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Show 234 MR. F. H.WELCH ON LEPUS AMKRICANUS. [Ap*. 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 pigmentary secretion, or, on the other hand, interrogate the hair itself for the solution of the problem ? The gradual character of the process, the immunity of some hairs from all change whatever, the irregularity of its course in involving different hairs in the same portion of the body, the all but invariable commencement of change in 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 independently 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 protection 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 colourless 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 example, 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 on 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, liiich 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 |
