EVOLUTION OF THE COLORS OF BIRDS. 327 



would result in the chestnut of D. bryanti, etc. This 

 leaves only the blue as a doubtful color, although it ap- 

 pears to be related to the black through gray. 



The following facts, shown by these plates, seem to be 

 inexplicable in any way except by the law of the assort- 

 ment of pigments, or else this law seems to account for 

 them most satisfactorily: (1) the specialized colors of the 

 males are generally the colors which, when combined, 

 would produce the generalized colors of the females; (2) 

 the specialized colors of the males when combined gen- 

 erally produce the generalized colors of the males; (3) 

 exactly the same color appears in widely separated parts 

 of the body of one species; (4) exactly the same color 

 often appears on the same or on different parts of the 

 body of different species; (5) in general, the same colors 

 run through the entire genus, however differently they 

 may be combined or modified in quantity or distribution. 



The following details concerning the proportion and 

 distribution of the different colors of the genus in the 

 adult male plumage may be of interest in this connec- 

 tion: Black is present in nineteen out of the twenty- 

 four species, being confined exclusively or mainly to the 

 upper parts of the body in four, and to the lower parts 

 in one species. The top of the head is solid black in 

 four species, the back mainly or entirely so in two, the 

 ear coverts in ten, throat in six, breast in three, and 

 sides in one. Yellow appears in eighteen species, being 

 confined to the upper parts of the body in two species 

 and to the lower parts in eight. The top of the head is 

 yellow in five species, the back never so. The rump 

 is yellow in four, ear coverts in four, throat in nine, and 

 breast in eleven. Olive or olive green occurs in thir- 

 teen species, being confined to the upper parts of the 

 body in all of them. Blue is present in eight species, 

 in all but one of them (D. ccerulea) being excluded from 



