Elementary text-book of zoology, general Elementary text-book of zoology, general part and special part: protozoa to insecta elementarytextbo00clau Year: 1892 Fig. 2GG.—Ripe proglottides ready to separate. a, of Trcnia solium ; h, of Teenia mediocanellata ; Wc, water-vascu'ar (excretory) canal. genitcal cloaca, which lies either on the ventral surface of the segment {Bothriocejxdus), o^ on the lateral margin {Tcenia) (fig. 2G5). In the last case it is placed alter- nately on the right and on the left side. Nevertheless it may happen that the two genital openings are widely separate, the male
Elementary text-book of zoology, general Elementary text-book of zoology, general part and special part: protozoa to insecta elementarytextbo00clau Year: 1892 Fig. 2GG.—Ripe proglottides ready to separate. a, of Trcnia solium ; h, of Teenia mediocanellata ; Wc, water-vascu'ar (excretory) canal. genitcal cloaca, which lies either on the ventral surface of the segment {Bothriocejxdus), o^ on the lateral margin {Tcenia) (fig. 2G5). In the last case it is placed alter- nately on the right and on the left side. Nevertheless it may happen that the two genital openings are widely separate, the male opening being placed at the side, the female on the surface of the segment. As the segments increase in size and become further removed from the head, the contained generative organs gradually i-each matuiity in such a way that the male generative oi'gans arrive at maturity n\ther earlier than the female. As soon as the male elements are mature, copulation takes place, and the receptaculum seminis is filled with sperm, and then only do the female generative organs reach maturity. The ova are fertilized and pass into the uterus, which then assumes its characteristic form and size. As the uterus becomes distended, the testes and then the ovaries and vitellaria are more or less completely absorbed (fig, 266), The posterior proglot- tides, viz,, those which are ready for separation, have alone under- gone full development, and the eggs in their uterus often contain completely developed embryos. Accordingly we can recognize in a continuous series of the seg- ments the course of development passed through by the sexual organs and products in their origin and gradual progress towards maturity. The number of sesrments between that with the first trace of the eenerative organs
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