. The descent of man, and selection in relation to sex. Evolution; Heredity; Human beings; Natural selection. CHAP. XII.) FISHES. 353 Salmo lycaodon of the change, as Mr. J. K. Lord^ believes, is permanent, and best marked in the older males which have previously ascended the rivers. In these old males the jaw becomes developed into an immense hook-like projection, and the teeth grow into regular fangs, often more than half an inch in length. With the European salmon, ac- cording to Mr. Lloyd,'-^ the temporary hook-like structure serves to strengthen and protect the jaws, when o
. The descent of man, and selection in relation to sex. Evolution; Heredity; Human beings; Natural selection. CHAP. XII.) FISHES. 353 Salmo lycaodon of the change, as Mr. J. K. Lord^ believes, is permanent, and best marked in the older males which have previously ascended the rivers. In these old males the jaw becomes developed into an immense hook-like projection, and the teeth grow into regular fangs, often more than half an inch in length. With the European salmon, ac- cording to Mr. Lloyd,'-^ the temporary hook-like structure serves to strengthen and protect the jaws, when one male. Pig. 28.—Head of female salmon, charges another with wonderful violence; but the greatly de- veloped teeth of the male American salmon may be compared with the tusks of many male mammals, and they indicate an offensive rather than a protective purpose. The salmon is not the only fish in which the teeth differ in the two sexes ; as this is the case with many rays. In the thornback {Rata clavaf) the adult male has sharp-pointed teeth, directed backward, while those of the female are broad • "The Naturalist in Vancouver's Isl- » "Scandinavian Adventures," voL \, and," vol. i. 1866, p. 54. 1854, pp. loo, 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 Hurst
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