ORGANIC EVOLUTION 55 



separated two continents — an Indo-Malayan con- 

 tinent to which belonged Borneo, Sumatra, Java, 

 and the Malay Peninsula; and an Austro- Malayan 

 continent, now represented by Australia, Celebes, 

 the Moluccas, New Guinea, Solomon's Islands, etc. 

 Wallace first announced this ancient boundary, 

 and it has been called * Wallace's line.' He was 

 led to infer its existence by the fact which he 

 observed as he travelled about from island to 

 island, that, while the faunas of these two regions 

 are as wholes very different from each other, the 

 faunas of the various land patches in each area 

 have a wonderful similarity. Australia is a verit- 

 able museum of old and obsolete forms of both 

 plants and animals. Its fauna and flora are made 

 up prevailingly of forms such as have on the other 

 continents long been superseded by more special- 

 ised species. No true mammals, excepting men 

 and a few rats, lived in Australia when English- 

 men first went there. The most powerful animals 

 were the comparatively helpless marsupials. The 

 explanation of these remarkable facts is probably 

 this : The Australian continent, which formerly 

 included New Guinea and other islands to the 

 north, has not been connected with the other land 

 masses for a very long period of time. The develop- 

 ment upon the other continents of the more 

 powerful mammals, especially of the ungulates 

 and the carnivora, resulted in the extermination 

 of the more helpless forms from most of the 

 earth's surface. But Australia, protected by its 

 isolation, has retained to this day its old-fashioned 



