1896.] 



NATURAL SCIENCES OF PHILADELPHIA. 



119 



of the terminal portion varies on different feathers, while the abra- 

 sion always takes place exactly to the line of demarcation of the 

 colors. 



In the bodyfeathers, the terminal part is less perfectly pennaceous 

 in structure than the base, and many of the barbs are entirely free 

 at their tips, which naturally makes them more liable to rapid 

 abrasion down to the point where the strongly pennaceous structure 

 begins.® This is particularly well seen in the Snow Bunting. A 



Fig. 1 . Tips of several barbs from 

 feather of Snow Bunting showing the 

 difierence in structure between the 

 light and dark portions (greatly en- 

 larged ) Photograph by Dr. A. P. 

 Brown. 



Fig. 2. Same, further enlarged, with 

 the barbs undisturbed showing the in- 

 terlocking of the barbules in the black 

 area. Somewhat diagrammatic, after 

 photograph by Dr. Brown. 



microscopical examination of these feathers, conducted at my request 

 by my friend Dr. A. P. Brown, shows further that the booklets on 

 these terminal parts are fewer in number and less perfectly de- 

 veloped, while the basal portion of the feather where the dark 

 pigment begins is thicker and probably tougher in structure, the 

 barbules and booklets being here well developed (Fig. 1 and 2). 



* A paper by Mr. Frank M. Chapman has appeared since the above was written 

 " On the Changes of Plumage in the Snowfiake, Plectrophenax niralis," Bull. 

 Amer. Mus. Nat. Hist , VIII, pp 9-12. In this he reaches exactly the same 

 conclusions as are here set forth by the writer and Dr. Brown, and the fact 

 that we were working entirely independently gives additional interest to the 

 statements. 



