of the male and the skull of the male is 127 per cent heavier than that of the female. Intergradation with races whose ranges border on that of _richardsonii_ is complete. On the northern boundary of the range of _richardsonii_ along the western shore of Hudsons Bay for perhaps a hundred miles north of Eskimo Point, there are intergrades with _arctica_. As judged by their lesser size, individuals of this population are influenced by the _semplei_-stock. Otherwise, intergradation on the northern boundary, with _arctica_, is abrupt whereas intergradation at the south, between _richardsonii_ and _cicognanii_, is gradual. Intergradation is similarly gradual between _richardsonii_ on the one hand and _bangsi_ and _invicta_ on the other. By speaking of the intergradation as abrupt, it is intended, in this instance, to indicate that in a relatively narrow belt, between the geographic ranges of _arctica_ and _richardsonii_, ermines intermediate in color-pattern, shape of skull, and size, bridge the gap between the ermine of the tundra (_arctica_) and that in the forest belt (_richardsonii_). It may be added that the degree of difference between the two subspecies just mentioned is approximately twice as much as between _richardsonii_ and _cicognanii_. The intergradation between _cicognanii_ and _richardsonii_ is gradual. By gradual it is meant that the change from one kind to the other is achieved in a wider area where ermines from locality A do not differ appreciably from those taken at, say, locality B, 50 miles farther south, although ermines from A and those from a third locality, C, say, 130 miles south, clearly show differences indicative of geographic variation. _Specimens examined._--Total number, 1035, as follows. Arranged alphabetically by provinces and districts and from north to south in each province or district. Unless otherwise indicated, specimens are in the United States National Museum. =Alberta.= 15 mi. above Smith Landing, 2; Fort Smith, 2 (1[77]); Smith Landing, 2; LaButte, Fitzgerald, 1[77]; Egg Lake, 15 mi. NW Ft. Chippewyan, 4 (2[75]); Lobstick Island, near Ft. Chippewyan, 1; Athabasca Delta, 9 mi. above mouth of main branch, 1; Athabasca Delta, Long Creek, 1 mi. W of main branch, 2; Ft. Chippewyan, 1; Peace Point, 1[75]; 18 mi. below Peace Point, 1; Embarass River, 7 (4[75]); Athabasca River, 1[2]; Ft. McMurray, 1; Athabasca River, Middle Rapid, 2; 60 mi. above Grand Rapids, 1; Boiler Rapid, 1; Entrance, 3[2]; St. Albert, 2.