No. 1. SYSTEMATIC RESULTS OF THE STUDY OF 



NORTH AMERICAN LAND MAMMALS TO THE 



CIOSE OF THE YEAR 1900. 



BY GERRIT S.f MILLER, JR., AND JAMES A. G. REHN. 



THREE distinct phases or periods may be distinguished in the 

 recent history of the study of North American mammals. The first 

 was characterized by scanty material for investigation, and by the 

 prevalence of the conception of fixity of species. Under these con- 

 ditions it was inevitable that variation should have been ignored or 

 at least thoroughly misunderstood, and that a large number of 

 species should have been described. The close of this period may 

 be placed at about the years 1860 to 1865. The next phase came as 

 the result of the accumulation of more extensive though still in- 

 adequate material and the abandonment of the idea of fixity of 

 species. It was naturally a period of sweeping reductions. Va- 

 riation had been discovered and was henceforth to be the chief 

 object of study ; but its extent and limits were still vaguely out- 

 lined, and the important distinctions between the different kinds of 

 variation had not been made. This period continued until the 

 year 1889. The existing phase is the direct outgrowth of the last, 

 and represents no new conceptions or tendencies such as distin- 

 guished the latter from its predecessor. But, chiefly through the ac- 

 quirement of vastly more extensive series of specimens than have 

 ever before been brought together, the distinction between geo- 

 graphic variation and individual variation has been made. This 

 is the essential characteristic of the period. The effects of this 

 distinction are more far-reaching than might at first be expected, for 

 instead of continued reduction in the recognized number of North 

 American mammals, it has brought an almost bewildering in- 

 crease. 1 



The present paper is intended to summarize the systematic results 



1 The number of North American land mammals known in 1885 was 303. About 

 1450 are now recognized. While it is certain that some "of these will e\entnally 

 prove to have been established on insufficient characters, there can be no doubt 

 that the number to be eliminated is an insignificant fraction of the whole, a quantity 

 that may be ignored in view of the equally certain further increase that will take 

 place before the fauna of North America is completely known. 



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