1916] Chandler: Structure of Feathers 385 
(8) Proximal barbules of outer vane of remiges without ventral 
cilia except at extreme tip of barbs, or with a sudden transition at 
about middle of barb. 
(9) Looser body feathers with barbules very much reduced and 
simplified, with all barbicels rudimentary or absent except two or 
three hooklets on distals. 
(10) Down barbules with lobate or fingerlike villi on base, the 
pennulum with more or less distinct nodes, the latter not strikingly 
larger near base of barbules. 
IV GENERAL CONCLUSIONS 
1. Taxonomic Value of the Structure of Feathers 
The systematic study of the structure of feathers of different 
groups of birds which has been made and presented in the preced- 
ing pages cannot but impress one with the fact that the morphology 
of feathers, in other words, the epiphyology of birds, is as valuable 
from a taxonomic point of view as is osteology, myology, or the 
systematic morphology of any other organ or system of organs of 
the body. Not only is the difference between birds of different 
groups of larger content as clearly marked in the structure of their 
feathers as in the structure of any other system of organs, but the 
fact that most of the modifications in these minute details of 
structure which are found in different groups of birds can be of 
little or no adaptive value, increases the taxonomic value beyond 
that possessed by most other organs, since parallel or convergent 
adaptive evolution is largely eliminated. As in all other organs, 
parallel evolution which is not necessarily correlated with adapta- 
tion may take place, and undoubtedly has done so, with the result 
that the structure of feathers alone is not a safe criterion of rela- 
tionship any more than is the structure of the bones or muscles. 
Taken in conjunction with the evidence furnished by other organs 
and systems of organs, however, and with these as a general guide, 
the cases of parallelism in evolution can in most cases be discov- 
ered, and the evidences of relationship and phylogenesis furnished 
by the morphology of feathers is then of the very highest value. 
As has been pointed out by Cockrell (191la), the scales of 
fishes are unquestionably of great taxonomic value. Work on the 
