COLOURS OF MAMMALS 



hibernates. They do not remain for hours in a motion- 

 less condition save when asleep. 



So far as external characters are concerned the above 

 observations embody the principal points in which 

 the group differs from those of vertebrates lying lower 

 in the series. There are, however, still remaining, a few 

 characters which are highly noteworthy among the 

 mammalia without being absolutely diagnostic. It 

 will be readily observed in reviewing the large series of 

 mammals at the Zoo, and comparing them with the 

 larger series of birds, that the mammalia for the most 

 part are clad in a sober livery. There is nowhere in the 

 group that development of brilliant primary colours 

 such as we see so very commonly among birds. There 

 are no reds, greens and blues, the utmost brilliancy of 

 hue being bright browns contrasting with white, and 

 a few brighter colours, not of hair, but of naked skin, 

 such as the muzzle and ischial callosities of some monkeys. 

 If may be that correlated with this absence of striking 

 coloration is the predominance of the senses of smell 

 and hearing over sight. It is broadly true of the 

 mammalia, that they smell and hear rather than see. 

 While of birds it is equally true to say, that they see 

 rather than smell. That this point of view is in the 

 main correct is shown by another very characteristic 

 feature of the mammalia. In various parts of the body 

 glands open on to the surface ; these glands produce 

 variously smelling secretions, of which musk, civet, and 

 castoreum, are examples. The odoriferousness of the 

 houses in which the mammalia are confined is an un- 

 mistakable proof of this ; and the fact that birds are 

 at least by no means so strongly smelling convinces 

 us of the absence of glands in the skins of those animals. 

 The same may be said of reptiles and amphibia, broadly 

 considered for here as elsewhere there are exceptions. 

 There are for example musky smelling glands among 



10 



