126 PRIMITIVE ANIMALS 



as surprising as the kangaroo. The reason of this 

 great development of the Marsupials in Australia is 

 not far to seek. Australia, at any rate since the 

 beginning of Tertiary time and probably long prior to 

 that period, has been entirely cut off from the rest of 

 the world, so that no representatives of the higher 

 Mammals, save man, his dogs, and a few species of 

 rats, have been able to colonize it. The Australian 

 and Tasmanian natives themselves probably did not 

 reach Australia until very late in Tertiary time, and 

 they have never developed sufficiently to act as an 

 exterminating force on the wild animals. Hence on 

 the vast Australian Continent and the connected 

 islands of New Guinea and Tasmania, the Marsupial 

 fauna has enjoyed an asylum free from competition 

 with the more perfect types of Mammalian creation, 

 which were being evolved in the rest of the world and 

 were rapidly supplanting the Marsupials there with 

 which they came in contact. The manner in which 

 Australia first received its Marsupial fauna is a 

 matter of speculation, but there is much to be said 

 for the view that they reached that country at a time f 

 when it was connected with South America by arms 

 stretching up from the Antarctic Continent, at a period 

 previous to the development of any of the modern 

 Mammalian types. Secure in the isolated Australian 

 region, the Marsupials are now represented by types 

 adapted to live under every sort of condition ; the 



