. The descent of man : and selection in relation to sex. Evolution; Natural selection; Heredity; Human beings. 266 The Descent of Man. Part II. were best able to hold her, have left the greatest number of progeny to inherit their respective advantages.^ In some of the lower crustaceans, the right anterior antenna of the .male differs greatly in structure from the left, the latter resembling in its simple tapering joints the antennsB of the female. In the male the modified antenna is either swollen in the middle or angularly bent, or converted (fig. 4) into an elegant, and sometimes wonderfully
. The descent of man : and selection in relation to sex. Evolution; Natural selection; Heredity; Human beings. 266 The Descent of Man. Part II. were best able to hold her, have left the greatest number of progeny to inherit their respective advantages.^ In some of the lower crustaceans, the right anterior antenna of the .male differs greatly in structure from the left, the latter resembling in its simple tapering joints the antennsB of the female. In the male the modified antenna is either swollen in the middle or angularly bent, or converted (fig. 4) into an elegant, and sometimes wonderfully complex, prehensile organ.^ It serves, as I hear from Sir J. Lubbock, to hold the female, and for this same purpose one of the two posterior legs (6) on the same side of the body is converted into a forceps. In another family the inferior or . posterior antennsB are '' curiously zigzagged" in the males alone. In the higher crustaceans the an- terior legs are developed into chelae or pincers; and tlicse are generally larger in the male than in the female, —so much so that the market value of the male edible crab (^Caiicer jpagurus), according to IMr. C. Spence Bate, is five times as great as that of the fe- male. In many species the chelse are of unequal size on the opposite side of the body, the right-hand one being, as I am informed by Mr. Bate, generally, though not invariably, the largest. This inequality is also often much greater in the male than in the female. The two chelae of the male often differ in structure (figs. 5, 6, and 7), the smaller one resembling that of the female. What advantage is gained by their inequality in size on the opposite sides of the. 4. LabWocera Darwinii (from Lubbock). a. Part of right anterior an- tenna of male, forming a prehensile organ. b. Posterior pair of thoracic legs of male. c. Ditto of temale. * * Facts and Arguments for Darwin,' English translat. 1869, p. 20. See the pi-evious discussion on the olfactory threads. Sars has de
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