142 SEXUAL SELECTION: BIRDS. [Part II. 



cess of confluence and modification; and the black ring 

 which surrounds the ball of the ocellus is unquestionably 

 formed by the union and modification of the three black 

 marks, b, c, d, of the elliptic ornament. The irregular 

 zigzag black marks between the successive ocelli (see 

 again Fig. 56) are plainly due to the breaking up of the 

 somewhat more regular but similar marks between the 

 elliptic ornaments. 



The successive steps in the shading of the ball-and- 

 socket ocelli can be followed out with equal clearness. 

 The brown, orange, and pale-leaden narrow zones which 

 border the lower black mark of the elliptic ornament can 

 be seen gradually to become more and more softened and 

 shaded into each other, with the upper lighter part toward 

 the left-hand corner rendered still lighter, so as to become 

 almost white. But even in the most perfect ball-and- 

 socket ocelli a slight difference in the tints, though not in 

 the shading, between the upper and lower parts of the 

 ball can be perceived (as was before especially noticed), 

 the line of separation being oblique, in the same direction 

 with the bright-colored shades of the elliptic ornaments. 

 Thus almost every minute detail in the shape and coloring 

 of the ball-and-socket ocelli can be shown to follow from 

 gradual changes in the elliptic ornaments; and the de- 

 velopment of the latter can be traced by equally small 

 steps from the union of two almost simple spots, the lower 

 one (Fig. 57) having some dull fulvous shading on the 

 upper side. 



The extremities of the longer secondary feathers which 

 bear the perfect ball-and-socket ocelli are peculiarly orna- 

 mented. (Fig. 59.) The oblique longitudinal stripes 

 suddenly cease upward and become confused, and above 

 this limit the whole upper end of the feather (a) is covered 

 with white dots, surrounded by little black rings, stand- 

 ing on a dark ground. Even the oblique stripe belonging 



