. The descent of man, and selection in relation to sex. Evolution (Biology); Sexual selection in animals; Sexual dimorphism (Animals); Sex differences; Human beings. 34 SEXUAL SELECTION. [PartIL differ so mucli in appearance from the two great prolon- gations of the skull in C. bifurcus^ we can hardly doubt that they serve the same general purpose in the economy of these two animals. The first conjecture which will occur to every one is that they are used by the males for fighting together; but Dr. GUnther, to whom I am in- debted for the foregoing details, does not believe that such peaceable
. The descent of man, and selection in relation to sex. Evolution (Biology); Sexual selection in animals; Sexual dimorphism (Animals); Sex differences; Human beings. 34 SEXUAL SELECTION. [PartIL differ so mucli in appearance from the two great prolon- gations of the skull in C. bifurcus^ we can hardly doubt that they serve the same general purpose in the economy of these two animals. The first conjecture which will occur to every one is that they are used by the males for fighting together; but Dr. GUnther, to whom I am in- debted for the foregoing details, does not believe that such peaceable creatures would ever become pugnacious. Hence we are driven to infer tliat these almost monstrous devia- tions of structure serve as mascu- line ornaments. With many kinds of lizards, the sexes differ slightly in color, the tints and stripes of the males being Fia. 36.—Chamaelcon Owenii. Upper figure, male; brighter and lower figure, female. '^ -,• . more distinctly defined than in the females. This, for instance, is the case with the previously-mentioned Cophotis and "with the Acanthodactylus cajyensis of South Africa. In a Cordylus of the latter coimtry, the male is either much redder or greener than the female. In the Indian Calotes nigrilahris there is a greater difference in color between the sexes; the lips also of the male are black, while those of the female are green. In our common little vivij>arous lizard [Zootoca tu'vipara), " the umlcr side of the body and base of the tail in the male are bright orange, spotted with black; in the female these parts are. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Darwin, Charles, 1809-1882. New York, D. Appleton and company
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