1910.] PLUMAGE OF THE RED GROUSE. 1007 



tinctive change, to avoid noticing how closely it approximates 

 to the nesting-plumage of the hen, and yet to think and 

 to speak of this " autumn " plumage as an " Eclipse " plumage. 

 In every respect it closely resembles the breeding-plumage of the 

 hen, and the one prominent discrepancy is that 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 appeal's almost as though the pathological postponement of 

 the moult, which is, after all, nothing but a sign and a symptom 

 of disease, has gi'adually developed into a normal habit in the 

 life of the bird ; and one is led to think that this habitual dis- 

 ability 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 Api-il and 

 in May), may have caused the alteration in the season of the 

 moult, simply because the vis vitce 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 bx-eeds in the winter- 

 plumage, without any further acquisition of new feathers, and, 

 as has recently been pointed ovit by Mr. Ogilvie-(Trant, what 

 have been regarded as new " spring-feathers " on the neck by 

 Mr. Millais 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 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 and in so far as it 

 continues, pigmentation may be altered, and so may growth ; 

 but once allow, first that the circulation has ceased beyond the 

 enti'ance to the base of the shaft, and secondly that the feather, 

 although still attached to the epidermis, is cut off from the 

 circvilation in the deeper living layer of the skin, then the 

 feather is no more likely or able to change the pigment which is 

 responsible for its pattei'n or its colour (except by external means 

 such as bleaching by sunlight) than if the same feather had 

 been plucked out and kept entirely separate from the bird. 



Once the feather is full-gi'own and the circulation in it 

 stopped there is no reason to believe that any thing can alter 

 it save svnilight and water, and oil supplied as an external 

 luiguent from the oil-gland. That ap])earances are most deceptive 

 in this respect must be allowed. Feathers may be collected from 



