534 CHORDATA 



existence in many feathers of a rudimentary featlier, tlie hyporachis, 

 or ajler-shaj't, aitadied to tlie scape below. 



In contour feathers the barbs are, to a great extent, united into a i>ane. 

 Thev lie close together and paraUel, right and leftof the shaft, each rejieating in 

 miniature the entire feather, the barb haWng branches or barhulcs, which, over- 

 lapping the barbules of adjacent barbs, give the vane its close texture. The 

 vane is held together by minute honks on the barliules of one barb interlocking 

 with those of the next. Doicn fcallicrs (pliinia) dilfer from contour feathers in 

 the absence of hooks and the loose arrangement of the barbs. Since feathers 

 consist of cornihed epithelium and these cells arc held firmly (only in pmcdcr 

 doivn is there a gradual loss), they, like the scaly coat of the snakes and lizards, 

 must be molted vearlv and replaced bv new. 



Young birds or embryos have only down feathers. Later the contour 

 feathers arise in regularly arranged fcalhcr Iraiis, or picrylic, fietween which are 

 apten'a in which no contour feathers appear (fig. 5S3). Since the contour 

 feathers overlap like shingles, tliev form a firm coat beneath which the down 

 and semiplumes form a warm coat. Besides these covering feathers (coverts, 

 or hrtnt-c;. fig. 584, D) there are the longer feathers of tlie wing, the rciiugrs. 

 and the tail feathers, or rcclriccs [S-). The larger remiges form tlie chief part 



Fig. 5S5. — Wing skeleton of storlc (from Gegenbaur). c, c', carpalia of llrst 

 row, /;, humerus; 111, hissed metacarjials ami carpals of second row; />-/>", phalanges of 

 first three fingers; r, radius; 11, ulna. 



of the ■v\'ing; they spring from the part of the limb corresponding to the hand 

 (carpus, metacarpus, phalanges) and are known as primaries {HS). while the 

 sccaiidaries (.is), arising from the forearm, are shorter. These are overlapped 

 at the base by the covcrls [D, D', D") and by the paraplcriuni (SF) springing 

 from the shoulder. .\ few feathers arising from the tirst finger remain distinct 

 from the remiges and form the alula (EF). In the water birds especially the 

 feathers are oiled by the secretion of a pair of glands at the base of the tail 

 above the coccyx. 



Since the feathers are not only for protection, hut give to most birds 

 the power of prolonged flight, they predicate a special mode of life, 

 under tlie inllueirce of which all of the otlier organs exist. The character 

 of the skeleton, the respiratory organs, and in part the sense orgaiis and 

 brain, are connected with the power of flight. 



As the feathers of the wings, lilce the fins, form what may be called a 

 paddle working as a whole, tlie skeleton of these limbs is simplified (fig. 

 585), first, by the reduction of the fingers, of which oidy three with a small 

 number of phalanges persist (J), p', p") ; second, by fusion of the corre- 



