'* AXDIAL COLOKATION. 



ure offered hy the raveu oa the one liaiiJ and the Arctic fox 

 on the other ; it does undergo a certain amount of change at 

 the beginning of winter, becoming not white, but greyer. 



.Sometimes closely allied forms show a diifereuce in their 

 susceptibility to these climatic changes. One species of hare 

 turns white in the winter, another does not. 



The Hudson's Bay lemming (C'uniculus torquatus) under- 

 goes the change of colour, Imt its near relation the Scan- 



Fig. 1. -Arctic Fnx. 



dinavian lemming {Mijo.l.s lemmas) does uot undergo this 

 change. The principal animals which change to white in 

 winter, in addition to those already referred to, are the 

 ptarmigan, the American hare {Lepus amencamis), the ermine 

 and stoat. Witli regard to the Arctic fox (Cams hcfopns) it 

 has been stated* that this animal does not alter its colour 

 according to the season, and that the change is merely a 

 ^iuestion of age and sex ; only the old males are white, and 

 Trouessart," Xr( dcognipln,' Zoologiqiir;' Paris, 1800, p. id. 



