338 



SCIENCE. 



[Vol. IV., No. 87. 



course, are very significant, and can only be 

 explained as being serviceable to the fishes in 

 rendering them inconspicuous, both to their 

 enemies and to the wandering animal-life on 

 which they prey. In precisely what way the 

 extreme variations from very dark to pale are 

 serviceable, is not yet known, so far as I am 

 aware ; but the fact itself can scarcely be used 

 to the disadvantage of the main proposition, 

 that the color and its changeableness are of 

 benefit to the fish, and are under the animal's 

 control. 



I think we have, in the fact that usually they 

 deposit their ova and milt in rapid waters. 

 Waters with a constantly rippling and troubled 

 surface certainly protect them from such ene- 

 mies as the kingfisher, fish-eating mammals, 

 and probably from frogs and snakes. By draw- 

 ing a seine through turbulent water at the 

 foot of a mill-dam, I have frequently found 

 scores of splendidly colored cyprinoids ; and 

 finally, very soon after spawning, all these 

 extra tints facie out utterly, and the fishes 

 return to their accustomed haunts. These facts 



Banded sun-fish (Mesogonistius chaetodon). 



During the early spring, when the vigor of 

 these fishes is at its maximum, the coloration is 

 more pronounced in every particular ; and the 

 continual changing from dark to light, and vice 

 versa, as seen in connection with its other 

 habits, shows plainly that it is as much under 

 control as are the folding and spreading of a 

 peacock's tail. 



The c}'prinoids, or ' shiners,' known collec- 

 tively as minnows, roach, and dace, so many 

 species of which are conspicuously colored at 

 least at one time of the year, are all essential- 

 ly diurnal in habit. Their bright colors, as a 

 sexual attraction, are essential to their welfare, 

 but are, at the same time, detrimental to their 

 safety. Have we any reason for believing that 

 these fishes seek to avoid exposure to enemies 

 when thus arrayed in extra-conspicuous dress? 



certainly seem to indicate that they are aware 

 of the disadvantage of unusually bright colors, 

 which, notwithstanding, are essential to the 

 perpetuation of their kind. 



The common banded sunfish (Mesogonistius 

 chaetodon), a silvery- white species, has a re- 

 markable control over the color of the black 

 vertical bands that ordinarily form so conspicu- 

 ous a feature of the fish. At times when the 

 water is rather clear, and the amount of vege- 

 tation not abundant, this sunfish will fade out, 

 and show such ashen, faintly streaked sides, 

 that it might almost pass for a dead leaf; but 

 roused to action by the approach of other fishes, 

 or the finding of food, the dull sides glisten 

 like polished metal, and the faint bands be- 

 come as black as ebony. Certainly these great 

 and sudden changes are not involuntary. They 



