No. 1. —SYSTEMATIC RESULTS OF THE STUDY OF 
NORTH AMERICAN LAND MAMMALS TO THE 
CLOSE OF THE YEAR 1900. 
BY GERRIT S. 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, chiefiy through the ac¬ 
quirement of vastly more extensive series of specimens than have 
ever before been brought togetlier, 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.^ 
The present paper is intended to summarize tlie systematic results 
1 The number of North American land mammals known in 1885 was 3(i8. About 
1450 are now recognized. While it is certain that some of these will eventually 
prove to have been established on insuificient 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. 
