158 POLAR PROBLEMS 



though for all we know the possibly originally white color of the 

 ancestral species may have facilitated the adoption of semi-marine 

 and polar habits. It may be well in this connection to call attention 

 to the occurrence in British Columbia of a white form of the black 

 bear genus {Euarctos kermodei) which externally is astonishingly like 

 a polar bear, though this reference should not be taken as suggestion of 

 a direct relationship between them. 



The Arctic Not a Faunal Center of Distribution 



Evidently the present inhabitants of the polar area are the modified 

 descendants of ancestors living to the south of it, which have become 

 adapted in structure and habits to the rigorous conditions of the polar 

 climate. The polar region therefore cannot by any stretch of the term 

 be considered a center of origin of the fauna. But neither is it in any 

 sense a center of faunal distribution. It is unfortunately true that 

 the animals composing this fauna have not all been studied sufficiently 

 from this particular viewpoint. In some of the cases, however, we 

 already know enough to support the above statement. Let us examine 

 that of the collared lemmings (genus Dicrostonyx) for instance. Tak- 

 ing the latest revision of these strictly Arctic animals,^ we find them 

 arranged as follows: 



1 Dicrostonyx torquatus 



la. D. t. torquatus: Old World from eastern shore of White Sea; eastward 



limits unknown; New Siberian Islands, 

 lb. D. t. ungulatus: Novaya Zemlya. 



2 Dicrostonyx chionopaes: Nizhne Kolymsk, northeastern Siberia. 



3 Dicrostonyx rubricatus 



3a. D. r. rubricatus: Alaska Peninsula; lower and middle Yukon Valley; 



Seward Peninsula; Arctic coast of Alaska and of the Mackenzie 



District eastwards to Coronation Gulf. 

 3b. D. r. richardsoni: From the western shore of Hudson Bay westwards 



through Arctic America, meeting and intergrading with 3a in the 



neighborhood of Coronation Gulf. 

 3c. D. r. unalascensis: Island of Unalaska, Alaska. 



4 Dicrostonyx exsul: St. Lawrence Island, Bering Sea. 



5 Dicrostonyx groenlandicus: Maritime districts of northern and eastern Greenland; 



also Grant Land, Grinnell Land, Ellesmere Land, and Baffin Island. 



6 Dicrostonyx hudsonius: Barren Ground area of the Labrador Peninsula. 



In analyzing this table, we may at once eliminate from our present 

 consideration the forms D. hudsonius, D. exsul, and D. rubricatus un- 

 alascensis as of only local interest on account of their isolated ranges. 

 Dicrostonyx chionopaes may also be left out as it is known only from a 

 single specimen of somewhat obscure characteristics. With regard 

 to the remaining forms, Hinton, in 1926, has to confess that the material 



5 M. A. C. Hinton: Monograph of the Voles and Lemmings, Vol. i, British Museum, London, 

 1926. 



