Srrone. — Development of Color in Feathers. 
PLATE 6. 
All Figures are from feather germs of Sterna hirundo. 
Fig. 60. Transverse section showing first appearance of pigment granules in the 
cytoplasm of the pigment cell. X 1500. 
Figs. 31-384. Successive stages in development of pigment cells. Figures 31 and 
82 represent about the same stage. X 1500. 
Fig. 35. Pulp edge, or apex, of a ridge of the feather fundament, showing three 
pigment cells with granules crowded into an opaque mass and with 
processes beginning to be formed. X 1500. 
Fig. 36. A somewhat later stage, showing pigment granules or rods entering 
barbule cells (compare Plate 8, Fig. 17). > 1500. 
