94 GENERAL ZOOLOGY 



The Arctic realm includes all the land in the northern 

 hemisphere as far south as the northern limit of trees and 

 (so far as the insects are concerned) the tops of high moun- 

 tains in the temperate zone. It has already been noted that 

 the White Mountain butterfly (p. 48) belongs to this fauna. 

 The Eurasian realm comprises all of Europe south of the 

 Arctic realm ; Asia, north of the Himalayas and south of 

 the Arctic realm ; and Africa, north of the Desert of Sahara. 

 United with this, by many authors, is the North American 

 realm, embracing North America south of the Arctic realm 

 and north of Mexico. In past time land connection was 

 more complete than at present, and considerable migration 

 has taken place from one continent to the other. The South 

 American realm comprises that portion of the continent north 

 of Patagonia, and includes the West Indies, Central America, 

 the greater part of Mexico, and a portion of the most south- 

 erly part of Florida. This region has contributed many species 

 to our own fauna. South of this realm is another temperate 

 region in Patagonia, which corresponds in position to the 

 North American realm, but owing to its comparatively small 

 size it is not usually ranked among the great regions of the 

 earth. Its fauna is mainly derived from the South American. 

 Still farther south is an Antarctic region of eternal snow and 

 ice ; but little is known of the life of this region, and it may 

 be omitted from the list of the great faunal divisions. The 

 African realm includes all Africa south of the Desert of 

 Sahara. With this is often united the Indian realm, compris- 

 ing the Asian continent south of the Himalayas, and the 

 East Indies as far as the Strait of Lombok. The testimony 

 of geology is strong that these two realms were once con- 

 nected, though the water is now very deep and wide between 

 them. Madagascar is by some naturalists included within the 

 Indo-African realm ; by others, considered a separate region. 

 The last of the great faunal divisions is the Australian realm, 



