58 The Bird 



or spotted feathers assume most intricate and complex 

 coloiu' masses and j)at terns. 



Darwin illustrates this very plainly in the case of the 

 Argus Pheasant, and jniys a lilting tribute to the evolu- 

 tion of tlio Tnar\ellous 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 ))cen formed through the selection of man}' 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 tlie selection of chance daubs of paint made by 

 a long succession of >'oung artists, not one of whom in- 

 tended a I first to diaw the human figure. In order to 

 discover how the ocelli have been developed we cannot 

 look to a long line of progenitors, nor to manv closelv 

 allied forms, for such do not now exist. But fortunately 

 the several feathers on the wing suffice to gi\'e us a clue 

 to the })rol)lem, and they pro\'e to demonstration that a 

 graduation is at least j)ossible 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 

 gradual!}- toward the base of the feather, the spots con- 



