112 PRESIDENTIAL ADDRESS SECTION D. 



some common element in all of the termitophile faunas of the 

 world. 



Such a common element is not clearly observable, and the 

 evidence obtained from the termitophiles strengthens the view 

 drawn from a study of the present geographical distribution of 

 the termites themselves, namely, that the continents became 

 separated soon after the .main termite genera had become 

 dififerentiated, and had passed down from the north into 

 America, Africa, and the Indo-Malay Region. These termites 

 produced numerous species along the tropical zone, and at the 

 same time a termitophije fauna arose, drawn from the surround- 

 ing free-living arthropod fauna. If such a separation had not 

 occurred soon after the main genera had become evolved, we 

 should expect a closer af^nity among the termitophiles than 

 actually occurs. Thus the origin of the chief termite genera 

 must be pushed backwards into such a period as when the 

 primates passed down from the north into America and Southern 

 Eurasia. The nature of the termite fauna of Australia, with 

 respect to its relative paucity in species and primitive character, 

 is in agreement with the fact that placental mammals are absent 

 from that region, and it indicates that Australia was cut of¥ from 

 Eurasia at a still earlier period, when marsupials and less 

 specialised termites were almost cosmopolitan in their distribu- 

 tion. 



