INTRODUCTION 



WHILE man has gone on wresting from Nature one deep-buried secret 

 after another, the whole field of protective coloration has lain un- 

 concealed, inviting recognition, resplendent with wonderful and beautiful 

 phenomena. Yet of these he has remained uncognizant, or caught only 

 fragmentary glimpses, piecing together the fragments with the aid of false 

 hypotheses, which have presented such a spectacle of inconsistency as to 

 bring the whole subject into widespread contempt. 



The entire matter has been in the hands of the wrong custodians. Apper- 

 taining solely to animals, it has naturally been considered part of the zoolo- 

 gists' province. But it properly belongs to the realm of pictorial art, and can 

 be interpreted only by painters. For it deals wholly in optical illusion, and 

 this is the very gist of a painter's life. He is born with a sense of it; and, 

 from his cradle to his grave, his eyes, wherever they turn, are unceasingly at 

 work on it, — and his pictures live by it. What wonder, then, if it was for him 

 alone to discover that the very art he practices is at full — ^beyond the most 

 delicate precision of human powers — on almost all animals? Fortunately, 

 although this search, like all others, requires a specialist, the beautiful things 

 discovered are appreciable by all men; and our book presents, not theories, 

 but revelations, as palpable and indisputable as radium or X-rays. 



Naturalists have not understood the principles of objects' distinguishability. 

 Let us first consider the part distinguishability plays in animals' lives. Sight, 

 in the great majority of cases, is the sense by which at the last moment the 

 quarry's fate is decided. Had the cougar, wolf, or fox no eyes, he would 

 starve. Had the hare no sight, he could not teU when to abandon his 

 squatting and spring away, or which way to dodge the murderous leap that 

 would follow. Scent brings the predator along the trail or up-wind nearly to 

 the game, but were this pursuer blind, he would seldom (except in 



3 



