16 VARIETIES OF TROUT. 



ciently correct ; although it is by no means made 

 clear that even those varieties may not have been 

 derived from the common trout, altered by cir- 

 cumstances and characterised by peculiarities 

 transmitted through a succession of generations, 

 but not the less varieties on that account.* As 

 to species, there can be no doubt that whatever 

 may be the case with naturalists, the unlearned 

 are certainly apt to multiply them, either from an 

 imperfect comprehension of the term, or from 

 being deceived by the external appearance and 

 colours of the fish, from which a hasty opinion 

 ought not to be formed,. " The colouring mat- 

 ter," says Sir Humphrey Davy, " is not in the 

 scales, but in the surface of the skin immediately 

 beneath them, and is probably a secretion easily 

 aifected by the health of the animal." The 

 soil, the season, and the water undoubtedly exer- 

 cise considerable influence on the colours of fish, 

 and that the food does so has been satisfactorily 

 proved by an experiment made some years since 

 in the south of England, and thus recorded by 

 Mr. Stoddart : " Trout were placed in three 

 separate tanks, one of which was supplied daily 

 with worms, another with live minnows, and the 



* See Salmonia, pp. 65 72. ; also, Combe's Constitution 



of Man ; and the Vestiges of Creation. 



