MOUNTAIN ANTS OF NORTH AMERICA. 



495 



The study of such a circumscribed group as the Formicidae would be 

 even more unfavorable to the views of von Ihering and other bridge- 

 builders than the more comprehensive studies of Handlirsch, because 

 the relationships of the ants of South America to those of Africa or 

 Australia would be represented, as I have stated, only by genera of 

 cosmopolitan range or at any rate common to the Palearctic and 

 Oriental regions, from which they could have found their way to the 

 New World over the Behring Sea and North Atlantic land-bridges. 

 Handlirsch summarizes his views on the migrations of forms between 

 the different regions in the following simple diagram, in which S stands 

 for the Neotropical and Ae for the Ethiopian region: 



Matthew (1915) has reached very similar conclusions from a study 

 of the distribution of Vertebrates and particularly of the mammals. 

 He finds the same fallacies as Handlirsch in the work of the bridge- 

 builders and expresses them in the following paragraphs: 



" 1. The discontinuous distribution of modern species is again and 

 again taken as proof that the regions now inhabited must have been 

 connected across deep oceanic basins, without considering the possi- 

 bility that it is a remnant of a wider past distribution, or that it is 

 due to parallel evolution from a more primitive type of intermediate 

 distribution, now extinct. Yet so many instances are known where 

 the geological record has furnished proof that one or the other of these 

 explanations applies to cases of discontinuous distribution, that it 

 would seem that these ought to be the first solutions of the problem 

 to be considered, and that in view of the known imperfection of the 



