352 
DARWINISM 
CHAP. 
remained almost completely isolated ; and, being free from the 
competition of higher forms, they have developed into the 
great variety of types we now behold there. These occupy the 
place, and have to some extent acquired the form and structure 
of distinct orders of the higher mammals—the rodents, the 
insectivora, and the carnivora,—while still preserving the 
essential characteristics and lowly organisation of the mar- 
supials. At a much later period—probably in late Tertiary 
times—the ancestors of the various species of rats and mice 
which now abound in Australia, and which, with the aerial bats, 
constitute its only forms of placental mammals, entered the 
country from some of the adjacent islands. For this purpose 
a land connection was not necessary, as these small creatures 
might easily be conveyed among the branches or in the crevices 
of trees uprooted by floods and carried down to the sea, and 
then floated to a shore many miles distant. That no actual land 
connection with, or very close approximation to, an Asiatic 
island has occurred in recent times, is sufficiently proved by 
the fact that no squirrel, pig, civet, or other widespread 
mammal of the Eastern hemisphere has been able to reach the 
Australian continent. 
The Distribution of Tapirs. 
These curious animals form one of the puzzles of geographi¬ 
cal distribution, being now confined to two very remote regions 
of the globe—the Malay Peninsula and adjacent islands of 
Sumatra and Borneo, inhabited by one species, and tropical 
America, where there are three or four species, ranging from 
Brazil to Ecuador and Guatemala. If we considered these 
living forms only, we should be obliged to speculate on 
enormous changes of land and sea in order that these tropical 
animals might have passed from one country to the other. But 
geological discoveries have rendered all such hypothetical 
changes unnecessary. During Miocene and Pliocene times 
tapirs abounded over the whole of Europe and Asia, their 
remains having been found in the tertiary deposits of France, 
India, Burmah, and China. In both North and South 
America fossil remains of tapirs occur only in caves and de¬ 
posits of Post-Pliocene age, showing that they are compara¬ 
tively recent immigrants into that continent. They perhaps 
