8 STRUCTURE AND CLASSIFICATION OF BIRDS 



' powder down feathers,' ' is found in many birds belonging 

 to quite different groups ; they are usually aggregated into 

 special patches. These are simply down feathers of which 

 the tops continually break down into a dusty matter. 

 These powder down patches have been asserted to be lumi- 

 nous in the heron, and to aid it in attracting its prey ; but 

 the assertion seems to be void of truth. 



The feathers of birds are, with a few exceptions, coloured 

 either by the deposition of pigments alone, or by optical 

 tints derived from the actual structure of the feathers shown 

 up against a basis of dark pigment. The colours of birds' 

 feathers have been chiefly investigated by Chuech, Kruken- 

 BEEG, and Gadow,^ to whose papers the reader is referred. 



The arrangement of the feathers upon the wing requires 

 a special description. They have been carefully studied by 

 the late Mr. Wbay,^ from whose paper both the informa-, 

 tion and some of the explanatory illustrations have been 

 drawn. In the wing of the wild duck there is, as in all 

 -birds, a fringe of stout quills known as the remiges. These 

 are attached to the fore-arm and to the hand. The border 

 of the ulna, to which they are fixed, constantly bears impres- 

 sions of the quills. Here the feathers stand out at right 

 angles to the bone ; in the hand they become more and 

 more inclined forwards until the last of the series lies parallel 

 with the bone (phalanx 2 of digit II.) which bears it. Of 

 these remiges it is usual to term those which are inserted 

 upon the ulna the secondaries, and those upon the hand 

 proper primaries. But the term cuhitals is gaining ground 

 as an expression for the secondaries of many writers. The 

 first of the remiges is much smaller than the others, and 

 has been called the remicle ; it nevertheless belongs to the 

 series of remiges. The rest of the feathers of the wing are 

 known as the coverts or tectrices. There are four series of 



' L. Stieda, ' tjber den Bau der Puderdunen der Bohrdrommel,' Arch. f. 

 Anat. u. Phys. 1870, p. 104. 



' Gadow, in Bronn's TMerreich ('Aves '), treats of the matter in considerable 

 detail. 



" ' On some Points in the Morphology of the Wing of Birds,' P. Z. S. 1887 

 p. 343. 



