494 



Of ^yallace's regions, the Neotropical, owing to its very large pro- 

 portion of endemic genera, is therefore the most independent and 

 best established, the Nearctic the least. In an examination of 8300 

 selected genera, Handlirsch finds that only about 4% have a discon- 

 tinuous distribution and would therefore constitute the chief basis for 

 the contentions of the bridge-builders. But it appears that the 

 generic relations between the Neotropical and Ethiopian regions, for 

 which von Ihering constructed his " Archhelenis " land-bridge, are 

 actually feebler than those between the Neotropical and Oriental, 

 or between the Nearctic and Oriental or between the Palearctic and 

 Australian! Furthermore, the Neotropical is really more closely 

 related to the Palearctic than to the African insect fauna. These 

 facts are clearly brought out in the following numbers of genera found 

 to be common to the different regions, after excluding the cosmopoli- 

 tan species: 



Palearctic and Nearctic 1225 



Nearctic and Neotropical 1159 



Palearctic and Oriental 1083 



Oriental and Australian 754 



Oriental and Ethiopian 701 



Palearctic and Ethiopian 687 



Palearctic and Neotropical 571 



Palearctic and Australian 472 



Nearctic and Oriental 306 



Neotropical and Oriental ' 259 



Ethiopian and Australian 327 



Neotropical and Australian 228 



Neotropical and Ethiopian 195 



Nearctic and Australian 197 



Nearctic and Ethiopian 159 



