Vol.XXVIII 

 1911 



Allen, Roosevelt on Concealing Coloration. 479 



those who witnessed it were profoundly impressed and somewhat 

 startled by what they witnessed. It was easy to recognize that 

 Mr. Thayer had discovered a hitherto overlooked principle in 

 optics which seemed to explain how the white underparts of 

 terrestrial birds and mammals rendered them protectively colored. 

 If objects like sweet potatoes suspended a few inches above the 

 ground on a green lawn could be rendered invisible by painting 

 their lower surface white, such markings on the ventral surface of 

 animals must, it would seem, tend to their concealment. But 

 when we come to study such animals in life it becomes apparent 

 that their manner of living greatly qualifies its effectiveness for 

 their concealment, especially in short-legged and crouching animals 

 that live on the ground. Later, however, Mr. Thayer extended 

 his experiments to the pattern markings of animals, and with arti- 

 ficially constructed backgrounds, or with favorably chosen natural 

 backgrounds, was able to demonstrate the practical disappearance 

 of animals with color patterns. This was all very striking and 

 very interesting, and very few who witnessed his demonstrations 

 reflected that the effects were produced through artificial environ- 

 ment, and really proved very little as to the effect of color patterns 

 as a means of concealment in living animals in the actual or natural 

 environment of the species. It showed possibilities that might 

 never happen in life, or so rarely as to be negligible as a means of 

 protection at even vital moments in an animal's career. Discov- 

 ery of the possibility of finding backgrounds that will match the 

 coloration of any or of every bird or mammal when motionless does 

 not necessarily have an important bearing on protective coloration 

 in animals, as has been well-shown in Mr. Roosevelt's illuminating 

 paper. It is here that Mr. Thayer has been misled in his later 

 investigations, as shown in his book on Animal Coloration and in 

 his later papers in reply to his critics. This is unfortunate and to 

 be greatly regretted, for only personal friendship has deterred 

 many of his friends who differ from his conclusions and believe his 

 methods of proof are seriously defective, from openly assuming the 

 role of critic. For him to say he is misunderstood by his critics, 

 and that they do not agree with him because they do not under- 

 stand the ' laws of optics,' is a lame defense for the misconceptions 

 with which his book and recent papers abound. 



