116 DWIGHT 



The part that age plays in dichromatism, albinism, melanism, 

 etc., is one as yet little understood and also offers an inviting 

 field for investigation. 



Beyond the second nuptial plumage it is not possible to 

 trace the age of a bird, for the second postnuptial moult removes 

 the last tell-tale feathers that in a few individuals of a few highly 

 colored species have survived earlier moults. Whether more 

 careful study of a greater number of species will show age 

 characters of plumage persistent to seventh or eighth stages, I 

 cannot say, but so far as the Passerine species of eastern North 

 America are concerned I feel confident that the usual time as- 

 signed for the acquisition of adult plumage has been greatly 

 overestimated. 



V. COLOR FACTS 7's. COLOR THEORIES 



The number of investigators who have studied feathers, ever 

 since the days of Aristotle, is almost incredible. All general 

 works deal with plumages, while a number of special papers on 

 feather development, feather structure, moult and color are 

 worthy of particular mention, among them those of Meckel 

 ('15), Dutrochet ('19), Cuvier ('25), Bachman ('39), Geoffroy 

 Saint-Hilaire ('41), Schlegel ('52), Homeyer ('53), Gatke ('54 

 and '91), Meves ('55), Engel ('56), Holland ('60 to '64), Fatio 

 ('66), Stieda ('69), Samuel ('70), Pernitza ('71), Studer l^'y^ and 

 •78), Palmen ('80), Klee ('86), Davies ('88 and '89), Ficalbi 

 ('90), Gadow ('9i-'93), Maurer ('92 and '95), Meijere ('95), 

 Stone ('96) and Keibel ('96). Besides these writers there are 

 some who have studied color and pigment especially, and among 

 these may be mentioned Gloger ('53), Altum ('54 and '55), 

 Weinland ('56-' 59), Bogdanow ('58), Severtzov ('63), Kruken- 

 berg ('81), Jeffries ('82), Gadow ('82) and Rabl (97). Still 

 others (including some of those already cited) have discussed 

 the theory that a feather once grown could be recolored months 

 afterward, an idea that seems to have originated with Cartwright 

 (1792); to have been advanced by Fleming ('17 and '20), 

 Whitear ('18), Ord ('30), Yarrell ('33 and '35), Schlegel ('52) 



