TROUT FLY-FISHING IN AMERICA 



case with fish that are found in caves where but little light 

 ever enters. 



Therefore the effectiveness of light so far as kind or 

 degree is concerned must necessarily depend upon three 

 external elements : 



The kind of day, 



The condition of the water, 



The season of the year. 



The best or greatest coloration can only be produced 

 when the highest degree of light is made most effective 

 upon a light water bottom, and the poorest and least col- 

 oration when the smallest degree of light is made ineffect- 

 ive upon a dark water bottom. 



Between these two extremes we have the normal or av- 

 erage coloration of trout except just before and during 

 the breeding or spawning season. 



Bearing of Factors Upon Coloration 



Position of the Pigment Cells 

 {Internal Factor) 



[Skin cells contain the dark pigment colors. 

 ^ * I Scale cells contain the light pigment colors. 



Character of the 



water bottom: 

 {External factor) 



Kind or degree of 



light: 

 {External factor) 



Activity of the Pigment Cells 

 {Internal Factor) 



Light bottom, bright coloration. 

 Neutral bottom, subdued coloration. 

 Dark bottom, dark coloration. 



Bright light, bright coloration. 

 Subdued light, subdued coloration. 

 Dull light, dark coloration. 



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