28 OLD FLIES IN NEW DRESSES 



suppose that the trout is normally colour- 

 blind. 



As Michael Foster so ably put it, " No 

 man can tell what are the sensations of his 

 fellow-man," still less I think can man say 

 what are the sensations of a trout. All 

 we can do with regard to this question of 

 colour vision, is to find out all the facts we 

 can relating to it, and working on com- 

 parisons, arrive, not at conclusions, but 

 at probabilities. 



The only thing of which I am sure is 

 that we shall find it safe and comparatively 

 easy to imitate flies in colours, but to make 

 a monochromatic imitation of one, which 

 would accurately represent it to a normally 

 monochromatic eye (about which we know 

 nothing), in a medium of which we know 

 very little, is practically impossible. 



