°i8q7 1 Chadbourne on Iiidiiudnal Dichromatism. 9 C 



black, and at least two varieties of brownish coloring matter 

 (so-called ' pigments '), were present, not only after the red-brown 

 shade appeared in the plumage, but also in every feather of the 

 gray type, except three of the ' first ' and one from the mature 

 gray plumage. 



The black pigviented matter was made up of oblong-oval or ellip- 

 tical granules, never of small rods, as in the domestic pigeon ; 

 but it is well-known that the shape varies in different kinds of 

 birds. The amount of black granular matter was always rela- 

 tively small, and it was chiefly confined to the deeper cell layers. 

 Isolated spots of true black were frequent in the central cells, 

 while around them there was often much dark brown. 



The bro7Vfi pigmented tnaterial wdt-S found in the form of a pale, 

 nongranular, diffused stain, extending through all kinds of feather 

 tissue ; and also as brown granules, of various tints and sizes, 

 which were usually in narrow lines or groups, instead of being 

 generally distributed, like the nongranular stain. The two 

 extremes were connected by a complete series of intermediate 

 forms, showing every gradation between the dark chocolate and 

 the ochraceous tint ; while the size of the granules also varied 

 considerably, and it was at times not easy to distinguish the homo- 

 geneous from the very finely granular. The black and very dark 

 brown granules perhaps also intergrade, but on this point I can. 

 not speak with certainty. 



As the red phase developed, more and more red-brown granules 

 and diffuse stain seemed to be present in the feathers, at times 

 obscuring, or completely hiding the dark markings beneath (Plate 

 I, fig. i), or grouped and scattered about the black in the deeper 

 layers, caused various shades and tints of brown and tawny. As a 

 rule the seemingly black color proved to be the result of either a 

 dense mass of dark brown granules, of the greater thickness of the 

 darker portion of the specimen, or of both continued, plus an un- 

 derlying area of true black in the deep tissues. The pure rufous and 

 bright tawny portions had the coloring matter chiefly in the more 

 superficial cell layers, and either little or no true black beneath ; 

 while the streaks and lines of brownish granules suggested the 

 ' bast-fibre layer ' of certain plants, and the tawny effect was 

 heightened by the diffuse nongranular stain (Plate I, fig. 4, b 



