Archive image from page 287 of The descent of man, and. The descent of man, and selection in relation to sex descentofmansele1889xdarw Year: 1889 266 The Descent of Man. Part II. were best able to hold her, have left the greatest number of progeny to inherit their respective 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 antenna of the female. In the male the modified antenna is either swollen in the middle or angularly bent, or converted (fig. 4) into an
Archive image from page 287 of The descent of man, and. The descent of man, and selection in relation to sex descentofmansele1889xdarw Year: 1889 266 The Descent of Man. Part II. were best able to hold her, have left the greatest number of progeny to inherit their respective 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 antenna 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 It serves, as I hear from Sir J. Lubbock, to hold the female, and for this same purpose one of the two posterior legs Q>) on the same side of the body is converted into a forceps. In another family the inferior or posterior antennae are ' curiously zigzagged' in the males alone. In the higher crustaceans the an- terior legs are developed into chela or pincers; and these are generally larger in the male than in the female, —so much so that the market value of the male, edible crab (Cancer pagurus), according to Mr. C. Spence Bate, is five times as great as that of the fe- male. In many species the chela 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 chela of the male often differ in structure (figs. 5, 6, and 7), the smaller one resembling that of the female. 'What advantage is Fig. 4. Labidocera 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 lemale. gained by their inequality in size on the opposite sides of the 8 ' Facts and Arguments for Darwin,' English translat. 1869, p. 20. See the previous discussion on the
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