248 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 
uniform grizzle of gray, black, and luteous or fulvous, and below muddy-gray, 
rustier on the breast. It may be, indeed, that these differences are somewhat 
regular and seasonal, as well as the change to white; but as few of our speci- 
mens are marked for season, we cannot make this out. As, however, several 
of our richest-colored skins are spring and early summer ones, we judge that, 
with the disappearance in spring of the white winter-coat, the brightest, 
sharpest pelage is put on, the vividness of the rufous or mahogany attaining 
a maximum in the breeding-season, or rather a little afterward, in midsummer; 
and that subsequently the hues grow cooler and more intimately mixed, until 
at length in the fall the whitening becomes manifest. 
Winter—lIn perfect dress, the animal is pure white all over. In the fall, 
the whitening seems to begin underneath and on the sides, to progress then 
over the lower back; the heavy color of the upper back and breast being the 
last to yield. Several specimens are white, with a narrow dorsal area of color, 
that spreads forward over the upper back and shoulder, and underneath still 
tinges the breast; others are curiously white, with lateral rufous stripes that 
nearly meet on the rump and then curve round the sides to the chest; others 
are pure white, except a sharp spinal stripe of grayish-black ; some are white, 
uniformly tinged with pale rufous all over. But it would be idle to attempt 
an enumeration of all the intermediate stages; although, in the midst of appa- 
rently interminable changes, doubtless rules of very general applicability may 
be deduced from observation of a few hundred specimens accurately marked 
for season. 
The two middle fore claws attain their maximum of development in 
winter. In spring and early summer, these claws do not appear very difler- 
ent from those of Myodes, though averaging larger, more bulbous at base 
underneath, with the terminal portion slenderer, straighter, and sharper. This 
bulbous portion underneath grows out simultaneously with increase in length 
and amount of curvature of the main portion of the claw, until it equals or 
even exceeds the length of the latter, and is quite as stout, or even stouter, 
being somewhat broad and pad-like. At this period, it runs the whole length 
of the claw, from which it is separated by a groove along the sides, and by a 
notch at the end, both of varying depth. The claw then looks nearly like 
two claws, one underneath the other. The pad would then seem to gradually 
sever its connection with the main claw by progressive increase of the con- 
striction marked by the lateral groove and terminal notch, as well as by loos- 
