2o8 EVOLUTION, GENETICS, AND EUGENICS 



of color are concealed by having the upper surfaces dark, the lower sur- 

 faces light, and a blending of one into the other on the sides. Nearly 

 all birds of the open, such as sea birds and soaring birds, use this 

 method of concealment. The same is true for fishes that live near the 

 surface, and for many mammals that are likely to be seen against a 

 sky line. Actual demonstrations have shown that this method of 

 concealment is highly effective, no matter from what point of view the 

 animal may be seen. A third scheme is one that was used most effec- 

 tively during the war in concealing battleships, heavy artillery, and 

 other large objects, namely, destroying the continuity of outline by 

 using large, irregular patches of contrasting or light and dark colors. 

 In this way a broken, irregular patchwork of color takes the place of 

 a coherent, regular contour. It is probably in this way that many of 

 the most brilliant coral-reef fishes attain concealment. Instead of the 

 fish as a whole being the center of vision, the bright patches stand out 

 against the dark, and these fail to give any picture likely to be inter- 

 preted as a fish either by enemies or by prey. Professor Reighard in- 

 terpreted the brilliant patterns of reef fishes as examples of "immunity 

 coloration," the idea being that these fishes were so safe from attack 

 and so little in need of concealment from prey that they simply went 

 the Umit in color display, unchecked by natural selection. Longley 

 has recently shown that the patterns and colors of such fishes are in 

 reality obhterative, and if this be true, there is no need of introducing 

 the idea of "immunity coloration." 



In view of the above considerations, it now seems likely that essen- 

 tially all types of animal coloration that have any adaptive value at all 

 — and by no means all have any demonstrable adaptive significance — 

 may be classed under the general head of conceaUng coloration; and if 

 this be so, it greatly simplifies the problem of the evolutionist. Much 

 of the controversy as to the efficacy of natural selection has been waged 

 about some of the questionable categories of animal coloration, such 

 as "warning coloration," "mimicry," "confusing coloration," "sexual 

 coloration." If all of these turn out to be merely phases of conceal- 

 ment coloration, their origin could be explained as readily as that of 

 any other adaptive character of definite selective value. 



The Case of Kallima. — With this general introduction to the sub- 

 ject of animal coloration, it does not seem necessary to Hst examples of 

 all the categories of color mentioned. Let us close the discussion with 

 what appears to be the classic instance in biological Uterature of perfect 

 protective resemblance: that of the "dead-leaf butterfly," Kallima 

 (Fig. 41). 



