A ef: L/ 
Fic. 455a.—Feather. sh, shaft; v, vanes; A, barbule, with (bc) the barbicels, 
Fal (SM 
GS 
rs 
FO \ 
EM FalSUY - 
SRG i 
Fig. 455b.—Six stages in the development of the feather. Feathers arise in 
as of the dermis lined by the epidermis; at the bottom of the pit is a papilla 
A, Pap) the epidermal investment of which gives rise by rapid growth to the 
feather. FK in B is the germ of the feather; C, section showing the horny layer. 
At D, the barbs have grown out and become free; at EH, the barbules of the 
down-feather; F', the rudimentary feather; Cu, derma; SM, Malpighian layer; 
Sc, horny layer; SM}, Sc1. extensions of these ‘tissues into the feather-papilla, 
Pap; FK, feather-germ; F, F'), feather-follicle; P, pulp; Fal (SM}), folds of the 
Malpighian layer extending into the feather-germ, and enclosed externally by 
the horny layer HS(Sc1); both layers are seen in the transverse section (C); F'Sp, 
quill of feather. which breaks up above into a tuft of rays or barbs (HS?t); sec, 
sec, secondary rays (barbules) arising from the latter; R, rachis; V, vexillum.-— 
From Wiedersheim, mainly after Studer. 
[To face p. 523.} 
