1912 J Allen, The Concealing Coloration Question. 497 



that the theory of evolution stands on a somewhat different footing 

 from that of conceahng coloration, in that it is in its very nature 

 a universal one, while to account for coloration there may be 

 several theories which are not mutually exclusive. In fact, there 

 seems to be no good a-yriori reason for seeking a universal law for 

 coloration. The old theories, of protective coloration, sexual 

 selection, mimicry, warning colors, directive markings, etc., have 

 long been considered satisfactory enough. If, however, there 

 actually is such a universal law as Thayer asserts, we must come 

 to accept it in the end. It remains to learn the facts. 



I need not go into the various methods by which, according to 

 Mr. Thayer, concealment is brought about, — counter-shading, 

 background-picturing, ruptive and secant patterns, masking of 

 eyes, bills and feet, iridescence, appendages, etc. It may be taken 

 for granted that my readers are familiar with the main principles 

 as enunciated by him. Let us turn at once to Colonel Roosevelt's 

 conclusions and see just Avherein they differ from Thayer's. In 

 the first place, then, he refuses to accept the theory of natural 

 selection as accounting for such concealing coloration as he admits 

 to exist. He says it is possible that the tendency towards conceal- 

 ing coloration is the result of natural selection, but to his mind 

 much more probable that the major part of the tendency is due 

 to the effect of physical surroundings upon all the individuals of a 

 species.^ This theory has, of course, been held by many, but 

 though moisture and dryness, heat and cold, and diet, all doubtless 

 do have an effect in certain cases, as Mr. Beebe has proved, for 

 instance, in his experiments with birds in captivity, it is in the 

 main a vague and unsatisfactory theory, since it cannot show the 

 method by which such changes are brought about. To most 

 of us, I think, the theory of natural selection seems the most 

 reasonable explanation of most of the facts of evolution. Whether 

 or not Roosevelt's doubts about it are due to a difficulty in recon- 

 ciling his ideas of advertising coloration with it, he does not state, 

 and we can only conjecture. 



Here, then, is one distinct issue, — a belief in natural selection, 

 which, of course, Thayer believes to be universal and Roosevelt 



1 Revealing and Concealing Coloration in Birds and Mammals, p. 212 (1). 



