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SCIENCE

THE DESCENT OF

OF MAN

AND

SELECTION IN RELATION TO SEX

CHAPTER XII

SECONDARY SEXUAL CHARACTERS OF FISHES, AMPHIBIANS,

AND REPTILES

FISHES: Courtship and battles of the males-Larger size of the females

-Males, bright colors and ornamental appendages; other strange characters-Colors and appendages acquired by the males during the breeding season alone_Fishes with both sexes brilliantly colored Protective colors-The less conspicuous colors of the female cannot be accounted for on the principle of protection-Male fishes building nests, and taking charge of the ova and young. AMPHIBIANS: Differ. ences in structure and color between the sexes—Vocal organs. REP. TILES: Chelonians-Crocodiles—Snakes, colors in some cases protective-Lizards, battles of—Ornamental appendages-Strange differences in structure between the sexes-Colors-Sexual differences almost as great as with birds

W

E have now arrived at the great sub-kingdom of

the Vertebrata, and will commence with the low.

est class, that of Fishes. The males of Plagi. ostomous fishes (sharks, rays) and of Chimæroid fishes are provided with claspers which serve to retain the female, like the various structures possessed by many of the lower animals. Besides the claspers, the males of many rays have clusters of strong sharp spines on their heads, and several rows along “the upper outer surface of their pectoral fins.” These are present in the males of some species, which have other parts of their bodies smooth. They are only tempo. rarily developed during the breeding season; and Dr. Gün. ther suspects that they are brought into action as prehensile organs by the doubling inward and downward of the two

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