146 
JOURNAL OF MAMMALOGY 
that is acceptable to the gopher, indicate that these rodents can be 
successfully poisoned. While pelts of beavers and muskrats are of 
considerable value, gopher pelts are worth nothing, and in the Imperial 
Valley these animals appear to be of no use whatever. 
The rodent problems in the Imperial Valley are distinct from those 
that present themselves elsewhere in the state. Gopher control will 
be a hard fight in this section, growing harder and more expensive the 
longer it is put off. Any successful method of control must accord 
with the habits and food preference of this species, which at the present 
time are not well understood. A thorough study of the life history 
of this species should be made. The facts thus obtained, combined 
with actual field experiments in poisoning these rodents, would save 
thousands of dollars that are now being wasted in well meaning but 
ill-advised, unorganized, and wasteful attempts at control. 
Berkeley, California, 
A BROWN MUTATION IN THE OPOSSUM (DIDELPHIS VIR- 
GINIANA) WITH REMARKS UPON THE GRAY AND 
THE BLACK PHASES IN THIS SPECIES^ 
By Carl Hartman 
Through the courtesy of the United States Biological Survey and 
the United States National Museum I have been enabled to examine 
three brown specimens of opossums which clearly belong to the species 
Didelphis virginiana. The color of these is strikingly like the cinnamon 
colored mutant of the roof rat (Rattus ahxandrinus) described by 
Patterson (1920) who thinks that this form may be analogous to the 
cinnamon mutation of the guinea pig described by Castle and Wright 
(1916). Like the cinnamon rat the brown opossums appeared in the 
wild; and since the opossum belongs to the order Marsupialia this 
report is not without genetic interest. 
Before entering upon a detailed description of the new specimens it 
is necessary to recall the normal coat color of the opossum. Two phases, 
gray and black, have been described for the large North American 
opossums. In Z), marsupialis texensis both phases are mentioned by 
1 Contribution No. 153, Zoological Laboratory, The University of Texas. 
