538 THE AMERICAN NATURALIST [Vol. LIV 



" pelvic wing" is clearly illustrated in two photographic 

 figures of four weeks old White Leghorn chicks in Eice, 

 Nixon and Koger's (1908, pp. 25-26, Figs. 6 and 7) paper 

 on "The Molting of Fowls." The structure is referred 

 to by these writers as "the thigh tract." 



In chickens the "pelvic wing" occurs along the pos- 

 tero-ventral border of the femoral or lumbar tract, as 

 described by Nitzsch (1867, Plate VII, Fig. 6) for Gallus 

 bankiva and appears to be a part of it. In its develop- 

 ment it is synchronous with, or slightly preceded by, the 

 feathers of the humeral tract and has so much in com- 

 mon with the latter as to suggest that the two tracts may 

 be homologous structures of the hind and fore-limbs, re- 

 spectively. The "pelvic wing" extends across the upper 

 part of the hind limb and a more or less well-marked 

 patagium just behind the femur. The humeral tract ex- 

 tends across the upper part of the fore limb and the 

 patagium behind the humerus. 



The appearance of the "pelvic wing" of chicks of dif- 

 ferent breeds is shown in Plate I, Figs. 1, 3, 4, 5, 6, and 7. 



The structure in the Bronze turkey (Fig. 2) is essen- 

 tially the same as in chickens. This breed is the largest 

 and commonest variety of domestic turkeys and most 

 nearly resembles their native wild progenitors. 



In the waterfowl the structure has not been found. 

 This was perhaps to be expected from the figures of 

 Nitzsch (1867, Plate X, Figs. 5, 6, and 7). The birds ob- 

 served were domesticated Mallard ducks and White 

 Embden geese. In neither could any feathers be discov- 

 ered which were set off from the others of the femoral 

 tract, either in size, or precocity of development. There 

 is however in both species a group of feathers whose de- 

 velopment is simultaneous with that of the feathers of 

 the humeral tract. These are situated on a branch of the 

 inferior tract which extends beyond the breast along the 

 sides of the trunk almost to the knee. The feathers of 

 both these tracts precede the remiges in development. 



Nitzsch (1867, p. 146) makes note of the fact that "this 



