of the month. The rump and back are now completely covered with new black-centred feathers carrying broad-barred buff and black bands, and a few have a whitish terminal spot, similar to that found in the female The head and neck, breast and throat, are now clothed in broad-barred buff and black feathers, quite distinct from the more chestnut and more finely black-marked plumage of the winter. It is impossible on seeing a series of the birds showing this distinctive change to avoid noticing how closely this autumn plumage of the cock approximates to the nesting plumage of the hen, and yet it is wrong to think and to speak of this "autumn" plumage as an "eclipse" plumage, for it has arrived in the cock just two months later than it is normally due in the hen — far too late to be a breeding plumage. It appears almost as though the pathological postponement of the moult, a postponement which is, after all, nothing but a sign and a symptom of disease, has gradually developed into a normal habit in the life of Possible
cause of
postponement. the bird, and one is led to think that this habitual disability in the cock Grouse, which results from Strongylosis during the nesting, courting, and breeding season (a disability which causes the death of about eight cocks to every hen in April and in May), may have caused the alteration in the season of the moult, simply because the vis vitœ of the cock bird, insufficient as we now know it to be at the close of winter for the ordinary calls of reproduction, would be still more disastrously insufficient if preceded by an early moult.
At the present time the cock undoubtedly breeds in the winter plumage, without any further acquisition of new feathers, and, as has recently been pointed out by Mr Ogilvie-Grant, what have been regarded by Mr Millais as new "spring feathers" on the neck are in fact the old autumn feathers, which on that part of the body do not become worn and faded.
That any feather of the Grouse, either in the cock or in the hen, was ever altered as to its pigment either in pattern, or in tone, or in Change in
pigment
improbable. any other character, when once it had completed growth and had been cut off from the circulation, is at present an assumption which is not well supported by the physiology of feather growth.
Metchnikoff's observation upon the migration of leucocytes into hair and their action in removing pigment cannot for one moment be adduced as conclusive proof that the same thing may happen in the case of a full-grown feather. While the circulation is active in the feather shaft, and for as long
