A Substitute for the Theory of JJ'aruing 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, Spilotes, Ophibolus, and 

 Elaps. 



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

 nity coloration and may 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, zdiich renders an organism in its natural eniironincnt conspicnoits 

 to vertebrates ; zvhich Ims no selective value, since it docs not aid the organism 

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

 in approa-ching its accustomed invertebrate prey {aggressive coloration), and 

 when associated zvith disagreeable qualities is unnecessary as a imrning to 

 vertebrate foes of the existence of such qualities (learning 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 animal 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 fleck 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. 



