HOLMES] ABORIGTlSrAL AMEKTCAN ANTIQUITIES- — PART I 43 



It is not apparent that intercontinental transfer has been wholly 

 blocked at any time to migrating hordes or wandering grou})s, 

 for if not bridged by land the intervening space may have been 

 bridged by ice or may have been an easy ferry after seagoing craft 

 came into use. The (iiiestion, then, is one not of the availability of 

 the avenues of approach at one period or another but rather that of 

 the actual arrival of migrating groups at the gateway and of the 

 pressure necessary to push them one step farther from the place of 

 their nativity after the manner suggested in earlier paragraphs. The 

 arrival of the precursors of the race during glacial or preglacial 

 times would depend primarily on the extension of his habitat to the 

 shores of Bering Sea, and the improbability of this, as already 

 pointed out, must be a})parent to every one who gives serious con- 

 sideration to the subject. 



