50 MIMICRY, AND OTHER PROTECTIVE 



The desert birds are still more remarkably pro- 

 tected by their assimilative hues. The stonechats, the 

 larks, the quails, the goatsuckers and the grouse, 

 which abound in the North African and Asiatic 

 deserts, are all tinted and mottled so as to resemble 

 with wonderful accuracy the average colour and as- 

 pect of the soil in the district they inhabit. The 

 Rev. H. Tristram, in his account of the ornithology 

 of North Africa in the 1st volume of the " Ibis,'* 

 says : "In the desert, where neither trees, brush- 

 wood, nor even undulation of the surface afford the 

 slightest protection to its foes, a modification of colour 

 which shall be assimilated to that of the surround- 

 ing country, is absolutely necessary. Hence without 

 exception the upper plumage of every bird, whether 

 lark, chat, sylvain, or sand-grouse, and also the fur 

 of all the s,,ialler mammals, and the skin of all tJie 

 snakes and lizards, is of one uniform isabelline or 

 sand colour." After the testimony of so able an 

 observer it is unnecessary to adduce further exam- 

 ples of the protective colours of desert animals. 



Almost equally striking are the cases of arctic 

 animals possessing the white colour that best con- 

 ceals them upon snowfields and icebergs. The polar 

 bear is the only bear that is white, and it lives 

 constantly among snow and ice. The arctic fox, the 

 ermine and . the alpine hare change to white in 

 winter only, because in summer white would be 

 more conspicuous than any other colour, and there- 

 fore a danger rather than a protection; but the 



