2o6 EVOLUTION, GENETICS, AND EUGENICS 



Much has been written about these various categories of animai 

 coloration nearly all of which assumes some special adaptive value for 

 each type of color or pattern. 



The above classification is typical of the older views as to animal 

 coloration in that it recognizes no colors as merely incidental by- 

 products of metabolism, but assumes that all colors are valuable as 

 adaptations. Modern critics ar^ inclined to consider that at least 

 many colors are to be explained as the result of the fact that certain 

 chemical materials are formed in the elaboration of tissues and in the 

 physiological processes that must go on in these tissues, which, because 

 of their light-absorptive properties, appear to our eyes as colored. 

 The color may chance to enhance the protective resemblance of the 

 animal or it may make it more conspicuous than it should be; in either 

 case it may have an incidental value. But colors may come and colors 

 may go irrespective of adaptive value, for many colors are so placed 

 in the organism that they can never be visible; and color is only in 

 the seeing. While we have no intention of denying the adaptive value 

 of animal colors, it seems wise to get away from the extreme anthro- 

 pomorphic interpretation of these colors, for some of the categories of 

 coloration listed in the previous paragraph are largely, if not wholly, 

 anthropomorphic. It has been the habit of students of coloration to 

 assume that insects, birds, lizards, and other animals see colors and 

 patterns as man sees them, that what is attractive to man must also 

 be attractive to the lower animals, that what is confusing to man would 

 also be confusing to a lizard or an owl. Experiments with lizards, 

 which are supposed to be chief among the factors giving adaptive sig- 

 nificance to insect coloration, have shown that the lizard apparently 

 takes no notice of colors, at least when they are at rest, but will jump 

 at any moving object of about the right size. 



Modern students are inclined to think that many of the minor 

 categories of animal coloration listed above are, at best, of very ques- 

 tionable significance and that practically all categories simmer down 

 to one: obliterative coloration or camouflage. 



"All naturalists," says G. H. Thayer,' "perceive the wonderful 

 perfection of the twig mimicry by an inchworm, or of bark by a moth, 

 or of a dead leaf by the Kallima butterfly. It is now apparent that 

 almost equally marvelous concealment-devices, in one shape or 

 another, are general throughout the animal kingdom; the most gorgeous 



■ G. H. Thayer, Concealing Coloration in the Animal Kingdom. The Macnaillan 

 Company, 1918. 



