1883.] 211 [Jeffries. 



the mucous cells are offered every facility for the absolution of 

 the nutrient fluids which saturate the pulp. Lastly, the cell 

 walls of the barbs and barbules become converted into a sort of 

 horn, and the protoplasmic contents dry up. 



The quill, which may be regarded as the last stage in the growth 

 of a feather, is formed from the mucous and adjacent transitional 

 cells at the base of the papilla, In this part the epiderm never 

 becomes folded or thickened as in the upper parts, but remains as a 

 simple sheath about the papilla. The deeper cells become con- 

 verted into long threads of horn and form a tube or cylinder 

 which, when the pulp dries, forms the quill. The epitrichial 

 and a varying number of transition cells dry up and remain in 

 place only by virtue of their position in the feather-pocket. 



The pulp slowly withers at the end as the tip of the feather 

 becomes complete and needs no more food ; so by the time of 

 hatching it is quite small. At this time the epitrichial and outer 

 horn-cells are shed, and the feather, by its elasticity spreads out 

 and slowly sets into the adult structure. 



So far nothing has been said of pigments, because they are 

 accessory to, and not an essential part of feathers. In cases 

 where a feather is destined to have a pigment the first traces 

 appear in the epiderm about the middle of incubation, — from 

 the twelfth to seventeenth days in chicks and ducklings. The 

 pigment simply appears to accumulate, granule after granule, 

 within the cells destined to form the feather-parts. Besides 

 these pigments a brownish pigment may sometimes be seen in 

 the epiderm of very young papillae. 



It would be difficult to say what becomes of this brown pig- 

 ment. It very probably disappears after the manner of the pig- 

 ment in the epiderm of the scutae. 



DEVELOPMENT OF PINFEATHERS. 



Although much has been published upon the development of 

 feathers nearly all the papers were written before the subject 

 was thoroughly understood. 



Thus Meckel (7), Cuvier (8), Reclam (12), Schrenk (11) and 

 Holland (12), regarded the feather as a secretion moulded in a case. 

 Their supposed case being the various parts of the pulp and outer 



