EIGHTH ANNUAL REPORT. 189 



species after another into this Altai deer, which is in turn almost 

 indistinguishable from our great American wapiti, how can we 

 escape the conclusion that the centre of radiation of the genus 

 Cervus was in Eurasia, and our wapiti so recent an immigrant 

 from the Old World that it has not had the time to evolve, under 

 the varied influences of its new habitat, well-marked species, 

 there being at most only two or three races of subspecific value. 



Turning to the fossil record we find that no member of this 

 genus has been found in America of an earlier age than the Mid- 

 dle Pleistocene. 



A similar line of reasoning applied in turn to each of the large 

 American animals, enables us to draw what appear to be accurate 

 conclusions not only as to their original home, but as to the rela- 

 tive duration of the type in America. 



Not all our animals, however, came from the Old World, al- 

 though the predominating types undoubtedly did. South Amer- 

 ica contributed a few types, and others, like the raccoon, peccary, 

 prong-horn and American deer, are either autochthonous, or else 

 have been here so long that their specialization has taken place 

 entirely on this continent. 



To take up the possible places of origin of our living mammals 

 in the inverse order of their importance, we find them to be: a 

 migration by a possible land bridge over the Atlantic; migration 

 from South America; development in North America, and last, 

 and by far the most important, migration from Eurasia by way 

 of Behring Sea. 



ATLANTIC BRIDGE. 



A mid-Atlantic land connection has been suggested, but has 

 little evidence in its favor, and can be practically disregarded, 

 and, while there is no doubt that continuous land connected 

 Greenland, Spitzbergen and Scandinavia in Pleistocene times, no 

 known element of our fauna was derived from this source. 



SOUTH AMERICA. 



South America was entirely separated from North America 

 until the Pliocene, but apparently since that period has been more 

 or less continuously united to North America. The southern 

 continent, during this long period of isolation, before the Plio- 

 cene, developed several groups of large and clumsy animals which 

 almost defy classification, but which stand close to the Ungulates, 



