Five hundred wolf specimens were studied. They represent populations from Alaska to Keewatin and from Vancouver Island to Manitoba. Pelage color varies nearly from black to white. There are no discrete color phases. Pale wolves are more numerous and dark wolves less numerous toward the tundra (northeastward) between Great Slave Lake and Great Bear Lake. Judging from color variation, wolf populations intermingle by associating with caribou at migration. Male wolves are larger than females (approximately 4% in linear skull dimensions). Northeastern individuals have a shorter and relatively broader skull than southwestern ones. Multivariate divergence in twelve skull dimensions is approximately proportional to geographical separation. This may express genetic differentiation "by incomplete isolation. But the pronounced northeastward zonation of the environment may have direct influences upon growth processes. Interpretations in terms of genetic affinities are hypothetical and taxonomic conclusions are postponed. Simultaneous analysis of biometrical data appears indispensable to disclose major trends of geographic variation. / Science, Faculty of / Zoology, Department of / Graduate