Elementary text-book of zoology (1884) Elementary text-book of zoology elementarytextbo0101clau Year: 1884 104 ORGANIZATION AND DEVELOPMENT OF ANIMALS IN GENERAL. the offspring may be discharged by the male, , Alytes and the Lophobranchia. Male birds also often share with the female the labour of building the nest, of bringing up and protecting the young. But it is a rare exception to find, as in Cottus and the Stickleback (Gasterosteus), that the care and protection of the young fall exclusively upon the male, that he only bears the brood pouch and alone builds the nest,—an exception whi
Elementary text-book of zoology (1884) Elementary text-book of zoology elementarytextbo0101clau Year: 1884 104 ORGANIZATION AND DEVELOPMENT OF ANIMALS IN GENERAL. the offspring may be discharged by the male, , Alytes and the Lophobranchia. Male birds also often share with the female the labour of building the nest, of bringing up and protecting the young. But it is a rare exception to find, as in Cottus and the Stickleback (Gasterosteus), that the care and protection of the young fall exclusively upon the male, that he only bears the brood pouch and alone builds the nest,—an exception which bears strong witness to the fact that the sexual differences both in form and function were first acquired by adaptation. In extreme cases, the sexual dimorphism may lead to so great a difference in the sexes that without a knowledge of their development Sp a FIG. 98.— Chondracanthus gibbosus, magnified about 6 times, a, female from the side. 6, female from the ventral surface with the male (F) attached, c, male isolated, under strong magnification. An', anterior antenna ; An', clasping antennas; F' and F', the two pairs of feet; A, eye ; OD, egg sacs ; Oe, oesophagus ; D, intestine ; M, mouth parts ; T, testis ; Vd, vas deferens ; Sp, spermatophore. and sexual relations, the one sex would be placed in a different family and genus to the other. Such extremes are found in the Rotifera and parasitic Copepoda (Chondracanthus, Lernreopoda, fig. 98, «, b, c), and are to be explained as the result of a parasitic mode of life. The difference in the two kinds of individuals representing and maintaining the species, whose copulation and mutual action was known long before it was possible to give a correct account of the roal nature of reproduction, has led to the designation ' sexes,' from which tho term sexual has been taken to apply to the organs and manner of reproduction.
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