ME. E. DEGEN ON ECDTSIS. 363, 



main, and the other the same substance required in the building-up of the after- 

 shaft. In speaking of the latter, Holland, on p. 346, I.e., says: " Bei Federn mit 

 Afterschaft bildet sich dem ersten gabelformigen Streifen gegeniiber am Bauche des 

 folliculus noch ein zweiter ahnlicher Langsstreifen, an denen dieselbe Bildung vorgeht, 

 wie wir eben gezeigt, und Aex folliculus lagert nach seiner vorderen und hinteren Seite 

 Mark ab. Wo das corpus calmni heginnt verwachsen heicle Schdfte zu Spule" ^. 



Any doubts existing as to the structural plan of the primitive contour-feathers are 

 dispelled consequently by the retention in the Cassowary and the Emu of the original 

 feather-structure. This was a diijjlicated organ (see also Nitzsch, p. 9), of which the 

 two component parts — in the birds alluded to — are still of equal length and strength ^ 

 These latter qualities are carried out to such a point of perfection that it is really 

 difficult to determine which is the rhachis and which the hyporhachis^. 



For the reduction of the latter (to f the length of the main shaft in the Grouse), 

 to its total disappearance, we get every degree of perfection in the develop- 

 ment for the main shaft of the feather towards that highest of degrees, as attained 

 by the Oscines amongst the Passerine birds at the expense, as it were, of the 

 after-shaft. This more highly specialized and simple form of feather, as acquired in 

 recent types of birds for perfected adaptation to flight, is then really only one-half of 

 the feather, and, however incongruous the inference may be, is a degeneration from the 

 original duplex structure. 



B. On the " Feathering of the Fledgling." 



A probably common feature of all the Carinatse is the mode in which they acquire 

 the first set of flight-feathers. The supply of this first set of quills on the wing is 

 generally concurrent with the appearance of the greater portion of the contour- 

 feathers in the principal tracts of the trunk and on the head. 



In the Gymnopcedes the remiges appear somewhat in advance of the latter. They 

 also appear simultaneously with the upper major coverts by practically the whole 

 series shooting out along the posterior margin of the fore limb and in synchronism 

 (see text-figure 2, p. 364, of young Parrakeet). Indeed, the upper major coverts even 

 precede the remiges in some birds, judging from a statement made and figures given 

 by Pycraft (39) {cf. footnote, p. 251, & pi. xvi. fig. 1, I.e.) in the case of the young 

 of the Common Fowl and that of a Pigeon. This I can also confirm from my own 



1 The italics are mine. 



' In feathers of equal lengths for the two parts, such as in the Emu, it can be reliably ascertained only 

 when ire situ. As a symmetrical structure consisting of two equivalent parts, it naturally follows that their 

 ventral or, more correctly designated, inner sides face each other, whilst the outer sides (dorsal for the main, 

 ventral for the accessory feather) are averted, irrespective of the convexity of their surfaces, which is a 

 concentric one for both. 



VOL. XVI. — PART VIII. No. 3. — Hay, 1903. 3 f 



