128 



SEXUAL SELECTION: BIRDS. 



[Part II. 



With birds and 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 ; 46 and something of the same kind may be observed 



A A* 



Fig. 52. — Cyllo Ieda, Linn., from a drawing- by Mr. Trimen, showing the extreme 



range of variation in the ocelli. 



A Specimen, from Mauritius, upper B. Specimen, from Java, upper surface 



surface of fore-wing. ' of hind-wing. 



A 1 . Specimen, from Natal, ditto. B 1 . Specimen, from Mauritius, ditto. 



in the two sexes of the Argus pheasant. However this 

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

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

 matter being drawn, toward a central point from a sur- 

 rounding zone, which 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, either 



46 Jerdon, 'Birds of India,' vol. iii. p. 517. 



