494 



THE DESCENT OF MAN. 



these ornaments should have been formed through the selec- 

 tion of many successive variations, not one of which was 

 originally intended to produce the "ball-and-socket effect, 

 seems as incredible as that one of Eaphears Madonnas 

 should have been formed by the selection of chance daubs 



of paint made by a long 

 ABC succession of young art- 

 ists, not one of whom 

 intended 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 clew to the problem, 

 and they prove to dem- 

 onstration that a gra- 

 dation is at least pos- 

 sible from a mere spot 

 to a finished ball-and- 

 socket ocellus. 



The wing - feathers, 

 bearing the ocelli, are 

 covered with dark 

 stripes (fig. 57) or 

 with rows of dark spots 

 (fig. 59), each stripe or 



Fig. 57. Part of secondary wing-feather of rnw n f Rnn f R riinni no- 

 Argus pheasant, showing two perfect ocelli, r W OI SpOIS 

 a and b. A, B, C, D, etc., are dark stripes obliquely down the 

 running obliquely down, each to an ocellus. outer gide of the shaft 



[Much of the web on both sides, especially . < ji . 



to the left of the shaft, has been cut off.] to One 01 the 



The spots are gen- 



erally elongated in a line transverse to the row in which 

 they stand. They often become confluent either in the line 

 of the row and then they form a longitudinal stripe or 

 transversely, that is, with the spots in the adjoining rows, 

 then they form transverse stripes. A spot sometimes 



