Outlines of zoology . id CRA YFISH. 293 and becomes thicker in its passage through the genitalducts. It is possible that the genital ducts representmodified nephridia, and that the cavities of the gonadsare coelpmic. • The ovaries are like the testes, but more compact. Theeggs are liberated into the cavity of the organ, and pass outby short thick oviducts opening on the second pair ofwalking legs. As they are laid they seem to be coated withthe secretion of the cement glands of the abdomen, and themother keeps her tail bent till the eggs are glued to thesmall Fig. 146.—Female repr
Outlines of zoology . id CRA YFISH. 293 and becomes thicker in its passage through the genitalducts. It is possible that the genital ducts representmodified nephridia, and that the cavities of the gonadsare coelpmic. • The ovaries are like the testes, but more compact. Theeggs are liberated into the cavity of the organ, and pass outby short thick oviducts opening on the second pair ofwalking legs. As they are laid they seem to be coated withthe secretion of the cement glands of the abdomen, and themother keeps her tail bent till the eggs are glued to thesmall Fig. 146.—Female reproductive organs of crayfish.—After Suckow. Ovaries ; , fused posterior part; od.^ oviduct; vu.^ femaleaperture on the second walking leg. Before this, however, sexual union has occurred. Themate seizes the female with his great claws, throws her onher back, and deposits the seminal fluid on the ventralsurface of the abdomen. The fluid flows down the canalformed by his first abdominal appendages, and these seemto be kept clear by the movements of the next pair, whichare also modified. On the abdomen of the female theagglutinated spermatozoa doubtless remain until the eggsare laid, when fertilisation, in the strict sense is achieved. The Development has been very fully worked out, and is of interestin being direct, without the metamorphosis so common among tha 294 PHYLUM ARTHROPODA. Arthropoda. The spherical ovum is surrounded by a cuticular vitellinemembrane, and contains a considerable quantity of yolk. After ferti-lisation the segmentation nucleus
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Keywords: ., bookcentury1900, bookdecade1910, bookidcu3192, booksubjectzoology
