148 
SEXUAL SELECTION: BIRDS. 
Part II. 
the other parts (see fig. 56), and this follows from the 
lower black mark of the elliptic ornament (h) having 
been originally thicker than the upper mark (c). Every 
step can be followed in the process 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, 6, 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 orna- 
ments. 
The successive steps in the shading of the ball-and- 
socket ocelli can be followed out wdth 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 
towards 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 espe- 
cially noticed), the line of separation being oblique, 
in the same direction with the bright coloured shades 
of the elliptic ornaments. Thus almost every minute 
detail in the shape and colouring of the ball-and-socket 
ocelli can be shewn to follow from gradual changes in 
the elliptic ornaments ; and the development 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 pecu- 
liarly ornamented. (Fig. 59.) The oblique longitudinal 
