468 Mr. J. Lewis Bonhote on Moult 



proved, since the white feathers are worn at their edges ; 

 these edges do not change colour, but there is a space of 

 about I of an inch left white, which is lost by abrasion. 

 On the back there is a fairly complete moult, and also under 

 the chin and throat, but the new growing feathers are white, 

 not black or })arti-col()ured, and then change to the black 

 summer dress. 



All this must be qualified by axioms i. and ii., and 

 although I have no notes to that effect, it would not surprise 

 me to find new black feathers growing on a bird. But I hope 

 I have shown that in some eases this takes place by change 

 of colour, and that therefore change of colour is a possible 

 phenomenon. As to the physiological process which goes 

 on, I am not in a position to write about it at present, but 

 should like to draw attention to a paper by M. V. Fatio*, 

 in which he shows that an oil is continually making its way 

 into tl)e feather from body ; and this is further confirmed 

 and proved by Mr. Chadbourue in the paper quoted above, 

 both these gentlemen stating that this flow is not due to any 

 active agent, but to osmosis, capillarity, or some similar 

 action. Most pigments are soluble in ether, alcohol, or 

 chloroform, thus proving them to be of an oily nature. 



Now, if it has been proved that oil can make its way up a 

 feather, and, further, that all true pigments (black, red, and 

 their combinations) are of an oily nature, it necessarily 

 follows that pigment can make its way up also. 



I make no claim to any discovery in this matter. M. Fatio 

 coloured an oil and caused it to make its way up into the 

 barbs and barbules of a feather, in order that he might prove 

 that substances of an oily nature could find a passage through 

 the feather, entirely disregarding the far more important 

 discovery that ///^rwen/ could do so. I may mention briefly 

 that his theory (and it is one that apparently holds good 

 for several birds) was that pigment was formed in various 

 places in the growing feather, and remained there until it 

 was diluted by the colourless oil which made its way from 

 the body of the bird. 



* Loc. si'jira cit. 



