in which Changes of Colour aye effected in Moulting. 307 



species, in a captive state, are much slower in acquiring the 

 adult colours than when in their native wilds ; wherefore, it 

 may be presumed that locality and circumstance may some- 

 times exercise a very considerable influence in accelerating 

 or retarding, in hindering or otherwise modifying, the attain- 

 ment of typical perfection. At the same time, we must not 

 forget the aggregate of difficulties which every species has to 

 encounter when occurring beyond the sphere of its adapt- 

 ations, and which rarely permit of its maintaining a prolonged 

 existence elsewhere than in its normal habitat, where all alike 

 conduces to its security and welfare. 



However, some of the facts above mentioned quite warrant 

 us in suspecting (what, indeed, proves to be the case) an occa- 

 sional variation in the mode in which the seasonal changes of 

 colour in the clothing of animals are brought about, even in 

 the same species, when under the influence of diverse circum- 

 stances. It would seem that the effort of nature, in most 

 instances, was to throw off and renew the covering ; but that 

 this tendency is susceptible of being modified, or even coun- 

 teracted, not only by specifical peculiarity, but by the relative 

 amount of constitutional vigour in different individuals of the 

 same species; intermediate gradations obtaining, probably, in 

 both instances, analogous to what have already been described. 

 The effects of confinement in obstructing regular natural 

 changes are manifested in a variety of instances : thus, the 

 common squirrel, which, in the wild state, renews its fur in 

 spring, obtaining a much coarser and redder coat, and, at the 

 same time, losing the ornamental long hairs which, in winter, 

 adorn its ears, rarely exhibits even an indication of this 

 change when in captivity ; and it is well known that the linnet 

 tribe, when under the restraint of the cage, display not the 

 slightest trace of those seasonal brightenings, which so re- 

 markably distinguish these birds in a state of freedom. In- 

 deed, in the latter instance, as the linnets breed prolifically 

 in confinement, we can hardly assume that physical weakness 

 is the cause of this ; and it becomes difficult to assign to what 

 external influence their summer brilliancy may be attributable, 

 or, rather, to determine the reason of its suppression in vigorous 

 captive specimens. 



The bleaching of cuticular productions by severe cold can 

 hardly be esteemed analogous to other alterations of colour ; 

 neither does it seem to be more akin to those sudden changes 

 of the human hair to grey, which have happened during 

 continued intense emotions of fear or anxiety. It is, how- 

 ever, difficult to assign to what extent the changes of arctic 

 animals are dependent on external influence ; for though, in 



