. Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote. 330 PLATTIIELMES'TIIES. genital cloaca, which lies either on the ventral surface of the segment (Bothriocepahis), O'- on the lateral margin (Tcenia) (fig. 265). 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 ge
. Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote. 330 PLATTIIELMES'TIIES. genital cloaca, which lies either on the ventral surface of the segment (Bothriocepahis), O'- on the lateral margin (Tcenia) (fig. 265). 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 reach maturity in such a way that the male generative organs arrive at maturity rather 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 FIG. 2GG.—Ripe ready to separate. a, of Txnia soliiim; b, of Ttfnia mediocanellata ; We, water-vascu'ar (excretory) canal. 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. 2G6). 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 segments between that with the first trace of the cenerative organs. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Claus, Carl, 1835-1899
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