[ 347 ] 



IX. Ecdyms, as Morplwlogical Evidence of the Original Tetradactyle Feathering of 

 the Bird's Fore-limb, based especially on the Peretmial Moult in Gymnorhina 

 tibicen. By Edward Degen, F.Z.S. 



Eeceived October 16, 1901 ; read February 4, 1902. 



[Plates XXXVI.-XXXVIII.] 



Contents. 



Page 



I. Introductory 347 



II. Historical 348 



III. Method of Eesearch 351 



IV. Explanatory Eemarks on the Diagrams on Plates, Tables, and Charts 354 



V. Definition of "Moult" 355 



A. On " Adventitious Plumage " 355 



B. On the "Feathering of the Fledgling " 363 



C. On " Perennial Feathering " 365 



VI. " Orders of the Moult " in Gymnorhina tibicen 367 



A. Flight-feathers or Peunae alares = Remiges primores plus Eemiges cubitalea 



(Sundevall) 367 



B. Remarks on the Period of Growth and the Development of the Remiges 371 



C. The Bastard "Wing. Alula or Ala spuria = PlumsB poUices 371 



D. Extract from and Eemarks on the Table of Percentages for the Deficiency 



in the Power of Flight 375 



E. The Wing-coverts or Tectrices 376 



VII. Summary of the Order in the Perennial Moult of the Wing-feathers 390 



VIII. The Contour Feather-tracts or Pterylae 395 



IX. Conclusions 400 



X. Bibliography 410 



XI. Explanation of the Plates 412 



I . — Introductoky . 



J?HE main object of this paper is to give additional evidence in support of the 

 theory of the derivation of the feathering of the bird's wing. 



When I was engaged on the subject of Diastataxy (Aquinto-cubitalism), the peculiar 

 conditions of the flight-feathers during the moult seemed to indicate that, by a fuller 

 study of the perennial moult, the facts concerning the observations of the feathers of 

 the bird's wing might be considerably elucidated. 



In order, then, to form a solid foundation for the purely morphogenetic development 

 of the feathers, it was necessary to ascertain the mode by Avhich the perennial moult 

 of the individuals of a species of bird is made up, from the earliest to the last stages 

 of renewal; and, further, to what extent each feather participates in this annual 



VOL. XVI.— PART VIII. No. I.— May, 1903. 3 d 



