TROUT FLY-FISHING IN AMERICA 



Character of the water bottom : 

 {External factor) 



Kind or degree of light; 

 (External factor) 



The function of this factor is ef- 

 fectively and directly to influ- 

 ence at all times the many 

 changes of coloration that take 

 place. 



The function of this factor is to 

 control the coloration of trout 

 through its influence upon the 

 water and the water bottom. 



The position of the pigment cells is the factor in trout 

 coloration which renders the cells sensitive and suscepti- 

 ble to the influences which make it possible for the many 

 changes in coloration to take place. 



The pigment cells are located in the skin and on or 

 near the surface of the scales, and this holds true with all 

 species and sub-species of trout wherever found. 



The number of pigment cells, their size and the kind 

 of pigment colors, however, vary greatly with the differ- 

 ent species which, in a large measure, accounts for their 

 marked differences in coloration. 



The silvery and golden hues of coloration are made 

 so very pronounced because the pigment colors producing 

 them are contained in cells located on or near the surface 

 of the scales and therefore are more easily and quickly 

 influenced than are the skin cells. 



Bright, white sandy bottoms under bright light, with 

 clear, shallow water, bring out to the greatest extent the 

 silvery sheen on trout, while bright, yellowish sandy bot- 

 toms under the same conditions of water and light bring 

 out to the fullest extent the golden luster. 



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