42 The Life Story of the Fish 



the third, a specimen about ten inches long, I was, in spite of 

 all my efforts, unable to catch. I knew the rock under which 

 he lived, and I saw him several times. I pricked him once, 

 and after that he never came near the hook. Finally, much 

 against my will, I placed a trap in the stream for him. The 

 next morning there were six ten-inch trout in the trap. In 

 spite of the fact that I had watched that short stretch of 

 stream, not over thirty feet long, and nowhere more than 

 two feet deep and eight feet broad, steadily throughout a 

 whole month, I had never seen more than one fish in it, and 

 him only rarely. 



No protective motivation has been discovered for the spec- 

 tacular changes in color and pattern which some of the coral 

 reef fishes go through. Species are known which have at least 

 seven distinct costumes which they change with almost un- 

 believable rapidity. The transformations appear to be con- 

 nected with emotional or physiological disturbances. Why 

 this should be so, or its value, is not known j but that chro- 

 matophores furnish the mechanism is recognized. 



Aside from color-change by means of chromatophores, at 

 least two other general types occur in fish. One is the intensi- 

 fication of coloring and the addition of brighter colors which 

 accompany spawning — the so-called "nuptial coloring." 

 This occurs most frequently in fresh-water species, and is 

 rarely found in salt water. It Is conspicuous in the primitive 

 "bowfin" of our Middle West and in some of the trouts. It 

 occurs to a certain extent among the sunfishes and black 

 basses. Very little attempt has been made to find out the 

 machinery of these changes, but it may be deduced from 

 what is already known that chromatophores play no large 

 part, and that the effect is due to the general excitement of 

 the fish — for even human beings are brighter colored when 

 in love — and to an addition of bright pigment to the perma- 



