166 THE GEOGRAPHICAL DISTRIBUTION 



them, either migrate to other countries, or pass the winter 

 in a state of torpor, from which they awake in spring. 

 This is especially the case with the birds, which are all 

 migratory in their habits. The most beautiful species come 

 to us from the sunny south, and disappear on the approach 

 of winter. 



In proportion as we approach the polar regions, the 

 trees become stunted and dwarfed in their growth, the 

 number of genera and species is still further diminished, 

 the oak, the walnut, the chestnut, and the hickory, are 

 replaced by dark and sombre forests of coniferous plants, 

 amongst which pines and firs are the most prominent. 

 Finally, these plants gradually disappear, and the last 

 lingering remnants of vegetable life are seen in the form of 

 mosses, lichens, and other cryptogamous plants, the exces- 

 sive rigors of the climate preventing any higher indications 

 of vegetable life. 



The animals in the arctic regions are few in number, 

 and their tints as dusky as the northern heavens. There 

 is not a single bird with brilliant plumage, and not a fish 

 with various hues. The artic regions form a district com- 

 mon to Europe, Asia, and America. On this account the 

 animals inhabiting them are sometimes identical ; in fact, 

 there is no genus of quadrupeds in the Arctic regions 

 which is not common to the three continents. The most 

 conspicuous animals are, the reindeer, the white bear, the 

 polar hare, the white fox, lemming, and' various seals. 

 There are immense flocks of predaceous and aquatic birds, 

 gulls, cormorants, ducks and geese, all belonging to the 

 lowest orders. Reptiles are altogether wanting. The articu- 

 lataare represented by numerous marine worms and minute 

 crustaceans. Insects are rare and of inferior types. Mol- 

 lusca are sparsely scattered m the adjacent seas along with 



