FOREST, AND ITS FAUNA 43 



common British squirrel {S. vulgaris), widely distributed 

 in the more northerly parts of Asia, as is well known, 

 rarely descends to the ground, and has great powers of 

 leaping. It shows interesting colour variations, tend- 

 ing to be darker in colour in the colder parts of its 

 range in summer, and turning white in winter where 

 the climate is severe. It wiU eat almost any forest 

 product, and hibernates during winter. The final stage 

 in the mastery over the forest is represented by the 

 Qjing squirrels, which are furnished with a parachute 

 by means of which they can take long leaps from one 

 tree to another, and thus obviate the risks due to 

 a descent to terra firma. Though chiefly inhabitants of 

 the tropical forests of Asia, one species occurs in tem- 

 perate Asia and one in temperate North America. 



The beaver, which haunts the streams flowing through 

 wooded regions, was once widely distributed over the 

 cooler parts of the northern hemisphere. The American 

 species, if not identical with the Eurasiatic one, is at 

 least very nearly allied. Beavers feed upon bark and 

 twigs, and also upon the roots, &c., of such plants as 

 water-lilies. 



While the porcupine of the warmer parts of Asia 

 inhabits rocky country, the porcupine of Canada is 

 a purely arboreal animal in habits, though it does not 

 possess the same adaptations to this mode of life as 

 are exhibited by its southern allies, the tree-porcupines 

 of South America, Mexico, &c. The Canadian form 

 (Erethizon dcyrsatus) follows the taiga to its northern 

 limit, and also follows the western coniferous forest to 

 its southern limit. It spends the greater part of its 

 time in the trees, though the nest is usually made on the 

 ground among stones. The food consists of leaves, 

 bark, twigs, beech mast, and other nuts, and the 



