362 MR. E. DEGEN ON ECDTSIS. 



If it could be shown that the " )3riniary " value of feathers could be established by 

 Brehm's observation, we should become possessed of a good test for their serial value. 

 Having paid attention to this feature whenever a favourable opportunity presented 

 itself, in no case have I met with the sessile condition of these early plumes on the 

 flight-feathers, though they are present invariably on the main coverts, both dorsal 

 and ventral, according to my observation. 



If, so far, we are supplied with even this slight means of differentiation between the 

 remiges and the rest of the covert- and contour-feathers, then we should have ample 

 proof that the principle of specialization, at any rate for the flight-feathers, is carried 

 out perceptibly early in the life of the bird ; and this differentiation seems to be of 

 considerable genetic importance. Moreover, there is the well-known fact of the 

 unvarying absence of after-shafts in the case of both categories of flight-feathers. 



It should be pointed out that Brehm (7 & 8) in his article, besides mentioning this 

 mode of replacement for the first plumage, also instances, by again referring to the 

 genus Si/rniutn, this peculiar condition as taking place during the second annual moult. 

 A repetition of this kind of renewal then naturally leads to the assumption of a 

 primitive condition of the plumage, to which the soft and downy feathering of the 

 Owls certainly points. And if we were to apply the existing analogy to some of the 

 Hatitce, the theory as to their descent from a bird which once possessed the power 

 of flight (Gadow (21), p. 667, quoting Fiirbringer) is not the less tenable on account 

 of their body-plumage still retaining this primitive style of feather-production, seeing 

 that such a combination still exists for the Owls. 



I may mention here that owing to the yet more primitive conditions of the feathers 

 on the trunk in some of the RatiUe, the extreme tips of the after-shafts, which in the 

 Cassowary and the Emu attain a length equal to that of their main shahs, joinfly 

 supjwrt the new-grozvth feather ^ with the latter. 



Necessarily this throws a curious side-light upon the structure of the feather in the 

 Struthiones, as Beddard (3), p. 18, rightly suggests, under the heading " Pterylosis," 

 by concluding that " The feathers of those birds have been called intermediate between 

 contour-feathers and downs. It may he that they are primitive ^ and that the struthious 

 birds have arisen from some ancient type in which the modern bird's feather had hardly 

 heen evolved " ^. 



To a great extent, then, will this help to solve the true relationship of the after-shaft 

 to the main shaft {cf. also Nitzsch (37), pp. 8 & 9). The importance attaching to the 

 bifurcated follicle, as shown in the beautifully executed drawing of its desiccated cells, 

 known as the " soul" in the quill by Holland (29), on table i., figs, 'lb & ob, becomes 

 at once fully apparent. Their union occurs in the cavum calami within the " corptcs 

 calamus," of which the one branch deposits the substantia rhachidis externa for the 



^ The italics are mine. 



