618 Correspondence. [bet. 



CORRESPONDENCE. 



Naturalists and ' Concealing Coloration.' 



Editor of 'The Air.' 



Dear Sir; — In a Utter just received from Mr. John T. Coolidge 3rd. 

 now in British Easl Africa, he writes: "What you say about an object of 

 uniform color against the sky seen from below has been impressed upon 

 me lately. I tind that in hiding to ambush game for moving pictures, it is 

 essential to have an opaque background, otherwise you are sure to be 

 detected, silhouetted against the sky. 1 am going to pin white strips of 

 paper on my shoulders and helmet, when an opaque background is not 

 obtainable. 



I am doubtful about getting a Chapman's Zebra, but shall not fail to 

 bring you a Grant's Zebra. Individuals vary tremendously but many 

 Grant's Zebra have jet black snipes on a elean white ground. Rarely 

 they have a faint supplementary stripe between the others and sometimes 

 the stripes are brown on a yellow-cream ground, but I will look for a 

 COntraety one. I have moving pictures of Zebra coming to water 

 which show the extreme fear they have of approaching the bushy and 

 reedy water holes, even by day. In the rains, they can drink out of pans 

 in the open, but all permanent water is surrounded by bush or reed-, or 

 usually both. * * * " 



This should remind the reader of the obviousness of what 1 have re- 

 peatedly tried to show to naturalists, that the laws o\ illumination and 

 vision are the same the world over, and that the naturalists who have 

 opposed the progress ^i thi- great biological discovery merely need to 

 study these laws. 



This well known variation of zebras' colors from black and white to 

 brown and yellow is absolutely parallel to the variations of form and other 

 Characters, equally well known in almost all species. All the eases are more 

 or less obviously traceable to corresponding variation in the animals' cir- 

 cumstances. 



In the Zebra's ease, for instance, pure black and white are a little the 

 best costume where the sky. and particularly stocky (and therefore par- 

 ticularly opaque) reeds tend to ho the animal's sole background. On the 

 other hand, in a region where more translucent vegetation and less open sky 

 are typical, so that the lightest note behind the zebra is apt to be mere 

 lighted foliage oftener than sky, a brown and yellow zebra would often 

 match a little closer than a black and white one. 



Yours very truly. 



Abbott H. Thayer. 

 Nfonadnock, N. H. 

 Sept. 11. 1913. 



