THE DISTRIBUTION OF ANIMALS. 361 
co, and West Indies; the Neoarctic, including the rest of 
America; the Palearctic, composed of the eastern conti- 
nent north of the Tropic of Cancer; the Africano-Indian, 
or Africa south of Sahara, Southern Asia, and the western 
half of the Malay Archipelago; and the Australian, or the 
eastern half of the Malay Islands and Australia. 
Life in the polar regions is characterized by great uni- 
formity, the species being few in number, though the 
number of individuals is immense. The same animals in- 
habit the arctic portions of the three continents; while the 
antarctic ends of the continents, Australia, Cape of Good 
Hope, and Cape Horn exhibit strong contrasts. Those 
three continental peninsulas are, zoologically, separate 
worlds. In fact, the whole southern hemisphere is pecul- 
iar. Its fauna is antique. Australia possesses a strange 
mixture of the old and new. South America, with newer 
Mammals, has older Reptiles; while Africa has a rich 
vertebrate life, with a striking uniformity in its distribu- 
tion.” 
In the tropics, diversity is the law. Life is more varied 
and crowded than elsewhere, and attains its highest devel- 
opment. 
The New-world fauna is old-fashioned, and inferior in 
rank and size, compared with those of the eastern conti- 
nents. 
As a rule, the more isolated a region, the greater the 
variety. Oceanic islands have comparatively few species, 
but a large proportion of endemic or peculiar forms. Ba- 
trachians are generally absent, and there are no indige- 
nous terrestrial Mammals. The productions are related to 
those of the nearest continent. When an island, as Brit- 
ain, is separated from the main-land by a shallow channel, 
the mammalian life is the same on both sides. 
Protozoans, Ceelenterates, and Echinoderms are limited 
to the waters, and nearly all are marine. Sponges are 
