STRONG: DEVELOPMENT OF COLOR IN DEFINITIVE FEATHER. 185 



EXPLANATION OF PLATES. 



Figures 12-21 and 23 are from sections of a featlier germ (secondary) of Sterna 

 hirundo which was fixed with Hermann's fluid and stained in iron haematoxylin. 

 They represent corresponding regions, indicated in Figure "2 by an asterisk (*),— 

 but taken at diflferent levels. The levels of the sections are indicated in Figure 1 

 by the horizontal lines 12, 13, 14, etc. Figures 3, 35, 36, and 37 are also from 

 material fixed in Hermann's fluid and stained with iron haematoxylin. Figures 

 22, 24, 38, 39, 40, 41, 42 were made from material fixed with Kleinenberg's picro- 

 sulphuric mixture and stained in Kleinenberg's haematoxylin followed by eosin. 

 All drawings were made with the aid of a camera lucida. 



ABBREVIATIONS. 



