774 The American Naturalist. [September, 
supply to the parts of the feather. The cells of which it is com- 
posed are dead and dry so that it seems impossible that any 
change can take place in it. The whole 
question of change in color of the fully 
formed feather was recently reopened by 
Mr. J. A. Allen who maintained that, once 
formed, the feathers do not change in their 
markings. The whole history of develop- 
ment seems to afford him full support. 
Yet this year the attempt has been made 
to show that feathers do change in their 
12.—A section markings. In this, as the matter now 
n stands, the burden of proof is upon those 
anpeire seri tha feather who support the possibility of change. 
ing out of the barbs (b) Another aspect of the hair and feather 
eine the vane; s, question must now be taken up. How 
; did these two structures come into exist- 
ence? They certainly were not formed de novo, for it is one of 
the axioms—we had almost said—that all structures are to be 
traced back as modifications of pre-existing structures. If this 
be so, to what can these structures be referred ? 
Until very recently the attempt was made to show that hairs 
and feathers were homologous in origin. Thus the older 
students sought to find intermediate stages in the pin feathers, 
which are certainly hair-like in appearance; and to derive 
both hair and feathers from the Reptilian scale, a view which 
received much seeming support from the tarso-metatarsal 
scales of birds and from the scale-like feathers of the penguins, 
as well as from the scaly armor of pangolins, etc., on the mam- 
malian side. The interested student will find all of these views 
ably and concisely summarized by Keibel; our space will not 
admit more than this reference to them. It may be said, how- 
ever, that Davies, to whom we owe the most accurate account 
of the development of the feather declines to regard pin feath- 
ers as the simplest type of the avian tegumentary covering but 
rather as a retrograde condition; and farther, that he regards 
the scales upon the tarsal and digital regions of birds a$ 
secondary formations, agreeing in this with Jeffries. 
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