. The descent of man, and selection in relation to sex. Evolution; Natural selection; Heredity; Human beings; Sexual selection in animals; Sexual dimorphism (Animals); Sex differences. Insects 337 two sexes in above a hundred species of the Copridae, did not lind any marked difference in this respect among well- developed individuals. In Lethrus, moreover, a beetle belonging to the same great division of the Lamellicorns, the males are known to fight, but are not provided with horns, though their mandibles are much larger than those of the female. The conclusion that the horns have been acquir
. The descent of man, and selection in relation to sex. Evolution; Natural selection; Heredity; Human beings; Sexual selection in animals; Sexual dimorphism (Animals); Sex differences. Insects 337 two sexes in above a hundred species of the Copridae, did not lind any marked difference in this respect among well- developed individuals. In Lethrus, moreover, a beetle belonging to the same great division of the Lamellicorns, the males are known to fight, but are not provided with horns, though their mandibles are much larger than those of the female. The conclusion that the horns have been acquired as prnaments is that which best agrees with the fact of their having been so immensely, yet not fixedly, developed—as shown by their extreme variability in the same species, and by their extreme diversity in closely-allied species. This view will at first appear extremely improbable; but we shall. Fiff. 21. Figr. 23. Fig. 21. Onitis furcifer. male viewed from beneath. Fig. 22. Left-hand figure, male of Onitis furcifer, viewed laterally. Right- hand figure, female, a. Rudiment of cephalic horn, b. Trace of thoracic horn or crest. hereafter find with many animals standing much higher in the scale, namely fishes, amphibians, reptiles and birds, that various kinds of crests, knobs, horns and combs have .been developed apparently for this sole purpose. I The males of Onitis furcifer (fig. 21), and of some other species of the genus are furnished with singular projections on their anterior femora, and with a great fork or pair of horns on the lower surface of the thorax. Judging from other insects, these may aid the male in clinging to the female. Although the males have not even a trace of a horn on the upper surface of the body, yet the females plainly ex- hibit a rudiment of a single horn on the head (fig. 23, a) and of a crest {h) on the thorax. That the slight thoracic crest in the female is a rudiment of a projection proper to the male, though entirely absent in the male o
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Keywords: ., bookcentury1800, bookdecade1870, booksubjecthumanbeings, bookyear
