FEATHERS 245 
is beset with two series of numerous radii, forming a fluffy plumage 
which is still more characteristic of the young in Accipitres, Pusseres, 
Psittaci, and Striges. 
(3) In Galline there are from 10 to 12 somewhat stiff radius- 
bearing rami, springing from a slender rhachis. 
(4) In Anseres a feeble rhachis bears all the biserially radiated 
rami, forming feathers which closely resemble the Downs of mature 
birds, and are devoid of an Aftershaft. 
The Neossoptiles differ much in the various groups of 
Ratite. In Struthio they attain a length of 10 cm., and consist of 
a calamus | cm. long, which may carry as many as 30 rami, each 
biserially beset with radii, and these again are furnished with cilia. 
The distal part of some of the rami is flattened and bears no radii. 
In the absence of any trace of rhachis these feathers agree with 
our second type. In Lthea the Neossoptiles measure 6 cm. in 
length and are composed of a feeble shaft carrying numerous rami 
with their radii—the tips of the former being split into two or 
three thickened ends. In Casuariws each primitive feather consists 
of a long and slender rhachis bearing two series of rami, and con- 
sequently resembling exactly one-half of the double Final feather. 
In Dromxus each Neossoptile, which may be 4 cm. long, has a 
short calamus carrying a long dorsal rhachis and a much shorter 
ventral Aftershaft—each of them furnished with from 5 to 9 rami 
measuring from 1 to 2 cm. in length, and these again beset with 
numerous radii without cilia. This is the only known instance of 
a Neossoptile with an appendage, and it is significant that the 
latter is smaller than the principal shaft, and only in its final stage 
equals the rhachis in size. 
If we consider the condition of the various types of Neosso- 
ptiles, above described, with reference to the presence or absence 
of an Aftershaft in the Teleoptiles, we are led to conclude that 
this appendage, and consequently 
also the double feathers of certain 
fatite, are secondarily acquired 
and not primitive features. 
The first indications of feathers 
appear about the fifth or sixth day 
of incubation as slight pimples on 
the still semi-transparent skin of  Loncrruprar Section oF AN EARLY 
the embryo. Each pimple is pro- é gee oe age th 
FE, Epitrichium; M, Malpighian cells ; 
duced by a cluster of dermal cells, P, Pulp; S.c. Stratum corneum; *, Place 
covered by a few layers of epi- where the Malpighian cells grow downward 
dermal cells, the outermost of ' frm the follicle. 
which forms a single layer of flattened cells, the epitrichiwm, while 
the rest, the stratum Malpighii proper, are cylindrical and soon 
increase to form several layers. All the cells of the whole 
