128 ANIMALS OF THE PAST 



their feathers have become a sort of cross be- 

 tween scales and hairs. Hair and fur belong 

 to mammals only, although these creatures 

 show much variety in their outer covering. 

 The thoroughly marine whales have discarded 

 furs and adopted a smooth and slippery skin,* 

 well adapted to movement through the water, 

 relying for warmth on a thick undershirt of 

 blubber. The earless seals that pass much of 

 their time on the ice have just enough hair 

 to keep them from absolute contact with it, 

 warmth again being provided for by blubber. 

 The fur seals, which for several months in the 

 year dwell largely on land, have a coat of fur 

 and hair, although warmth is mostly furnished, 

 or rather kept in, by fat. 



No reptile, therefore, would be covered with 



* The reader is ivarned that this is a mere Jigure of speech, 

 for, of course, the process of adaptation to surroundings is 

 passive, not active, although there is a most unfortunate ten- 

 dency among writers on evolution, and particularly on mimicry, 

 to speak of it as active. The writer believes that no animal 

 in the first stages of mimicr}^, consciously mimics or endeav- 

 ors to resemble another animal or any part of its surround- 

 ings, but a habit at first accidental may in time become 

 more or less conscious. 



