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The Descent of Man

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It is impossible to decide which <strong>of</strong> these three<br />

modes has generally prevailed throughout the<br />

present class <strong>of</strong> cases. That the males varied<br />

whilst young, and transmitted their variations<br />

to their <strong>of</strong>fspring <strong>of</strong> both sexes, is the most probable.<br />

I may here add that I have, with little<br />

success, endeavoured, by consulting various<br />

works, to decide how far the period <strong>of</strong> variation<br />

in birds has generally determined the transmission<br />

<strong>of</strong> characters to one sex or to both. <strong>The</strong> two<br />

rules, <strong>of</strong>ten referred to (namely, that variations<br />

occurring late in life are transmitted to one and<br />

the same sex, whilst those which occur early in<br />

life are transmitted to both sexes), apparently<br />

hold good in the first (34. For instance, the males<br />

<strong>of</strong> Tanagra aestiva and Fringilla cyanea require<br />

three years, the male <strong>of</strong> Fringilla ciris four<br />

years, to complete their beautiful plumage. (See<br />

Audubon, 'Ornith. Biography,' vol. i. pp. 233,<br />

280, 378). <strong>The</strong> Harlequin duck takes three years<br />

(ibid. vol. iii. p. 614). <strong>The</strong> male <strong>of</strong> the Gold<br />

pheasant, as I hear from Mr. Jenner Weir, can

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