. The descent of man, and selection in relation to sex. Evolution (Biology); Sexual selection in animals; Sexual dimorphism (Animals); Sex differences; Human beings. 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;48 and something of the same kind may be observed A a*. Bl B Fig. 52.—Cyllo leda, Linn., from a drawing by Mr
. The descent of man, and selection in relation to sex. Evolution (Biology); Sexual selection in animals; Sexual dimorphism (Animals); Sex differences; Human beings. 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;48 and something of the same kind may be observed A a*. Bl B Fig. 52.—Cyllo leda, Linn., from a drawing by Mr. Trimcn, 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. A1. Specimen, from Natal, ditto. B1. 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. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Darwin, Charles, 1809-1882. New York: D. Appleton and Company
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