The Development of Color in the Definitive Feather. By R. M. 
STRONG. 
TABLE OF CONTENTS. 
PAGE PAGE 
I. Introduction . . . .« « . 147, IV. The production of color in 
II. Methods and material . . . 148 the feather. . . 161 
III. The development of the V. The pigmentation of ‘the 
REGGMeE s)he ese POE feather) 3) ’s |. . 163 
A. Thefeathergerm . . 151 A. The chemical tana! of 
B. The differentiation of ihe feather pigments. . . 163 
PCA MEE wh eis is.) s) 1 266 B. The origin of pigment. . 164 
1 The: barbales)../ ya). 108 C. The distribution of. pig- 
Z, “Lhe'barbieels, 3.5 - s 1o7 ment in feathers . . . 168 
S The barry. . ... 6. 168) VI. Change of color’ without 
4. The rhachis.’ 7°.) .' .. 160 WONG! se! SP SU, he Ee 
5» s The resiaualicella.. (5 9. 160) VIE: Summary): 202030002 216 
6. Cornification and with- Binligaraphiys sdf 2008 ah caeea ety LES 
drawal of the feather . 161 
I. Introduction. 
The more or less striking variations in color exhibited by many 
species of birds at different seasons of the year have been a fruitful 
theme for discussions and speculation among ornithologists. Numerous 
cases of change of color not apparently connected with the ordinary 
process of molt have been reported from time to time. A theory of . 
change of color without molt was the subject of a rather warm con- 
troversy about the middle of the nineteenth century, and there has been 
something of a revival of the discussion in the last few years. 
It has seemed to me that a solution of the problem could not be 
attained without a thorough consideration of the causes of color and its 
development. 
The present work was begun in the fall of 1899 under the direction 
of Professor E. L. Mark in the Zodlogical Laboratory at Harvard 
University. I wish here to acknowledge my great indebtedness to 
VOL. XL. —NO. 3 1 
