Colouration of Trout. 225 



• know, is piscis integer et innocens as regards those disgusting 

 parasites.* 



The effects of LIGHT on the colouring of fishes are well- 

 known, and doubtless the denizens of the Canadian rivers must 

 be materially influenced in these respects, seeing that the fresh 

 waters are hermetically sealed for nearly half the year, whereby, 

 moreover, we are debarred from knowing what may be going 

 on in relation to their migratory movements. Indeed, I have fre- 

 quently noticed in brooks and rivers free from obstructions, that 

 the trout is far more highly and brightly coloured, and in better 

 condition, than the same species inhabiting waters shut off from 

 the sea by impassable waterfalls or artificial obstructions. This 

 is so very apparent that every one experienced in Canadian 

 trout fishing can at once make out the difference. Thus 

 the more rapid the stream and the less shaded by forest, 

 with a pebbly bottom, the more brilliantly and clearly 

 coloured are its fishes ; moreover, this is so conspicuous 

 as regards the brook trout, that the red-bellied variety 

 was at one time considered to be a very good species.f 

 In fact, the more one sees of fishes in nature, the more 

 it becomes apparent that by trusting to colouring and 

 other external characters, influenced by locality and seasonal 

 changes, there is a certainty of falling into the grave error of 

 proclaiming objects as distinct species which are only varieties. 

 I am sadly afraid many naturalists in their zeal do delight in 

 " species manufacturing," and care little for what the future 

 may disclose, when the "truth will out," and all their beautiful 

 species must cease to be considered other than forms of what 

 had been described previously. In no branch of Natural His- 

 tory is this more apparent than among- fishes, and especially the 



* Dr. Holmes, in the Maine Report before quoted, speaks of a species 

 of caligus which infests the scales of this trout. I looked for it particu- 

 larly, but failed in discovering the parasite. Perhaps it is peculiar to the 

 lake life of the fish, and disappears when the latter enters the rapid streams 

 in June, which to the above is seemingly as the sea is to the salmon. 



t " Natural History of New York," vol. hi., p. 236, pi. 39, fig. 136. 



Q 



