METALLIC COLORS OF FEATHERS FROM NECK OF PIGEON. 87 



angles of incidence were small, the predominant colors were yel- 

 low and green, especially green. On the margins where the 

 angles of incidence were great, the prevailing colors were reds 

 and purples. 



The colors of the feathers described, when observed without a 

 microscope, are very apparently mixed colors. The greenish ef- 

 fects are produced when light strikes the broad surfaces of the 

 barbules and is reflected with a small angle of reflection. The reds 

 appear only when light falls with a large angle of incidence on 

 the pigment granules of a margin or elevated portion of a barbule. 



We seem to have a clear case of Newton's rings where, each 

 pigment granule comes in contact with the outer transparent 

 layer. 



This is a preliminary statement of my results. Another paper 

 describing them in greater detail with the aid of figures is in 

 process of publication. 

 APRIL i, 1902. 



BIBLIOGRAPHY. 



Altum, B. 



'54. Ueber den Bau der Federn als Grund ihrer Farbung. journ. 1'iir Ornith. , Bd. 



2, pp. xix-xxxv. 

 Altum, B. 



'54a. Ueber die Farben der Vogelfedern im Allgemein, iiber das Schillern insbeson- 

 dere. Naumannia, Jahrg. 1854, pp. 293-^,04. 



Brucke, E. 



'61. Uber den Metallglanz. Sitzungsberichte d. Kais. Akad. in Wien. Math. 



Naturw. Classe, Bd. 43, Abth. 2, pp. 177-192. 

 Haecker, V. 



'90. Ueber die Farben der Vogelfedern. Arch. f. mik. Anat., Bd. 35, pp. 68-87, 

 Taf. 4. 



