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The Descent of Man

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and the young <strong>of</strong> the sparrow <strong>of</strong> Palestine (P.<br />

brachydactylus), as well as <strong>of</strong> some allied species.<br />

We may therefore assume that the female<br />

and young <strong>of</strong> the house-sparrow approximately<br />

shew us the plumage <strong>of</strong> the progenitor <strong>of</strong> the<br />

genus. Now with the tree-sparrow (P. montanus)<br />

both sexes and the young closely resemble<br />

the male <strong>of</strong> the house-sparrow; so that they<br />

have all been modified in the same manner,<br />

and all depart from the typical colouring <strong>of</strong><br />

their early progenitor. This may have been effected<br />

by a male ancestor <strong>of</strong> the tree-sparrow<br />

having varied, firstly, when nearly mature; or,<br />

secondly, whilst quite young, and by having in<br />

either case transmitted his modified plumage to<br />

the females and the young; or, thirdly, he may<br />

have varied when adult and transmitted his<br />

plumage to both adult sexes, and, owing to the<br />

failure <strong>of</strong> the law <strong>of</strong> inheritance at corresponding<br />

ages, at some subsequent period to his<br />

young.

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