No. 603] 



THE ROLE OF ISOLATION 



176 



amination and measurement. (1) The Samoa lot, as a 

 whole, were paler than the redwood lot; (2) the tails of 

 the former were shorter, and (3) the ears were longer. 



To consider first the coat color, the mean difference be- 

 tween the two series of skins is evident at a glance. Like- 

 wise, it is plain that the palest Samoa specimen is paler 

 than the palest Eureka (redwood) specimen, and that the 

 darkest among the former is paler than the darkest 

 among the latter. It must be admitted, however, that the 

 two series overlap rather broadly,^ the darker skins of 

 the Samoa stock being as dark as or darker than the paler 

 ones of the Eureka stock. 



An attempt to express the color of a mammal's pelage 

 in terms of any set of ''standard" colors is beset with 

 great difficulties. Instead of a uniformly tinted, plane 

 surface, we have to do with a mixture of variously colored 

 hairs, further diversified by minute shadows and reflec- 

 tions. I have, nevertheless, endeavored, in a rough way, 

 to "match" the colors of these two races with those of 

 Ridgeway^s ''Color Standards and Color Nomencla- 

 ture. ' In the Samoa race, the general tone of the lateral 

 regions of the body lies between the "tawny olive" and 

 "Saccardo's umber," that of the dorsal darker stripe 

 being not far from "sepia." In the Eureka mice, the 

 lateral regions range from "Saccardo's umber" to 

 "sepia," the dorsal stripe being of a depth somewhere 

 between "sepia" and black. These comparisons will at 

 least enable the reader to judge of the degree of differ- 

 ence between the two racs.® 



As regards the tail, it was plain without measurement 

 that the average length of this member was greater in the 



skini 



season may be disregarded. 

 12. Published by the author, 

 studies of Feromyscus I plan 



