THE COLORATION OF REEF FISHES 555 



Correlation of color with habit 



When it stands alone, the inconspicuousness imphed by the 

 occurrence of countershading is insufficient to force the abandon- 

 ment of current explanations of the significance of bright colors; 

 for once grant that there are 'conspicuous' animals, and it is 

 incontestable that in a species springing from an inconspicuous 

 line countershading, having outlived its usefulness to the ances- 

 tral type, may persist as a vestigial character. But when coun- 

 tershading and adaptive color change are coupled with one 

 another, as they are in many highly colored species, the pressure 

 brought to bear upon the hypotheses which assume that certain 

 types of coloration must be conspicuous is greatly intensified, for 

 the interpretation naturally placed upon the two phenomena is 

 the same, and is opposed to this conception. The second, more- 

 over, can scarcely be explained as a survival from another age, 

 for its manifestation depends upon the efficient cooperation of 

 several of the most highly differentiated organs or organ systems 

 in the body. Yet the facts of adaptive color change are not of 

 general application to bright colored animals. Hence it is 

 difficult to exaggerate the importance of a successful attempt to 

 discover a rational system of distribution of the colors themselves, 

 which the different species wear, and with which countershading 

 and adaptive color change are associated. 



If the attempt to define such a system should fail, it is still 

 possible that the creatures are as inconspicuous as may be under 

 the conditions in which they live. If, upon the contrary, the 

 effort should be successful, and a consistent relation between 

 color and habit be demonstrated, such that conspicuousness 

 might thereby be supposed to be reduced to a minimum, the 

 uniform suggestion flowing from this fact and from countershad- 

 ing and adaptive color change will constitute as strict proof of the 

 concealing function of color as may be had, short of unimpeach- 

 able feeding experiments. 



The first attempt to determine whether the reef fishes repeat 

 the colors of their en\dronment, as the Sargassum fauna does, 

 was made by analyzing their patterns and listing the few shades 

 that stand out at a distance of feet, rather than the great variety 



