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The Descent of Man

The Descent of Man

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<strong>of</strong> such importance that they have been placed<br />

under distinct genera or even families, yet the<br />

differences do not seem <strong>of</strong> the kind which can<br />

be safely attributed to sexual selection. <strong>The</strong>se<br />

animals are <strong>of</strong>ten beautifully coloured, but as<br />

the sexes do not differ in this respect, we are<br />

but little concerned with them. Even the Nemertians,<br />

though so lowly organised, "vie in<br />

beauty and variety <strong>of</strong> colouring with any other<br />

group in the invertebrate series"; yet Dr. McIntosh<br />

(6. See his beautiful monograph on 'British<br />

Annelids,' part i. 1873, p. 3.) cannot discover<br />

that these colours are <strong>of</strong> any service. <strong>The</strong> sedentary<br />

annelids become duller-coloured, according<br />

to M. Quatrefages (7. See M. Perrier: 'L'Origine<br />

de l'Homme d'apres Darwin,' 'Revue<br />

Scientifique', Feb. 1873, p. 866.), after the period<br />

<strong>of</strong> reproduction; and this I presume may be<br />

attributed to their less vigorous condition at<br />

that time. All these worm- like animals apparently<br />

stand too low in the scale for the individuals<br />

<strong>of</strong> either sex to exert any choice in selec-

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