Retrospective Criticism* 79 



further remarkable by their likeness to their mother; and so 

 great is their resemblance to each other, as to size and colour, 

 that a stranger cannot, for some time, perceive any difference 

 in them. — Jfowfs G. Tatem. Wycombe, Nov. 26. 1832. 



Changes in the Colour of the Coverings of Animals towards 

 Winter. — Sir, As Zoophilus, in his paper (Vol. V. p. 718.) 

 on the change of colour in the external covering of animals 

 and birds in winter, has not touched upon, what I consider, 

 the more important and obvious uses of this beautiful provi- 

 sion of nature, I trust he will not feel displeased if I offer a 

 short explanation of them for the information of your younger 

 readers, by way of rider. 



A white animal, or bird, upon the snow, is, doubtless, less 

 conspicuous, and consequently less exposed to danger from 

 its natural enemies, than in its ordinary costume. It is, there- 

 fore, quite legitimate to argue that this change is given to the 

 weaker and more defenceless tribes, for their protection ; 

 being somewhat analogous to the near approach we observe 

 in the colour of many birds and insects to that of the places 

 they commonly frequent. But the great polar bear, the arctic 

 fox, &c, can need no such aids; and ev^n Jtoejjpy weasel has 

 agility and courage enough to defend itself. Yet these also 

 are clad in the usual winter garb of high latitudes. And how 

 does the matter stand as to some aquatic birds, which also 

 assume a white, or a whiter, plumage in winter, but which 

 certainly are thereby made more conspicuous in their common 

 haunts, whether these be the dark surface of the water under 

 the lowering skies, and during the long nights of winter, or the 

 black rocky beach, between the high and low water-mark, 

 where snow cannot lie ? These exceptions, and others 

 which might be named, are, I think,, s,j$c^itly weighty to 

 render the argument untenable, and to induce us to search 

 elsewhere for a more philosophical and satisfactory explana- 



lhat the changes in question are chiefly, it not solely, 

 influenced by a great diminution of ordinary temperature, is 

 proved by their being more or less rapid, as well as more or 

 less complete, in proportion to the t ^ariv i or* -iatp approach of 

 cold, as well as to the degree of its intensity. Many instances 

 of these modifications are on record, and they strongly sup- 

 port the view I have taken, namely, that this change from the 

 usual colour to white is primarily designed to protect the 

 animal from the severe cold to which, from its locality, it is 

 necessarily exposed, and which, without some such provision, 

 the structure of its organisation could not withstand. And 

 here, as everywhere in nature, we see cause and effect.mutually 



