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The Descent of Man

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egard to the young differing greatly from both<br />

sexes in their adult summer and winter plumages,<br />

this occurs with some herons and egrets <strong>of</strong><br />

North America and India,—the young alone<br />

being white.<br />

I will make only a few remarks on these complicated<br />

cases. When the young resemble the<br />

females in their summer dress, or the adults <strong>of</strong><br />

both sexes in their winter dress, the cases differ<br />

from those given under Classes I. and III. only<br />

in the characters originally acquired by the males<br />

during the breeding-season, having been<br />

limited in their transmission to the corresponding<br />

season. When the adults have a distinct<br />

summer and winter plumage, and the young<br />

differ from both, the case is more difficult to<br />

understand. We may admit as probable that the<br />

young have retained an ancient state <strong>of</strong> plumage;<br />

we can account by sexual selection for the<br />

summer or nuptial plumage <strong>of</strong> the adults, but<br />

how are we to account for their distinct winter

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