Archive image from page 436 of The descent of man . The descent of man : and selection in relation to sex descentofmanseledarw Year: 1874 OCELLI. 423 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 towards a central point from a surrounding zone, which latter 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 surround- ing darker zone. In either case an ocellus is the result. The Fig
Archive image from page 436 of The descent of man . The descent of man : and selection in relation to sex descentofmanseledarw Year: 1874 OCELLI. 423 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 towards a central point from a surrounding zone, which latter 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 surround- ing darker zone. In either case an ocellus is the result. The Fig. 53. Cyllo leda, Linn., from a drawing by Mr. Trimen, showing the extreme range of variation in the ocelli. A. Specimen, from Mauritius, up- per surface of fore-wing. A. Specimen, from Natal, ditto. B. Specimen, from Java, upper surface of hind-wing. B. Specimen, from Mauritius, ditto. coloring matter seems to be a nearly constant quantity, but is redistributed, either centripetally or centrifugally. The feathers of the common guinea-fowl offer a good instance of white spots surrounded by darker zones; and wherever the white spots are large and stand near each other, the surrounding dark zones become confluent. In the same wing-feather of the Argus pheas- ant dark spots may be seen surrounded by a pale zone, and white spots by a dark zone. Thus the formation of an ocellus in its most elementary state appears to be a simple affair. By what further steps the more complex ocelli, which are surrounded by many successive zones of color, have been generated, I will not pretend to say. But the zoned feathers of the mongrels from dif- ferently colored fowls, and the extraordinary variability of the
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