152 Natural History of the 



have the power of flight, there are still forty-eight species of 

 mammals common to the Malay Peninsula and the thi*ee large 

 islands. Among these ai-e seven Quadrumana (apes, monk- 

 eys, and lemm's), animals who pass their whole existence in 

 forests, who never swim, and who would be quite unable to 

 traverse a single mile of sea ; nineteen Carnivora, some of 

 which no doubt might cross by swimming, but we can not 

 suppose so large a number to have passed in this way across 

 a strait which, except at one point, is from thirty to fifty 

 miles wide ; and five hoofed animals, including the tapir, two 

 species of rhinoceros, and an elephant. Besides these there 

 are thirteen Rodents and four Insectivora, including a shrew- 

 mouse and six squirrels, whose unaided passage over twenty 

 miles of sea is even more inconceivable than that of the 

 larger animals. 



But when we come to the cases of the same species inhab- 

 iting two of the more widely separated islands, the difficulty 

 is much increased. Borneo is distant nearly 150 miles from 

 Biliton, which is about fifty miles from Banca, and this fifteen 

 from Sumatra, yet there are no less than thirty-six species of 

 mammals common to Borneo and Sumatra. Java again is 

 more than 250 miles from Borneo, yet these two islands have 

 twenty-two sjaecies in common, including monkeys, lemurs, 

 wild oxen, squirrels, and shrews. These facts seem to render 

 it absolutely certain that there has been at some former peri- 

 od a connection between all these islands and the main-land, 

 and the fact that most of the animals common to two or more 

 of them show little or no variation, but are often absolutely 

 identical, indicates that the separation must have been recent 

 in a geological sense ; that is, not earlier than the Newer 

 Pliocene epoch, at which time land animals began to assimi- 

 late closely with those now existing. 



Even the bats furnish an additional argument, if one were 

 needed, to show that the islands could not have been peopled 

 from each other and from the continent without some former 

 connection. For if such had been the mode of stocking them 

 with animals, it is quite certain that creatures which can fly 

 long distances would be the first to spread from island to isl- 

 and, and thus produce an almost perfect uniformity of species 

 over the whole region. But no such uniformity exists, and 



