496 Allen, The Concealing Coloration Question. [oct. 



by his prejudices. It is evident, I think, that we cannot accept 

 Roosevelt's conclusions without careful examination, and equally 

 evident that Thayer's testimony, expert though it is, must be 

 weighed in the judicial balance before we can know how much it 

 is worth. And it is for scientific men to make the examination 

 and do the weighing, not for artists nor for hunters. I do not, 

 of course, propose to attempt to settle the question myself. I am 

 simply going to try to draw the lines a little more clearly, — to 

 whistle up a breeze that shall blow away some of the dust and 

 smoke that have settled down over the field, so that the issue may 

 be seen more distinctly. 



In the first place, then, what is Mr. Thayer's main contention? 

 It is stated in the Introduction to his book as follows : " The colors, 

 patterns, and appendages of animals are the most perfect imagin- 

 able effacers under the very circumstances wherein such effacement 

 would most serve the wearer. For any animal to be seen looking 

 conspicuous means no more than that he is not at those moments 

 looked at under the circumstances for which his concealing-colors 

 are effective." ^ Obviously it is impossible to prove this general 

 statement in particular. No one knows enough of the conditions 

 of the lives of all animals to do so. I think Mr. Thayer is justified, 

 however, in his contention that if his conclusions are found to be 

 reasonable in an overwhelming number of cases, it is only fair to 

 give him the benefit of the doubt in those remaining cases where 

 proof is more difficult or even impossible with our present knowl- 

 edge. Of course, if it can be proved that these hypothetical 

 exceptional cases are not cases of concealing coloration, that will 

 settle the question so far as the existence of a universal law is 

 concerned; but it is notoriously hard to prove a negative. I mean 

 by this that Thayer is not called upon to explain the coloration 

 of every single species of bird or mammal. If we find his theory 

 true in the main, we can accept the doubtful cases on faith. That 

 is what we have done with the evolutionary theory. It is not 

 necessary to account for the development of every species by 

 natural selection or any other means. We believe in the theory 

 in spite of the inexplicable cases. It must be admitted, however, 



I Op. cit., p. 9. 



