1897.] Hair and Feathers. 771 
The dermal portion, hereafter to be known as the pulp, has 
undergone modifications best understood by reference to a 
transverse section (fig. 7). Itno longer has a smooth contour, 
but is produced in a radial manner in- 
to longitudinal ridges which nearly 
reach to the epitrichium. As a result 
of this the epidermal portion becomes 
divided into a corresponding number 
of rod-like structures, each of which 
becomes surrounded by a structureless 
ensheathing envelope produced by the 
basal layer of the epidermal cells. Se ee a oen 
The pulp now begins to retract to- ne meie” aee. 
wards the surface of the skin, leaving sheath - pu, pulp; r, ridges 
the whole outgrowth hollow, except for sok pulp. dividing ve 
phe A epidermis into a series o 
structureless partitions—the pith of the rod-like structures. 
quill—here and there, produced by 
the retracting epidermis. The parts remaining external to 
surface of the body gradually dry up and become cornified, 
and, the epitrichial sheath breaking away, the epidermal rods 
just mentioned separate at their free ends, so that the well- 
known down-feather results, the basal, undivided portion of 
the outgrowth forming the small quill. 
During this formation of the down-feather the follicle be- 
comes much deeper, so that at length it presents considerable 
superficial resemblance to the hair follicle, and into it the der- 
mal pulp retracts after the full formation of the down-feather 
is complete. 
According to Davies all contour feathers are preceded by 
down-feathers, and even those cases which seem to form ex- 
ceptions to this statement are found upon more accurate 
observation to accord with it. The statement may be put in 
another way: the germ of the definitive feather isa direct 
- derivative of the germ of the down-feather. Let us now follow 
the development of a symmetrical contour feather. 
With the retraction of the pulp (fig. 8) the follicle widens 
while the feather papilla enlarges so as to contain a much more 
considerable pulp, but in other respects it is closely similar to 
53 
