1916] Chandler: Structure of Feathers 279 



I can think of no more striking example of isotely, the attainment 

 of the same end by different methods in different groups, than 

 these manifold methods of producing a single color. 



2. Effect of Albinism on Structural Color Modifications 



One of the most remarkable things about the morphology of 

 feathers is the profound change of structure so frequently involved 

 in the production of color effect, in spite of the surprising con- 

 stancy of group characters where no such color modifications occur. 

 It was with extreme interest that the writer examined some of the 

 feathers of an albino mallard. Anas platyrhynchos, to see whether 

 the morphologic modifications involved in the production of the 

 violet speculum would be lost or retained with the lack of pig- 

 ment. It was found that the distal barbules of the outer vane, 

 which in a normal mallard have the pennula highly modified for 

 the production of color (pi. 21, fig. 28a), lacked this modification 

 entirely, and were exactly similar to the normal distal barbules of 

 the outer vane of feathers of this species in which there was no 

 modification for color (pi, 21, fig. 28e). In other words, the con- 

 stitutional factor causing the morphologic specialization of feather 

 structures for the production of color is inseparably hound together 

 with the factor for the accompanying pigment, and if the latter is 

 absent, the feather structures present the normal type of the species 

 in which there are no color modifications. 



