'20 



THE ORIGIN OF FEATHEKS FEOM THE SCALES OF 



EEPTILES. 



BY 



J. E. DuEUDEN, M.Sc, Ph.D., F.Z.S., 



Pr(ifc>iSor of Zonlofjjj, Hltodcs University College, (jrahawstoivn. 



With Plates IV and V. 



Read July 11, 1922. 



One of the many problems still confronting zoologists is that 

 of the origin of feathers as a covering of birds and as a means 

 of flight. No structures at all resembling them are to be found 

 in any other group of animals to indicate the course along which 

 they have evolved. Since the days of Huxley, however, very 

 little doubt has remained that, in some way, they represent the 

 scales of reptiles. Professor Huxley first showed that in many 

 respects the scaly, cold-blooded reptile is closely related to the 

 feathered, hot-blooded bird, -and subsequent investigations have 

 but served to support the conclusion. From this the view 

 naturally followed that the feathers of birds, however different 

 the}^ may at first sight appear, have in some manner replaced 

 the scales of reptiles. 



It is well known that scales and feathers are much alike in 

 the early stages of their development, both being formed as 

 upgrowths of the epidermis followed by the nutritive dermis ; and 

 it has been generally assumed that, by some means, scales have, 

 in the course of evolution, become frayed out until they have 

 taken on the character of feathers. Very little real evidence in 

 sujjport of the theory has, however, been forthcoming, much 

 less of how the fraying-out first took place. One of the latest 

 contributions is that by Professor J. Cossar Ewart,'^ who contends 

 that, while feathers are closely associated with scales in their 

 origin, they are developed independently from the skin imder the 

 scales, and not by a splitting of the scales or from fragirients 

 of the scales. 



Since birds are held to have evolved from reptiles, it follows 

 that the ancestors of birds must have been entirely covered with 

 scales, as are all reptiles at the present day. This scaly covering 

 has largely disappeared and has been replaced by feathers in all 

 modern birds, but relics of the former generally persist on the 

 legs and toes. It would, therefore, be reasonable to expect that 

 these surviving scales might, in some instances, indicate how 



* Proc Zoological Soc, Lond., 1921. 



