234 MR. F. H. WELCH ON LEPUS AMERICANUS. [Apr. 8, 
What is the rationale of the process in virtue of which to the 
naked eye the colour of the hair is changed from black or tawny to 
white? Is it dependent on an abstraction of pigment, an alteration, 
or new deposition ? and must we regard it in the light of some general 
condition of the animal frame modifying the whole capillary pig- 
mentary secretion, or, on the other hand, interrogate the hair itself 
for the solution of the problem? The gradual character of the pro- 
cess, the immunity of some hairs from all change whatever, the irre- 
gularity of its course in involving different hairs in the same portion 
of the body, the all but invariable commencement of change m any 
other part of the shaft than that first to be influenced by altered 
secretions, the temporary localization of the process to some one part 
of the shaft, entirely limited to this or gradually implicating the rest, 
and the freedom from all change in colour in the under-fur, incline the 
balance of evidence to the latter opinion, and, moreover, indicate a 
capability of action of one portion of the shaft of the hair indepen- 
dently of any general change affecting the whole, and derived from 
the organism within. It would seem that the rapid development of 
new hairs, varying in no appreciable respect except colour from the 
pile, called forth by the increasing rigours of climate for the pro- 
tection of the animal frame, involves the autumnal outer fur in the 
same process, leading to an increased length and thickness in the 
shaft of the hair by the superposition of layers of the same colour- 
less cells entering into the structure of the new growth—perhaps 
combined also with an arrested production of pigmentary matter. 
Although, as a general rule, it may be stated that the hybernal 
change commences about the first week in October, and is finished the 
first week in December, thus occupying two months, yet departures 
from it are not at all uncommon, both as regards the comparison of 
one individual with another at the same period of time, and as regards 
the modifications consequent on yearly climatic variations. For ex- 
ample, a specimen shot in December 1866 was only beginning to turn 
white. On November 6th, 1867, a skin (before the first fall of snow) 
had a head piebald, feet white, back with a scattered white hair, no 
undergrowth. On November 18th (after the first fall), two Hares were 
shot in the same vicinity, one changing, the other not. On the 22nd, 
from a high ground, one was perfectly white on head and feet, and 
ov each side and around the tail deeply patched of the same colour ; 
the other showed only slight superficial changes, but on separating the 
fur the new growth was easily detected, } inch in length, hidden under 
the autumnal coat. Again, on the 21st one was in the same state as 
the preceding, while another from the same vicinity presented a dark 
streak along the centre of the back gradually fading into the white 
sides ; change elsewhere accomplished except on centre of forehead, 
On the 28th one was pure white. In the first week in December 
1868 one was complete in the change; another was still very brown 
along the spine. On the 11th December 1868 three were examined, 
—one, ears not whitened at all in front, feet very reddish, body 
changed ; another, feet changed, side of face mottled, centre of back 
not yet implicated; the third, complete except a patch on each side 
