256 CARNEGIE INSTITUTION 



time. Vague notions abound but there is little certainty. And if 

 our knowledge of the big and conspicuous animals is so defective, 

 what may be expected of the obscure and rare forms ? 



We have selected the above question as an illustration because it 

 has so direct a bearing upon the history of our own North American 

 fauna; for clearly, if such a continuous land bridge existed between 

 the Old and the New Worlds toward the early days of the glacial 

 period that reindeer and ermine and lemmings could pass from Amer- 

 ica to Europe, we are justified in inquiring into the question which 

 animals wandered from Europe into America by the same bridge. 



But while we do not deem it necessary to go into further detail, it 

 may be mentioned, as highly instructive in this connection, that not- 

 withstanding all that has been written as to the relationship of the 

 animals in the Scandinavian mountains and the Alps, and in spite of 

 all the theories based upon this fact, such as that of the gradual fol- 

 lowing up of the receding northern and southern glaciers by the 

 arctic inhabitants of the central European plains, no satisfactory 

 comparison in the modern sense of the animals most important in 

 this respect has ever been undertaken. It is a fact worth noting 

 that it is little more than a year since one of the present writers 

 distinguished between the Scandinavian and central European vary- 

 ing hares. This separation made here in America, from material 

 in American museums, emphasizes the need of the work here pro- 

 posed. 



8. Special problems in Eastern Asia. 



(a) Former land connection between Asia and America. — Turn- 

 ing now to the eastern or Pacific side of the Eurasian continent, we 

 find equally important problems in even less satisfactory condition. 

 As far as they have a bearing on North American problems, it may 

 be said that their importance to us is even greater than those we 

 have mentioned above. Whatever we may think of a land connection 

 in glacial times between America and the Old World by way of 

 Spitzbergen or Iceland, there is less doubt as to the connection by 

 way of Bering strait, and while it is doubtful whether America has 

 received any additions to its Pleistocene or Postpleistocene fauna or 

 flora by way of the former, there is scarcely any doubt that a 

 large influx came by way of the latter. While there is a general 

 feeling among biologists that such is the case, it is very difficult 

 to prove it in detail, as was clearly shown during a recent "sym- 

 posium" or discussion of the matter in the Washington Biological 



