. Outlines of zoology. Zoology. PROTO TRA CHE A TA. 285 each lies constricted off from its neighbours. When born the young resemble the parents except in size and colour. In P. novce zealandicc the ova pass from the ovary into the uterus in December, and the young are born in July—a long period of gestation. (b) Male (of P. edwardsii).—The male elements are produced in small testes, pass thence into two seminal vesicles, and onwards by two vasa deferentia into a long single ejaculatory duct, which opens in front of the anus. In the ejaculatory duct the spermatozoa are made into a long packet o
. Outlines of zoology. Zoology. PROTO TRA CHE A TA. 285 each lies constricted off from its neighbours. When born the young resemble the parents except in size and colour. In P. novce zealandicc the ova pass from the ovary into the uterus in December, and the young are born in July—a long period of gestation. (b) Male (of P. edwardsii).—The male elements are produced in small testes, pass thence into two seminal vesicles, and onwards by two vasa deferentia into a long single ejaculatory duct, which opens in front of the anus. In the ejaculatory duct the spermatozoa are made into a long packet or spermatophore, which is attached to the female during copulation. While it is characteristic of Arthropods, in which the develop- ment of chitin is so predominant, that ciliated epithelium is absent, it seems that in Peripatus, which is much less chitinous than the others, ciliated cells occur in some parts of the reproductive ducts, and perhaps also at the internal funnels of the nephridia. This is indeed what one would expect. Development.—There is great variety of development in different species. Thus there is much yolk in the ovum of P. novce zealandice, extremely little in that of P. capensis. In the former species the yolk has a manifold origin ; it is said to arise in the protoplasm of the ovum itself from the breaking up of the germinal vesicle, from surrounding follicle cells, and from yolk present within the ovary. In P. capensis and /'. balfouri spermatozoa reach the ovary, and there probably the ova are fertilised, but in P. nova zealandice the spermatozoa are con- fined to the receptaculum seminis, near which fertilisation seems to occur. In the maturation of the ova of P. capensis and P. balfouri two polar bodies are extruded as usual, but none have been observed in the case of P. novic. Fig. 122.—Embryos of Peripatus capensis, showing closure of blastopore and curvature of embryo.—After Korschelt and Heider. a., Anus; 61., blastophore; m., mouth ; p.
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Keywords: ., bookauthorth, bookcentury1800, bookdecade1890, booksubjectzoology
