TROUT FLY-FISHING IN AMERICA 



The most vivid coloration of trout, on the other hand, 

 is produced by the darker and more brilliant pigment col- 

 ors which are contained in the cells located in the skin un- 

 der the scales. 



The activity of the pigment cells is the factor which 

 causes the many and rapid changes of coloration to take 

 place. 



The character of the water bottom, 

 The kind or degree of light, 

 The breeding season, and, 

 The age of trout, 



all play important parts in influencing activity by caus- 

 ing expansion and contraction of the pigment cells, which 

 in their turn increase or decrease the accumulation of 

 the pigment colors in the cells. 



The pigment cells, so far as coloration is concerned, 

 are rendered most active when subjected to the influences 

 of a light water bottom, bright light, clear and shallow 

 water; they are rendered least active when subjected to 

 the influences of a dark water bottom, dull light, muddy 

 and deep water. 



The activity of the pigment cells remains relatively the 

 same as a general proposition throughout all seasons so 

 far as the influence of these conditions alone is concerned. 



The activity of the pigment cells is still further influ- 

 enced and intensified by the breeding season because it is 

 during this period that the nervous system of trout is most 

 sensitive. 



The age of trout also exerts some influence upon the 



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