PRINCIPLES OF PROTECTIVE COLOURATION 215 



for those appendages and ornaments, such as crests, manes, 

 tail feathers, long ears and plumes, which, seen against an 

 unusual background, seem expressly designed to be con- 

 spicuous. The law at work here is, indeed, sometimes very 

 close to that of mimicry. Thayer's contention, however, is that 

 protection is given not by the whole animal disguising itself as 

 an inanimate object but by some, so to speak, outlying portion 

 of it, by its resemblance to a natural object, drawing attention 

 away from what makes the whole animal recognisable, namely, 

 its outline. The two black ears of a white hare may be con- 

 spicuous enough against the snow but their very obviousness 

 helps to detract attention from the shadowy body which exactly 

 matches its background. Again, a hanging fringe of feathers 

 may be useful as a substitute for or an adjunct of countershading 

 to conceal the dark shadow on a bird's breast when it is standing 

 erect. Iridescent colours too, by their very brightness, blind the 

 observer to the shape which produces them and blur its outline. 

 In brief, the principle of the obliteration of the outline is that 

 which, of all Thayer's assumptions, is perhaps the most revolu- 

 tionary in the working out. To grasp it is to feel that the whole 

 problem of colouration has never before been approached from 

 a standpoint which so simply explains so much. It seems to 

 reveal, in the rigorous machinery of the law of natural selection, 

 an instrument of rare efficacy for the preservation and exten- 

 sion of a system of artistic obliteration incomparably delicate 

 and subtle. 



Thoroughly to understand that system it must also be 

 remembered that the protective schemes of the animal creation 

 have very seldom been elaborated to hide them from man. It 

 does not follow because the white rump of the antelope is con- 

 spicuous to a man on horseback who sees it against the ground, 

 that it is equally so to the wolf who sees it against the sky. 

 Though Thayer considers it incontestable that animals see 

 Nature, broadly speaking, with the same eyes as does man, no 

 one can maintain that they see it from the same angle. Thus, 

 since there is no such thing as " complete intrinsic incon- 

 spicuousness," the only way to appreciate an animal's means of 

 concealment is to learn to see it (and this, according to Thayer, 

 is what the ordinary naturalist cannot do) against its normal 

 background and from the position and angle of its most 

 dangerous enemy or favourite prey. 



