334 THE REDISCOVERED COUNTRY 



concealing coloration theory. The Thayers elaborated 

 this theory to its last conclusions in a thick volume and nu- 

 merous pamphlets. Certain naturalists, Colonel Roosevelt 

 the most conspicuous among them, criticised the theory and 

 its application. The ensuing discussion reached its greatest 

 height between my two African trips. Therefore I went on 

 this last journey with all data freshly in mind. Both 

 Cuninghame and myself were throughout the whole time in 

 the field keenly alert to prove or disprove — in our own 

 minds — the contentions of both parties. It might further 

 be pointed out that at the start we were neither of us 

 partisan for either side of the discussion; that we are both, 

 in a sense, trained observers; and that we had here unrivalled 

 opportunities for studying tens of thousands of animals in 

 undisturbed country. In order to define my position 

 clearly at the outset, I will state that in general I hold 

 with Colonel Roosevelt, and unqualifiedly advise the reader 

 to peruse his chapter on this subject in " Life Histories of 

 African Animals." What follows is intended merely to 

 call attention to certain phases. I believe most of these 

 to be of optical rather than evolutionary value. 



The only points which seem to me important in Mr. 

 Thayer 's contention are these : 



1 . The theory of counter-shading. That is to say, most 

 animals are coloured lighter underneath than on top in order 

 to compensate for the shadow cast by the animal's body. 

 The net result is supposed to be a monochrome. 



2. The theory of night blending. A great many beasts 

 are conspicuously white somewhere on the upper body line. 

 The tails of white-tailed deer or prong-horned antelope are 



