A SQUIRREL'S NP:ST. 93 



power, we also find a large development of the sense of 

 smell, which may be regarded as to some extent com- 

 pensatory. But it must never be forgotten that the 

 cleverness of the dog has been greatly increased by long 

 hereditary intercourse with man, while the cleverness of 

 the elephant, the monkey, and the opossum is all native 

 and self-evolved. The squirrel's paws stand him in al- 

 most equally good stead. For though he has no opposa- 

 ble thumb, he can hold a nut or a fruit between them, 

 rolling it about or adjusting it meanwhile ; and his teeth 

 also serve as regular tools, which further enable him to 

 manipulate an object held in his paws almost as well as 

 any other animal except the apes and monkeys. It is 

 observable, too, that his tail belongs markedly to one of 

 the two types common among forestine tree-haunting 

 creatures. Those which crawl or hang among the 

 boughs have generally prehensile tails to aid them in 

 grasping the branches ; those which run and leap from 

 tree to tree have generally bushy tails to aid them in 

 balancing themselves, and to act as a sort of aerial rud- 

 der. In the flying squirrels and many other similar ex- 

 otic types the use of such tails as a parachute is supple- 

 mented by extensible folds of loose skin stretching 

 between the legs or the fingers. 



A group which shows so much variety of specialization 

 for its peculiar functions is likely to be an old one ; and 

 in fact the squirrels rank among our oldest surviving in- 

 digenous mammals. As a class, they date back as far 

 in geological time as the lower miocene ; and even our 

 English species must have inhabited this country, practi- 

 cally unchanged in appearance or habits, for many 

 thousands of years, except when driven temporarily 

 southward by stress of passing glacial periods. 



