16 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
The red phase of Evotomys gapperi occurs throughout the Hud- 
sonian and Canadian zones in Ontario and penetrates the northern 
border of the Transition zone in such cool, damp localities as give it 
the necessary climatic conditions. In Ontario the brown phase has 
thus far been found on the north shore of Lake Superior only. 
The series that I collected during August, September, and October, 
1896, includes 29 skins (all in the red phase) from North Bay, and 
51 skins (46 in the red phase, 5 in the brown phase) from the north 
shore of Lake Superior. Mr. Brooks has sent me about a dozen 
specimens (all red) from Mount Forest. 
A study of all the available specimens of Evotomys gapperi from 
northern localities in eastern North America convinces me that the 
animal is dichromatic, and that it assumes independently of age, sex, 
or season a red pelage, E. gapperi , or a brown pelage, E. ‘ fusco- 
dorsalis .’ Throughout the southern part of the animal’s range the 
red phase dominates to the nearly complete exclusion of the brown. 
The brown phase becomes conspicuous in the lower edge of the 
Hudsonian zone (Trousers Lake, N. B., Lake Edward, Quebec, the 
north shore of Lake Superior), and at the northernmost point from 
which I have seen specimens (Hamilton Inlet, Labrador) it greatly 
outnumbers the red. 
The reasons for considering Evotomys ‘fuscodorsalts ’ the brown 
phase of E. gapperi instead of a distinct species as at first supposed 
may be briefly summarized as follows: (1) typical examples of the 
two ‘species’ differ in color only, and show perfect agreement in 
size, proportions, and in cranial and dental characters; (2) individuals 
representing each type of coloration live together in the same run¬ 
ways ; (3) a perfect series of intermediates connects the two 
extremes. 
These facts admit of only two interpretations, that Evotomys 
gapperi is a dichromatic species, the red phase of which ( gapperi ) 
occurs throughout the animal’s range, while the brown phase ( L fus¬ 
codor sails ’) is dominant at the north, but rare or absent at the south ; 
or that E. gapperi and E . 4 fuscodor sails ’ are distinct species which 
so far as known differ from each other in color onlv, which live 
together, have precisely similar habits, and hybridize freely. The 
first alternative is much the more reasonable, as it is in harmony 
with the facts already known in the case of some other dichromatic 
mammals. While typical specimens in red and brown pelage are 
very unlike in appearance, it is impossible to find any differences in 
