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1916] Chandler: Structure of Feathers 
Part I 
GENERAL MORPHOLOGY 
J. PLUMULES 
1. Unspecialized Plumules 
a) Occurrence and Distribution—As remarked above, from a 
general survey of the feathers of a large number of species of birds, 
it is evident that certain generalizations regarding feather structures 
may be made. It is the intention of this portion of the paper to 
describe the general characters of various kinds of feathers, and to 
discuss briefly the range of modifications exhibited by them and their 
several parts. 
Plumules are small downy feathers which are usually completely 
covered by the contour feathers in adult birds. Their distribution 
on the body differs a great deal in different kinds of birds. They 
may be (1) evenly distributed over the whole body, both in the ap- 
teria, and in the pterylae between the contour feathers; (2) sparsely 
or unevenly scattered over the whole body; (3) confined to 
the apteria; (4) confined to the pterylae (only in Tinamidae) ; or 
(5) absent entirely. The table on page 256 shows the nature of the 
distribution of plumules in the various groups of birds, the data 
being derived from Gadow (1891), Beddard (1898), and others. 
In looking over this table it seems evident that a uniform dis- 
tribution of plumules is to be considered a primitive condition, yet 
in all of the ratite birds, which have usually been considered the 
most primitive, they are absent entirely. It seems to me that this 
may be explained in one of two ways: either that the ratite birds 
have degenerated from a higher type and have lost their plumules 
concomitant with a simplification of their contour feathers from a 
pennaceous to a downy type, or that the ratite birds show a condition 
of plumage more primitive than any other birds, and that in the 
course of evolution the downy contour feathers of these birds devel- 
oped along two separate lines, one leading to the soft, fluffy, almost 
shaftless plumules in both pterylae and apteria, the other to the 
highly specialized contour feathers in the pterylae only. Further 
