654 
Mr. R. Shelford on the Pterylosis of the 
XLI.— On the Pterylosis of the Embryos and Nestlings 
of Centropus sinensis. By R. Shelford, B.A. (Curator 
of the Sarawak Museum). 
(Plate XIII.) 
The most remarkable feature in the young of Centropus 
sinensis is the clothing of long, white, thread-like structures, 
most strongly developed and most densely disposed on the 
dorsal surface of the head and body (Plate XIII.). Dissec¬ 
tion and microscopical- examination show these threads to 
be enormous prolongations of the horny sheaths which 
envelop the developing feathers, a narrow lumen extends 
from the base to the tip of each, whilst the base of each 
lumen, again, is occupied by a feather-papilla, situated below 
the skin. In order to avoid unnecessary circumlocution 
and repetition, I shall term these thread-like structures 
trichoptiles. The skin in young nestlings and ripe embryos 
is black, except between the rami of the mandibles and on 
the belly ; the white trichoptiles stand out in striking con¬ 
trast to this dark background, and give the young bird a 
sufficiently remarkable appearance. 
The horny sheaths of all the definitive feathers are not pro¬ 
duced to form trichoptiles; whilst, on the other hand, certain 
areas occupied in the young nestling and embryo by tricho¬ 
ptiles are in later stages devoid of feathers. To describe the 
changes in shape and extent of the pterylse and apteria 
during the passage from the trichoptile-clad embryo to the 
adult is the purpose of the present paper. 
Thanks to the generosity of Mr. Charles Hose, who has 
furnished me with several gradational examples, the material 
at my disposal can be divided, roughly speaking, into three 
stages, though the divisions are not very well marked. 
A nearly ripe embryo with a total length of 92 mm. con¬ 
stitutes Stage 1 (Plate XIII. A) ; a young nestling with a 
total length of 112 mm. may be regarded as typical of 
Stage 2 (Plate XIII. B, and figs. 1 & 2, p. 655) ; and nestlings 
ranging from 125 mm. to 145 mm. fall into the third division, 
