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The Descent of Man

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autumn <strong>of</strong> their first year.) In mankind, and<br />

even as low down in the organic scale as in the<br />

Lepidoptera, the temperature <strong>of</strong> the body is<br />

higher in the male than in the female, accompanied<br />

in the case <strong>of</strong> man by a slower pulse.<br />

(30. For mankind, see Dr. J. Stockton Hough,<br />

whose conclusions are given in the 'Popular<br />

Science Review,' 1874, p. 97. See Girard's observations<br />

on the Lepidoptera, as given in the<br />

'Zoological Record,' 1869, p. 347.) On the whole<br />

the expenditure <strong>of</strong> matter and force by the two<br />

sexes is probably nearly equal, though effected<br />

in very different ways and at different rates.<br />

From the causes just specified the two sexes can<br />

hardly fail to differ somewhat in constitution,<br />

at least during the breeding-season; and, although<br />

they may be subjected to exactly the<br />

same conditions, they will tend to vary in a<br />

different manner. If such variations are <strong>of</strong> no<br />

service to either sex, they will not be accumulated<br />

and increased by sexual or natural selec-

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