232 MR. F. H. WELCH ON LEPUS AMERICANUS. (Apr. 8, 
reddish-brown ones with white tips: these latter are evidently un- 
altered or partially changed summer varieties; but the mass of the 
pile, trebly increased in number and at least half an ineh in length, 
is the produce of the hybernal growth superadded to the elongated 
and blanched autumnal coat. The under-fur has increased ;4, inch 
in length, but is unaltered in thickness or colour. A crop of white 
hair has sprung up on the inside of the ear, on the outside and on 
the face the hairs have increased in length, and the shaft is partially 
or wholly whitened from the tip downwards. In most specimens no 
new hybernal growth is perceptible in these localities, in some there 
is a slight addition, in a very few it is as complete as on the back. 
However, where no increase in number ensues, compensation is effected 
by an extra augmented growth in the existent fur. On the legs the 
change is limited to a lengthening and bleaching of the outer hair ; 
often this is limited to the tips of the shaft; and an occasional 
absence of change in spots leaves an irregular fawn-coloured mottling 
and streaking, especially on the front paws ; the hair on the treading 
surface is lengthened and dirty white. On the underparts there is 
no addition beyond an increase of length of the fur ; occasionally the 
whiskers and eyebrows remain black. Thus the winter hue would 
appear to be brought about by a change of colour in the pile of the 
autumnal coat combined with a new hybernal white crop, the latter 
undoubtedly playing no small part in the colouring process and in 
the thickening of the fur. ‘There is no indication of shedding. An 
increase in length ensues over the whole body. On the underparts 
the change is limited to this, but elsewhere it is associated with a 
bleaching of the pile, generally commencing at the tip of the hair 
and involving part or the whole of the shaft. On the feet, and gene- 
rally on the outside of the ears and face, no additional growth is 
perceptible ; but on the inside of the ears, and over the whole back 
and sides, a thick crop of white hair springs up as the winter ad 
vances, and, blending with the changed surface, materially increases 
the thickness of the fur, protects the animal against the clemency 
of winter, and assimilates it in colour to external nature. The pro- 
cess may be summed up as a combination of colour-change (except 
in the underparts) of the lengthened outer hairs of the autumnal 
coat, with an additional hybernal growth ; the former universal over 
the body, the latter limited to certain portions. 
The shaft of the hair of the new growth is invariably white, a cir- 
cumstance which renders it easily distinguished from the autumnal 
hair in process of change. Careful examination of a great number 
of these latter hairs will render it evident that, although the blanch- 
ing process commences, perhaps, most frequently at the tip and 
proceeds downwards, involving the whole or a part only of the shaft, 
yet it is easy to obtain specimens (especially among the shorter 
variety of the pile) demonstrating its commencement at the centre, 
and occasionally at the attached extremity. The whiskers, which 
apparently do not lengthen but merely alter in colour, will demon- 
strate each variety. 
Microscopically examined, the hair of this Rodent, circular in 
outline, is composed of oval or irregular shaped cells placed end to 
