1883.] 237 [Jeffries. 



We now come to the feathers. These have often been com- 

 pared in various ways to hairs, and many feathers have been 

 described by the older writers as hairs. No hairs, however, exist 

 among birds ; all the plumage is composed of feathers and devel- 

 oped on the same plan. 



The modern view of feathers and hairs is that they are allied 

 structures, yet Gegenbauer, in his Comparative Anatomy, speaks 

 of them as divergent structures. The supposed genetic relations 

 of hairs and feathers were based on the supposed identity of the 

 early forms. It is now known, however, that their early stages 

 are the exact reverse of each other. A hair is formed in a solid 

 ingrowth of the epiderm, while a feather is formed from the 

 epiderm of a large papilla of the skin. Again a hair does not 

 contain any of the mucous cells, while a considerable part of a 

 feather consists of them. Yet again, a hair never conflicts with 

 the almost universal law, that the mucous layer shall retain its 

 vitality, and its under surface remain in contiguity with the cutis 

 vera ; a feather does, — the under side of a feather being the 

 inner side of the epiderm. 



The resemblance between hairs and feathers consists only in 

 their being both horny structures of the epiderm, with their bases 

 in sacks, while their differences are many. We must, therefore, 

 consider feathers and hairs as distinct structures. 



Certain authors have stated that feathers and scales were 

 homologous, thus completing the magic circle. The basis for 

 comparison being that both originated as papillae and the sup- 

 posed scale-like nature of the remiges of penguins. But scuta (I 

 know not about scales) do not originate as papillae, but folds, 

 and remain so during life. At no period of life is there the faint- 

 est resemblance in form. Again, Studer has shown that the 

 imagined scale-like nature of penguin feathers is an absolute fal- 

 lacy. Finally, all the peculiarities of the mucous layer separates 

 the feather from the scale. 



It hardly seems necessary to return to the papillae of the mouth. 

 When treating of these appendages I endeavored to show that 

 their resemblance consists in both being formed from papillae. 



Notwithstanding various statements to the contrary, the fact 

 that feathers grow upon scuta shows them to be distinct struc- 

 tures. From the first to the last scuta are folds, at no time 



