56 VERTEBRATA. MAMMALIA. 



its change. " But this," says Mr. Bell, and it is 

 a beautiful proof of Providential care, " is not the 

 most important advantage gained by the assumption 

 of the white clothing in the winter season. It is 

 too well known to require more than an allusion, 

 that although the darker colours absorb heat to a 

 greater degree than lighter ones, so that dark-colour- 

 ed clothing is much warmer than light-coloured, 

 when the wearer is exposed to the sun's rays ; the 

 radiation of heat is also much greater from dark 

 than from light-coloured surfaces, and consequently 

 the animal heat from within is more completely re- 

 tained by a white than by a dark covering ; the tem- 

 perature therefore of an animal, having white fur, 

 would continue more equable than that of one 

 clothed in darker colours, although the latter would 

 enjoy a greater degree of warmth whilst exposed to 

 the sun's influence. Thus the mere presence of a 

 degree of cold, sufficient to prove hurtful, if not 

 fatal to the animal, is itself the immediate cause of 

 such a change in its condition as shall at once nega- 

 tive its injurious influence."* 



Martes,^ the Marten. 



The Martens are closely allied to the Weasels, 

 but having an additional false molar, and a tubercle 

 on the inferior lacerator, they are rather less sangui- 

 nary. Distinguished in form by greater elegance of 

 contour, large open ears, and a long bushy tail, they 

 are marked also by habits more decidedly arboreal. 

 * Brit. Quad. p. 154. t Its Latin name. 



