89 



likewise lives in the Mississippi and its tributaries, while its 

 next of kin 3 Psephurus gladius, occurs in the Yangtse Kiang 

 and Hoang Ho rivers in China. These also are ganoid fishes 

 and, like the true sturgeon and bony pike, are the only few 

 remaining members of a very ancient and formerly abundant 

 group of fresh-water fishes. The fact of their survival in 

 these two continental centres might tempt us to adduce these 

 instances in support of the theory stated above, that Asia 

 and North America were recently connected with one another 

 by land, whereas the migration of these fishes is an old story 

 dating back to some remote geological period when their ances- 

 tors no doubt spread from one continent to the other by means 

 of a land connection which probably lay further south. Their 

 geographical distribution has obviously nothing to do with 

 the subject under discussion, which concerns a geologically 

 recent event. The cat-fishes or horned-pouts (Ameiurus) 

 are possibly of a more recent origin. They swarm in every 

 quiet stream and pond, especially in the eastern States pf 

 America. A single species (Ameiurus cantonensis) is found 

 outside the American continent, viz., in China. Finally 

 I may mention that the " suckers " (Catostomus), which are 

 very numerous in the American streams, are confined to 

 North America, with the exception of one species (Catos,- 

 tomus rostratus), which inhabits eastern Siberia. The last 

 case certainly indicates a former land connection between 

 North America and Asia, and consequently a dispersal from 

 the former to the latter, at a geologically recent date. Still 

 in the present state of our knowledge we are unable to deter- 

 mine whether the passing across to Asia of these fishes coin 

 cided with that of the great mammals whose dispersals I 

 have endeavoured to elucidate. 



It is impossible to discuss the relationship of all the Asiatic 

 to the Alaskan groups of animals, but no matter what class or 

 order we examine with a view to testing this kinship, we 

 find among almost all of them some indications of it. Dr. 

 Horvath,* for instance, recently dwelt on the large number of 

 species of Hemiptera (a group including bugs and allied 

 insects) common to Europe and North America. He quoted no 



* Horvath, G., " Faunes heuiipt6rologiques," p. 7. 



