THE DISTRIBUTION OF ANIMALS. 373 
gonia; the Musk - rat, from the Arctic Ocean to Florida; 
the Ermine, from Behring’s Straits to the Himalayas; and 
the Hippopotamus, from the Nile and Niger to the Orange 
River . 191 
Frequently, species of the same genus, living side by 
side, are widely different, while there is a close resern-' 
blance between forms which are antipodes. The Mud-eel 
of South Carolina and Menobranchus of the Northern 
States have their relatives in Japan and Austria. The 
American Tapir has its mate in Sumatra; the Llama is 
related to the Camel, and the Opossum to the Kangaroo. 
The chief causes modifying distribution are tempera¬ 
ture, topography, ocean and wind currents, humidity and 
light. To these may be added the fact that animals are 
ever intruding on each other’s spheres of existence. High 
mountain-ranges, wide deserts, and cold currents in the 
ocean are impassable barriers to the migration of most 
species. Thus, river-fish on opposite sides of the Andes 
differ widely, and the cold Peruvian current prevents the 
growth of coral at the Galapagos Islands. So a broad 
river, like the Amazons, or a deep, narrow channel in the 
sea, is an effectual barrier to some tribes. Thus, Borneo 
belongs to the Indian region, while Celebes, though but a 
few miles distant, is Australian in its life. The faunse of 
North America, on the east coast, west coast, and the open 
plains between, are very different. 
Animals dwelling at high elevations resemble those of 
colder latitudes. The same species of Insects are found 
on Mount Washington, and in Labrador and Greenland. 
The range does not depend upon the powers of loco¬ 
motion. The Oyster extends from Halifax to Charles¬ 
ton, and the Snapping-turtle from Canada to the equa¬ 
tor ; while many Quadrupeds and Birds have narrow hab¬ 
itats. 
The distribution of any group is qualified by the nature 
