A Substitute for the Theory of Warning Coloration. 319 



The liberty to indulge in the striking colors developed in the garter snakes of this 

 region is partly due to the protection afforded by abundant vegetation, and perhaps in 

 some degree to the absence of the three snake-eating genera, Spiloles, Ophibolus, and 

 Elaps. 



All these classes of cases may be brought under the head of immu- 

 nity coloration and iTiay be attributed to inaccessibility. There are doubt- 

 less many other similar cases to be found in the literature and many cases 

 of conspicuousness in insects now attributed to unpalatability may be due 

 to other conditions. That other circumstances than unpalatability and in- 

 accessibility may condition immunity coloration is probable. 



Immunity coloration may now be defined as " coloration, not sexually 

 dimorphic, which renders an organism in its natural environment conspicuous 

 to vertebrates ; zchich lias no selective value, since it does not aid the organism 

 in escaping vertebrate enemies by concealment (protective coloration), nor 

 in approaching its accustomed invertebrate prev (aggressive coloration), and 

 when associated zcith disagreeable qualities is unnecessary as a zvarning to 

 vertebrate foes of the existence of such qualities (zvarning coloration) ; it is 

 conceived to have arisen through internal forces under immunity of the organ- 

 ism from the action of selection on its color characters." The exclusion of 

 all sexually dimorphic coloration from the definition is provisional. 



The obvious relation usually observable between completed aniinal char- 

 acters and their function or utility is reflected in the curious anthropomor- 

 phic feature of those modern theories of evolution that are founded on a 

 relation between the evolution of these structures and utility. This view- 

 point finds interesting expression in theories of animal coloration. Sexual 

 coloration, warning coloration, and possibly recognition marks may have 

 obvious, though perhaps not necessary, uses ; their evolution is therefore 

 assumed to have taken place in relation to these uses. The utmost in- 

 genuity has been exercised to discover plausible utility in every fieck of 

 color with the conviction that thereby evidence was being accumulated 

 as to a mode of evolution. The theory of orthogenesis alone is free from 

 this limitation, since it holds that characters may arise and be without 

 utility or their utility be determined afterward. The present paper holds 

 that immunity coloration has developed in no relation to utility, but it 

 does not discuss the method of that development. The view is presented 

 as a working hypothesis which it is hoped soon to further test. 



