Strong. — Development of Color in Feathers. 



PLATE 8. 



Photomicrographs. 



Fig. 39. Transverse section of blue-feather germ from Passerina cyanea. X 250. 

 Fig. 40. Transverse section of green-featiier germ from l^asserina oiris, showing 

 process of pigmentation of the barbules. X 157. 



I 



