98 THE AMERICAN NATURALIST [Vol. LII 



The pigment in all three phenotypes is black. The dif- 

 ferences in appearance are due to the distribution and 

 arrangement of the pigment or to its absence. 



The pigment in a black Andalusian feather is in the 

 form of rod- shaped granules, which almost completely fill 

 each cell. They extend to the very tips of both curved 

 and hooked barbules, and into the tiny hooklets given off 

 from the barbs of the latter class. The cell boundaries 

 are usually visible, due, apparently, to a slight contraction 

 of the pigment, leaving very narrow pigment-free spaces 

 between the cells. The former position of the nucleus of 

 each cell is almost always plainly visible, due to an accu- 

 mulation of pigment at its border, and to a narrow area 

 surrounding it that bears relatively little pigment. In 

 appearance, size and distribution the pigment granules in 

 feathers from the black Langshan seem to be identical 

 with those of black Andalusians. 



The feathers from blue Andalusians differ from those 

 of the blacks in two important particulars, namely, the 

 restriction of the pigment in the feather structure and the 

 shape of the granules. In blues of average shade, pig- 

 ment fails to appear in the extremities of the barbules of 

 both types. The hooklets are also entirely pigment-free. 

 Though not always the case, the curved barbules usually 

 carry rather more pigment than the hooked barbules, 

 since the pigment extends further toward the distal end. 

 As a usual thing that part of the hooked barbule which 

 bears the hooks is free from pigment and does not differ 

 in appearance, by transmitted light, from the same por- 

 tion of a similar barbule from a white feather. 



In the pigmented portions the pigment is usually mark- 

 edly contracted or clumped within each cell, leaving a 

 pigmentless space about the border much wider than is 

 the case with blacks. These spaces are not always clean 

 cut, but may be broken by invading rows of granules, or 

 isolated granules may be found scattered within them. 

 As a usual thing the nuclear boundaries in the cells of 

 blue-gray feathers can only be made out with difficulty, 

 if at all. 



