402 PHYSICAL CONDITIONS IN GENESIS OF SPECIES. 



the Vaiiiei- days proved 8o elusive. With the conseqvient immense increase of 

 material, of much hetter quality and from innumerable localities, the point of 

 view in regard to species and subspecies has greatly changed, resulting in 

 changes of nomenclature. Aside from the technical names there is little in 

 the article that I should modify were it to he now rewritten. All that it con- 

 tains concerning geographic and climatic variation, and the intluence of physical 

 conditions in the genesis of species and subspecies, is still satisfactory. In the 

 present reprint, the only changes found really desirable consist in the correc- 

 tion of a few typographical errors, and modifications here and there of technical 

 names, to bring them more nearly in harmony with present nomenclature. 

 These changes are for the most made in footnotes or by words inserted in 

 l)rackets. 



J. A. Allen. • 

 Ameiucan Museum of Natural History, 



Tslew York City, Fehruanj 1, 1006. 



