J] 4 8 MR. E. DEGEN OX ECDYSIS. 



process durint;- the pci-i(jd of complete feathei--change. This has been methodically 

 treated and fully explained in the present paper. 



By a " feather-change " there can be meant one thing only, namely, the actual 

 renewal of all the feathers. 



Physical changes, arising from external agencies, such as colour-changes, or the 

 abrasion of the wing-coverts and contour-feathers of the body, with their attendant 

 effects upon the pattern of the plumage, do not enter into the scope of this work. 

 Neither do partial changes, such as spring-plumages and the various forms of nuptial 

 garbs, of a sexual nature ; nor do the phenomena of " Albinism " and " Melanism," 

 all these bein«- either of a secondary origin, or, as in the latter case, of an Eetiological 

 nature. 



II. — Historical. 



With regard to the literature, it may be well to review in a general way those 

 papers which deal with the morphological history of the feathers. For a more 

 cxliaustive account of the history of the " moult," I refer the reader to the excellent 

 article of Dr. Allen (i), who has considered previous authors chronologically, and at 

 the same time has himself contributed to the physiology of the subject. 



By far the most important addition to the subject of " moult " was that made by 

 Blyth (4) in 1837, who, amongst other observations relative to colour-changes, makes 

 remarks on the plumage of birds which are of great value. Among many excellent 

 attributes characterizing his work, is that of a comparatively far advanced pterylo- 

 graphic knowledge before the time of appearance of the classic treatise of Nitzsch's 

 ' Pterylography,' edited by Burmeister, and first published in 1840 (Translation, 37) 1. 



Blyth's work is replete with information, based principally on the " Mallard " and 

 the " Widgeon " ; but though he bestowed much care on the partial and perennial 

 moult of the primaries and the tail-feathers, he treated but scantily the wing-coverts. 

 To this author's paper I have made frequent reference in the course of my own 

 research. 



Schlegel's famous "Address" (40) gave a new impetus to the subject of ecdysis. I 

 shall have to allude more particularly in the course of my own work to the various 



' Yarrell's endeavour to adduce evidence in favour of his view, " that the feallier itsdf becomes altered'"' — 

 though, in the course of his arguments he admits " that it is cerlainly difficult to understand how this 

 is so constantly effected in the web of the feather, where no vascularity can he slwwn to exist", even when 

 the part is growing " (c/. Allen, I. c.),— is shared also by Blyth to a great extent. Burmeister's observations 

 and researches into the histological structure of the feather (see Nitzsch, I. c), and also Holland (29), should, 

 however, finally dispel any doubts still existing on the point of a revitalization of the feather. 



" These italics are mine. 



