A THEORY 93 



theory, if it approaches the truth, should 

 include an explanation of why the salmon 

 takes the fly. 



We know but little of the world as it 

 appears to the eye of the fish, but from the 

 little that is known something may be 

 deduced which carries this theory a little 

 further. In the sea many and very vari- 

 ous effects may be produced upon objects 

 moving through the water when passing be- 

 tween the eye and the surface, by light, by 

 the reflecting powers of the bottom of the 

 water, and by the relative clearness of the 

 water, all of which factors of the effect pro- 

 duced vary to an almost incalculable extent. 



Given a bright sun, a light sandy bottom 

 and clear water, a small crustacean swim- 

 ming between the eye of the observer and 

 the surface often will not appear to be 

 like the creature when it is seen out of 

 the water. The outline will be indistinct, 

 and the whole will frequently appear to 

 be brilliantly coloured. Not only is the 

 body thus brilliantly coloured, but equally 

 gaudy rays will be seen round it, probably 

 produced by the moving legs and by re- 

 fraction. 



