A STUDY OF FUNDAMENTAL BARS IN FEATHERS. 



OSCAR RIDDLE. 



The structure and development of feathers have been studied 

 by many investigators. The pigments of feathers have also 

 been the subject of a very great number of researches. In spite, 

 however, of these numerous studies of feather structures and 

 pigments, we know almost nothing of structural differences be- 

 tween pigmented and non-pigmented areas, and nothing at all 

 of the causes which lead to the orderly and definite distribution 

 of pigment into the often complex color-patterns commonly 

 found in birds. In connection with a research directed to these 

 two points it was thought advisable to make a study of certain 

 defects which were known to appear occasionally in feathers. 

 It is a preliminary account of my results in this more restricted 

 field which, however, proved to be a rather significant one 

 that is to be found in this paper. The work was undertaken in 

 1904 under the direction of Professor C. O. Whitman in the 

 zoological laboratory of the University of Chicago. It is a 

 pleasure to acknowledge the help, encouragement and criticism 

 which Professor Whitman has given in connection with this work. 



At the time I took up the study of the defects under consid- 

 eration, they had been reported but once, and this report had to 

 do with but a single specimen, a single plumage, and a single 

 defect in each feather. This was an account by R. M. Strong l 

 of "A Case of Abnormal Plumage" found in a hybrid pigeon. 

 Dr. Strong described and figured two types of abnormalities, and 

 concurred with Professor Whitman, who had reared the bird, in 

 the opinion that the defects were probably caused by malnutrition 

 during the growth of the Juvenal plumage. Besides this case, 

 Professor Whitman had observed these or similar defects in the 

 feathers of several of his birds, and my problem was to learn the 

 extent of their occurrence and to determine their cause. In 

 the course of my studies I have found still other abnormalities 



BIOLOGICAL BULLETIN, November, 1902. 



165 



