58 The Bird 
or spotted feathers assume most intricate and complex 
colour masses and patterns. 
Darwin illustrates this very plainly in the case of the 
Argus Pheasant, and pays a fitting tribute to the evolu- 
tion of the marvellous colour patterns among birds. ‘The 
ocelli on the wing-feathers of the Argus Pheasant are 
shaded in so wonderful a manner as to resemble balls 
lying loose within sockets. That these ornaments should 
have been formed through the selection of many succes- 
sive variations, not one of which was originally intended 
to produce the ball-and-socket effect, seems as incredible 
as that one of Raphael’s Madonnas should have been 
formed by the selection of chance daubs of paint made by 
a long succession of young artists, not one of whom in- 
tended at first to draw the human figure. In order to 
discover how the ocelli have been developed we cannot 
look to a long line of progenitors, nor to many closely 
allied forms, for such do not now exist. But fortunately 
the several feathers on the wing suffice to give us a clue 
to the problem, and they prove to demonstration that a 
graduation is at least possible from a mere spot to a 
finished ball-and-socket ocellus.”’ 
Two feathers from the wing of a Vulturine Guinea- 
fowl have been chosen to illustrate a more simple but 
no less beautiful colour evolution. On the less exposed 
side of one of the feathers are three or four series of irregu- 
lar white spots which tend in places to form transverse 
bands. On the opposite side of the shaft near the tip 
these spots are still distinct, but as our glance passes 
gradually toward the base of the feather, the spots con- 
