214 ANIMAL COMPETITORS 
experiments quiet and their results a secret; 
but a recent investigation pursued by W. H.. 
Osgood of the Biological Survey has gathered 
many facts as to method, of which I shall avail 
myself liberally. 
Variability of the red fox. The common 
fox, as has been said, varies from red to black, 
and these extremes, with the gradations be- 
tween them, form four more or less distinct 
phases, respectively known as red, cross (or 
patch), silver, and black. 
In the red phase the animal is entirely rich 
fulvous, except restricted black markings on 
the feet and ears, a white area at the end of the 
tail, and certain white-tipped hairs on the back 
and rump. From this phase to the next the 
black increases in extent until, in the typical 
“‘eross’’? fox, the black predominates on the 
feet, legs and underparts, while fulvous over- 
lying black covers most of the head, shoulders 
and back. A gradual increase of the black and 
elimination of the fulvous, or its replacement 
by white, brings us to the next phase, the ‘‘sil- 
ver,’’ or ‘‘silver-gray,’’ in which no fulvous ap- 
pears, the entire pelage being dark at the base 
