172 EDWARD B. POULTON. 
on further, and that it takes place at an earlier stage in the 
ontogeny of the hair; while the proliferation of the epidermis 
also commences much earlier than in the feather-forecast, and 
is more extensive and rapid. 
On the other hand, it is argued that if the hair is homologous 
with the feather, there should be a more or less close agree- 
ment in (a) the final structure of the two, (d) their mode of 
development, and (c) their arrangement on the body. It is 
unnecessary here to compare the structure of hair and feather 
in detail. In both there is a (1) root (embedded in the skin) 
embracing a vascular papilla, which is of much greater extent 
in a feather than in a hair; and (2) a projecting shaft of horny 
cells (which in the feather is flattened like a scale, but bears 
secondary processes upon it, while in the hair it is cylindrical 
or flattened). With regard to the arrangement of these struc- 
tures, nothing need, I think, be said here. But in dealing 
with the development we are at once met with the fact that 
two divergent accounts have been given with regard to the very 
first forecast of the hair. Some authors, amongst them Gotte 
(2), Reissner (1), Studer (4), Kerbert (8), describe the first 
trace of a hair as showing itself in the form of a projection of 
the corium into the epidermis, just as in the feather and scale. 
This is the view which is taken by all those who regard feathers 
and hairs as homologous (Claus, Wiederheim, Hertwig, and 
others). 
It may be well to refer to the observations of Davies (5) on 
this point, who finds the earliest forecast of a hair—or rather 
a spine, for he studied the matter in the hedgehog—marked 
out by a proliferation of “ intermediate cells,” and not by the 
deeper columnar cells. He carefully describes the mode of 
origin of feather and spine, and regards both of them as de- 
scendants from a common scale-like structure. He holds that 
the “scales”? covering the feet of birds are not homologous 
with Reptilian scales ; the former frequently carry feathers, just 
as the “scales” of Dasypus carry hairs, and he argues that if 
the reptilian scale is equivalent to a feather and to a hair, then 
two of these homologues cannot be superposed. These scales 
