THE oKicix or (jRorsi:. -ox 



other northern animiils have done ; for in a umToiin 

 white surface any variation of colour is far more certain 

 to be spotted and cut off than in a inany-colouretl and 

 (hversifietl environment. I'hus it would seem probable 

 that the Scotch j^rouse has slowly become accommodated 

 to the heather, amoiiL^ which it is so hard totliscover it ; 

 while the willow-^M'ouse has ^rtnvn to reseml)Ie the snow 

 in win'^.r, anil the barer grounds of its northern feeilinj^^- 

 l)laces in the short Scandinavian ami Icelandic summer. 

 If this be so, we must reijanl both birds as sliL^htly 

 tliverj^ent descendants of a common ancestor, from 

 which, however, our grouse has varied less than its 

 Continental convener. Of course, it is just possible that 

 the common ancestor had already accjuired the habit of 

 changing its coat in winter before the divergence took 

 place ; and if so, then it is the Scotch <;rouse which has 

 altered most : but this is less probable, because the use- 

 fulness of the chani^e would certainl)' be felt even in a 

 Scotch winter, and the white suit is not, therefore, likely 

 ever to have been lost when m ce accjuired. Though 

 the winter is not severe enouLjh in Scotland to make 

 such a chan<,rc of coat inevitable where it does not 

 already exist, it is yet quite severe enou^^h to preserve 

 the habit in animals which have once acquired it, as we 

 see in the case of the varying hare, a creature which in 

 colder ages spread over the whole of northern Europe, 

 and which still holds its own among the chillier portions 

 of the Scotch Highlands, Hence we may reasonably 

 infer that if our grouse had ever possessed a winter coat 

 it would have always retained it for an alternative dress, 

 as the ptarmigan still does in the self- same latitudes. 

 Accordingly, analogy seems to point to the conclusion 



