632 PtLoi'. 3. cossAte, eSwart on I'liE 



aftershaft. In some metaptiles the rhachis of the shaft extends 

 to the tip of the feather, in others it ends in two slender barbs 

 some distance from the tip. Though at the outset in Grouse 

 both the shaft and the aftershaft of the true feather may consist 

 of several moi-e or less distinct bundles, sooner or later the outer 

 barbs give rise to the shaft, while the inner form an aftershaft. 

 When the destined number of barbs for the shaft and aftershaft 

 have been produced the splitting of the epidermic tube is 

 arrested, and steps are taken to form a calamus in which 

 "cones" make their appearance. Evidently in Grouse, as in 

 Penguins, the aftershaft is not a forward elongation of the 

 calamus. An interesting stage in the development of a 

 Ptarmigan true feather is given in PI. IX. fig. 33. 



It has been asserted once and again that " in the great 

 feathers which form the ' quill ' or ' flight ' feathers (remiges) 

 of the wing and the tail-quills (rectrices) the aftershaft is in- 

 variably wanting" *. Assuming that in the case of the wing- 

 quills the aftershaft is invariably absent, it might be argued, that 

 these all-important feathers diifered in their origin and history 

 from the other true feathers, that while the trunk feathers may 

 possibly have developed from a.n epidermic tube, the wing- and 

 tail-quills were formed by the splitting of elongated scales. 

 Attention has already been directed to the fact that in the Mallard 

 during the earlier stages in the development of the wing- and tail- 

 quills, there is a vestige of the distal portion of an aftershaft (text- 

 tigs. 5 & 7). That in wing- and' tail-quills there may also be a 

 vestige of the proximal portion of an aftershaft is made evident 

 by PI. IX. fig. 34, which represents the aftershaft of a wing-quill 

 from a full-grown Grouse. 



Fowls are not supposed to have the aftershaft as well developed 

 as Grouse, nevertheless, as PI. IX. fig. 35 shows, the aftershaft in 

 the silky breed may be as long as the shaft. In its development 

 the aftershaft in the silkj^ breed follows the same coui\se as in 

 Ptarmigan. 



In the Guillemot the aftershaft is, to start with, sometimes as 

 long as the shaft. A Guillemot feather from the side of the 

 trunk is represented in PL X. figs. 36 and 37. In this case the 

 protoptile consists of seventeen bai-bs. Of the seventeen barbs 

 nine end in the tip of the shaft of the true feather, four end in 

 barbs of the shaft which join the rhachis a considerable distance 

 from the tip, and four, which represent the protoptile aftershaft, 

 are connected with the aftershaft of the true feather (PI. X. 

 fig. 37). 



Evidently the history of the aftershaft in Grouse, Fowls, and 

 Guillemots affords no support to the view that the aftershaft is a 

 secondarily acquired appendage, and may be said to fully estab- 

 lish the view that a complete true feather like a plumula coiisists 

 of a calamus and two shafts. 



* Pycraft, ' A Historj- of Birds,' p. 9. 



