1916] Chandler: Structure of Feathers 261 
young and adult, as well as of the back and breast of a cassowary, 
failed to show any filoplumes whatever. What Nitzsch very probably 
mistook for filoplumes are the tips of feathers just growing out, which 
give exactly the appearance described by him for filoplumes. 
When present these anomalous feathers are always associated 
with contour feathers, though not always accompanying all feathers 
of this type; in Circus hudsonius, for instance, they could be found 
only in the dorsal, lumbar, and caudal tracts. When present they 
grow out in groups from the dorsal side of the socket of the contour 
feather with which they are associated. There may be only one or 
two of these in a group, or as many as ten in some water birds, ac- 
cording to Nitzsch (1867). In Circus hudsonius there are from five 
to eight in a bundle, no two in a bundle usually being of the same 
length. 
2. Structure 
As shown by Pyeraft (1909), filoplumes are really degenerate 
feathers, only the barbs of the extreme tip of the feather becoming 
attached to the slender shaft. The other barbs are formed more or 
less perfectly, but through a defect in development never become 
attached to the shaft. Nitzsch reports a case in which some downy 
barbs and barbules were found near the base of the filoplumes in a 
specimen of ‘‘Gallus bankwa domestica.’’ It is very probable that 
this was an abnormal case in which the development was not arrested 
as usual, or it may have been a filoplume which had not completed 
its development, and had not yet lost its deciduous barbs. 
Unlike either plumules or contour feathers, filoplumes never have 
the quill divided into calamus and shaft, the base not becoming hollow 
and pithy, and the superior umbilicus being absent. The only differ- 
entiation at the base of a filoplume is a slight widening and flattening 
(see Chandler, 1914, pl. 16 fig. 2). 
As a rule, full-grown filoplumes have exceedingly slender shafts, 
often ridged and pitted to give a silvery appearance like a fiber 
of silk, and they are naked except at the extreme tip, where a few 
rudimentary barbules are borne directly on the shaft, or on two 
or three rami which may be given off. In some species they are 
pigmented, e. g., in the robin, Planesticus migratorius, while in closely 
allied species, e. g., the bluebird, Sialia mexicana occidentalis, they 
have the typical, unpigmented, silvery color. 
