160 THE AMERICAN NATURALIST [Vol. XLVII 



three distinct stages in the development of the young 

 bird's plumage before the adult color is reached. The 

 first two stages do not exhibit sexual dimorphism, nor are 

 they identical with that of the adult female. Sexual 

 dimorphism appears first in the third juvenile plumage. 

 At this stage, while the young female rather closely re- 

 sembles the adult female, the young males in their tout 

 ensemble are distinct from either the adult male or 

 female, though sometimes feathers like those of the fe- 

 male may be found. A study of the characters of the 

 Brown Leghorn capon or poullard, therefore, should show 

 whether their characters are juvenile, male or female. 

 For most characters, the results obtained from a pre- 

 liminary set of experiments are clear cut. 



Description of the Secondary Sexual Characters. — In 

 Table I is given a comparative statement of the more 

 pronounced secondary sexual characters common to 

 nearly all races of domestic chickens. There are other 

 differences between the sexes, which are more subtle and 

 therefore not considered here. In Table II are given 

 other secondary sexual characters found in the Brown 

 Leghorns but not in all other races of chickens. 



Comment on Tables. — Such exceptions to the general 

 statements given in Table I as occur, are mainly negative, 

 that is, they are characters which for one reason or 

 another do not become patent, as for example, the failure 

 of the whole or a part of the color pattern to become 

 visible, particularly in the case of uniformly colored 

 birds. 



In considering plumage characters aside from shape of 

 feather there are three features to be taken into account. 

 First, the localization of color in certain definite regions 

 of the body, thus forming the body pattern ; second, the 

 localization of color on definite regions of the feather, 

 forming the feather pattern ; third, the pigments them- 

 selves, which are associated with each pattern in various 

 ways. 



It is rather striking, that in spite of the numerous 



