128 



SEXUAL SELECTION: BIRDS. 



[I'art II. 



With birtls ami many other animals it seems, from the 

 comparison of allied species, to follow, that circular spots 

 are often generated by the breaking up and contraction 

 of stripes. In the Tragopan pheasant faint white lines in 

 the female represent the beautiful white spots in the 

 male • " and something of the same kind may be observed 



A A' 



Fig. 52. — Cyllo leda, Liun., from a flrawinij liy Mr. Trimen, ehowing the extreme 

 range of variation in tlie ocelli. 

 A. Specimen, from Mauritins, upper B. Specimen, from Java, npper surface 



piirface of fore-wing. of hind-wing. 



A'. Specimen, from Natal, ditto. B'. Specimen, from Mauritius, ditto. 



in the two sexes of the Argus pheasant. However this 

 may be, ajipearances strongly favor the belief that, on the 

 one liand, a dark spot is often formed by the coloring 

 matter being drawn toward a central point from a sur- 

 rounding zone, Avhich is thus rendered lighter. And, on 

 the other hand, that a white spot is often formed by the 

 color being driven away from a central point, so that it 

 accumulates in a surrounding darker zone. In either case 

 an ocellus is the result. The coloring matter seems to be 

 a nearly constant quantity, but is redistributed, cither 



*' Jcrdon, 'Birds of India,' vol. iii. p. 517. 



