54 DARWINISM AND THE PROBLEMS OF LIFE 



for instance, the wolf has become so cautious that 

 he often escapes from the most careful traps. The 

 endless attacks upon this dreaded robber have left only 

 particularly cunning specimens in existence. 



As a general rule the day's work of our mammals is 

 very monotonous. Brehm has compared it, in his 

 striking way, with that of the birds. The mammals 

 are, he says, not such light-livers as the birds. They 

 have not the liveliness and the unquenchable joyousness 

 of the lovers of the light ; though they have a certain 

 comfort and enjoyment of life. Except in their early 

 youth they refrain from useless exercise of their bodily 

 strength. For the bird, on the contrary, to live is to 

 move and to move is to live. The bird is never at rest, 

 and would like to turn the whole night into day. Its 

 little heart beats more quickly, its limbs are more 

 elastic, more wiry, than is the case with the mammals. 

 The mammal seems only to experience real joy in life 

 when it has packed itself away as comfortably as 

 possible, to sleep, or at least to doze. The bird is a 

 thing of movement ; the mammal, of sensation. 



This is quite borne out by their organisation. 

 The mammal, even when it can attain great speed, is 

 tied to the ground, and cannot move anything like so 

 independently as the earth-free bird, which can easily 

 outstrip our swiftest expresses. So it is with most of 

 the arts of movement. What mammal can vie with 

 the nut-hatch in climbing, as it runs, head downwards, 

 up the trunk ? Nor are birds backward sometimes at 

 swimming and diving. 



But now for the other side of the matter. How 



