1916] Chandler: Structure of Feathers 247 
on the structure and development of feathers have appeared, but 
need not be mentioned here. 
Throughout the literature, no general attempt has been made to 
use differences in the morphology of the minute structures of feath- 
ers as taxonomic or diagnostic characters. In a few cases where 
feathers differ macroscopically and obviously from the usual type, 
as in cassowaries and penguins, they have been considered as of 
taxonomic value, and the presence or absence, or degree of develop- 
ment, of the aftershaft has been so used. Jeffries (1884) realized 
that differences in the microscopic structures of feathers existed in 
different groups of birds, as shown by the following quotation from 
the paper cited: ‘‘The minute structures of these (wing and tail 
feathers) vary in different groups of birds, as I have myself observed, 
and has, I believe, been pointed out by Schroeder, though I have not 
seen his paper.’’ In Newton’s Dictionary of Birds, under the article 
on ‘‘Feather’’, is a similar statement as follows: ‘‘Cilia which are 
not furnished with hooks frequently have shapes which may possibly 
prove to be characteristic of different groups of birds’’. 
The only actual investigation of group differences in the micro. 
scopie structure of feathers was done by Mascha (1904). His work 
is accurate and suggestive as far as it goes, but he dealt only with 
the remiges of a very limited number of species, and, as would be 
expected from such a restricted survey, he missed entirely the taxo- 
nomic value of certain of the most characteristic features in the 
microscopic structure of feathers, and contributed but little towards 
our knowledge of the systematic and phylogenetic value of feather 
structures. 
In recent years considerable work has been done by zoologists in 
the study of the morphology and the taxonomic value of other 
integumentary structures of vertebrates, and their results point to 
the fact that such structures, though constantly in contact with the 
environment, and subject to more external influences than any other 
organs of the body, nevertheless possess phylogenetic characters which 
are remarkably constant and easily recognizable. 
The work of Toldt (1912) on the hair of mammals, like Mascha’s 
(1904) work on feathers, though only a beginning, is careful and 
accurate as far as it goes, and is highly suggestive in that it points 
the way to a field which is still almost untouched. Work along 
similar lines on the seales of reptiles has been done by Stehli (1910). 
His study was rather a general treatise on a few types, designed 
