328 AFFINITY BETWEEN GREAT HEAT AND GREAT COLD. 



when the great cold passed away and spring returned, 

 these animals gradually resumed their normal yellowish 

 colour, and white hares disappeared. In the London 

 game dealers' shops in spring, many Russian hares are 

 as we have mentioned exposed for sale, partly, or even 

 entirely, of a white colour; but on enquiry into this 

 matter when in Russia, we were given to understand 

 that hares always turned more or less white there 

 every winter, and changed colour again in spring. The 

 case of the hares in Ireland in 1878, which was 

 there regarded as unparalleled, is therefore an event 

 of annual occurrence in Russia, and also we believe in 

 Norway and Sweden. Then as regards birds, the 

 ptarmigan, of which we have been speaking, is known 

 in Scotland to be mostly of a brown colour, like 

 ordinary heather grouse, in summer, but to assume its 

 snowy garb on the approach of winter. These con- 

 siderations, as we believe, fully justify us in regarding 

 the universally white colours seen among arctic birds 

 and animals as due entirely to the rigour of the 

 climate, and that it is by this means that Nature effects 

 these changes; though we do not deny that the 

 interbreeding of animals, etc., of this colour, during 

 long periods of time, may also have had its effects 

 in rendering the white colour more pronounced and 

 snow like; and possibly if some of these creatures 

 would bear transportation to a southern climate, it 

 might be found that this colour had become permanent 

 in the case of some of them: a white bear cub for 

 instance, brought to a zoological garden, always 

 remains, not white, but yellowish-white. 



The effects of great cold are so peculiar and remark- 

 able that to those who have never experienced any- 



