COLORATION 127 



course, exceptions to these general rules, such as the musk- 

 ox, raven, and wolverene in the boreal realm, or the male 

 ostrich, black and white chat, lark-bunting, and various 

 black or advertisingly colored lizards, like the Gila monster, 

 in arid or semiarid lands. The rule is general, however. 

 We do not here discuss the interesting problem of the col- 

 oration of arctic animals. But in the arid and humid re- 

 gions referred to the prevalence and repetition of pale and 

 dark types is almost certainly due to the varying degrees of 

 sunlight and moisture. A consideration of certain forms 

 only would make it possible to contend that the coloration 

 was developed by natural selection for concealing purposes. 

 But there are other forms, to which it is not possible to 

 apply this theory, which nevertheless are also colored in the 

 same general manner. The pale desert antelopes, such as 

 the desert oryx, show what is simply a more extreme de- 

 velopment of the coloration already tending to develop in 

 their several kinds on the semiarid plains; they never hide; 

 and their lives are led under conditions which, as we have 

 shown in the case of the ordinary plains game, make it 

 absolutely impossible that any type of coloration can have 

 any survival value for them. In similar fashion, the black 

 duck-hawk of the Puget Sound region and the pale eagle- 

 owl of the Western American plains show each the general 

 type of coloration of the faunas of their respective localities, 

 and yet lead lives such that this coloration can in no way 

 help them to secure their prey. It may, therefore, be ac- 

 cepted as certain that the pale desert coloration is not pro- 

 duced by natural selection directed toward a concealing 

 coloration. It is possible that there exist obscure relations 

 between pigmentation and bodily health, which have se- 



