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The Descent of Man

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differently coloured fowls, and the extraordinary<br />

variability <strong>of</strong> the ocelli on many Lepidoptera,<br />

lead us to conclude that their formation is<br />

not a complex process, but depends on some<br />

slight and graduated change in the nature <strong>of</strong><br />

the adjoining tissues.<br />

GRADATION OF SECONDARY SEXUAL<br />

CHARACTERS.<br />

[Fig. 54. Feather <strong>of</strong> Peacock, about two-thirds <strong>of</strong><br />

natural size, drawn by Mr. Ford. <strong>The</strong> transparent<br />

zone is represented by the outermost white<br />

zone, confined to the upper end <strong>of</strong> the disc.]<br />

Cases <strong>of</strong> gradation are important, as shewing<br />

us that highly complex ornaments may be acquired<br />

by small successive steps. In order to<br />

discover the actual steps by which the male <strong>of</strong><br />

any existing bird has acquired his magnificent<br />

colours or other ornaments, we ought to behold<br />

the long line <strong>of</strong> his extinct progenitors; but this<br />

is obviously impossible. We may, however,

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