Class 5. Aves. 



433 



longest feathers on tlie body .; as a rule, they have no aftershafts, 

 and the down-like proximal portion is very small, or is absent; 

 they lie in very deep feather-follicles, the remiges in a row along 

 the outer edge of the fore-arm and hand, the rectrices on the tail. 



In tte extinct Archmopteryx, tlie rectrices were arranged in two longi- 

 tudinal rows, one on either side of the long tail. In some existing Birds 

 also, they occur in two distinct oblique rows on the much shoi-tened tail ; in 

 others, this part is so very short that 



the longitudinal series foi-m a cui-ved ^ B 



transverse row. 



The down feathers [flumce), 

 which are generally completely covered 

 by the contour feathers, differ from 

 them, in that the whole vexillum is 

 similar to the proximal portion in the 

 latter; they consist of soft barbs, 

 which are often very long and beset 

 with long barbules without hooks, the 

 shaft is thin and feeble, often even 

 quite rudimentary, so that the barbs 

 arise close together at the distal end 

 of the quill. There is often an 

 aftershaft on the down feathers ; 

 not infrequently it is almost as large 

 as the main shaft. The down feathers 

 are usually whitish or grey, whilst 

 the contour feathers vary much in 

 colour. The two types described 

 pass gradually into each other ; there 

 are plumse which, in virtue of their 

 strong shafts, etc., approach the 



pennse, and modified pennse which are so loose and soft, or which 

 possess so small a portion with hooks, that they form a transition to 

 the plumse. 



A special form of pluma is the so-called filoplume, a delicate feather 

 with long thin shaft, in which the barbs are few in number, and at the tip of 

 the shaft only ; they occur in almost all Birds, arising close to the contour 

 feathers. 



Among pecuUarly developed feathers, the following may be mentioned: 

 ospreys, which grow on certain parts of the head in many Birds and have 

 no barbs, or only a, few, at the base of the shaft ; the pennsB, in the R a t i t ae, 

 from which hooks are entirely absent, even from the stiff distal barbs, and which, 

 in the Cassowaries , and Emeus, are fiu-ther remarkable in that the main and 

 altershaf ts are equally weU developed ; the remiges of the Cassowary, in 

 which the long stiff shafts are entirely without barbs. 



Newly hatched Birds are, as is well known, usually covered, over larger or 

 smaller tracts, with down feathers, which generally consist only of a short 

 quiU and a tuft of barbs (Fig. 359 A) ; oocasionaUy (Ducks, Ostriches), besides 

 the quill, there is a thin shaft with bai-bs. These down-feathers are connected 



Fig. 360. Tail of : A ArchcBopteryx, 

 B Swan, G Hen, seen from above. 

 Diagrams to show the arrangement of 

 the rectrices. / apertures of feather 

 follicles, apertures of uropygial 

 glands (in B the latter are diagram- 

 matically indicated). — Orig. 



