THE DISTRIBUTION OF ANIMALS 455 



The tapir and llama are found here, and the rodents are more 

 numerous than in any other country ; the chinchillas, cavies, and 

 their allies, the guinea pigs, may be mentioned as noteworthy 

 examples. The marmosets and the monkeys with prehensile 

 tails belong to South America and are absent in the West 

 Indies. There are no sheep, oxen, or antelopes, and no Insectiv- 

 ora in South America, while the true swine are absent h 

 both North and South America, although the peccaries are 

 present in both. 



Considering the distribution of the animal kingdom as a 

 whole, we note that some animals are essentially cosmopolitan, 

 they are represented in all the great geographical divisions of 

 the earth ; others, which we have just been considering, are re- 

 stricted in distribution to one or two of the great zoogeographical 

 regions. Many groups of animals had in the prehistoric past a 

 very different distribution from what they have to-day ; thus 

 in the Pleistocene the elephant ranged over the greater part 

 of the Holarctic region, while to-day it is found only in the 

 Ethiopian and Oriental regions. Many animals, even within 

 the historic period, have changed their habitat, though chiefly 

 through human agency. There is often great irregularity in 

 geographical distribution; thus, instead of finding the Dipnoi 

 confined to one country or with a cosmopolitan distribution, 

 we find one genus in Africa, one in South America, and one 

 in Australia; the tapirs afford another example, one species 

 living in the Oriental region, the rest in the Neotropical. 

 Countries having very similar geographical positions and cli- 

 matic conditions may have very different faunae ; we have 

 already noted the difference in this respect between north 

 and south Africa, although the two regions are equidistant 

 from the equator ; the same is true of India and northern 

 Australia. We note further that the absence of any group 

 of animals in a country does not necessarily imply that that 

 country is unfavorable to the growth and development of such 

 animals; thus rabbits, when introduced by man into New Zea- 

 land, found it so favorable an environment that they became 

 a veritable pest through their increase in numbers. The gypsy 

 moth and the English sparrow, introduced into North America, 

 have found that country so favorable to their development that 



