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 



