a considerable size, and 
their predatory instincts are greatly developed. 
The fact of trout interbreeding with salmon has 
been already mentioned, as has also the fact of the 
fertility of the produce. Trout are subject to the 
same devastating disease as salmon, and of late 
years several of the best trout-streams in the 
country have been almost depopulated by its 
agency. 
