. Animal biology. Zoology; Biology. £xcretory Testes Progr/oit/'c^ Fig. 78.—The beef tapeworm, Taenia saginata (Goeze). A, the whole tapeworm, with many portions omitted, to illustrate the change in the form of segments in different parts of the body. {From Leuckart, "Parasiten des ;) X ^2. ^' scolex and neck in an extended condition. The rostellum bears no hooks and the tapeworm is spoken of as unarmed. {From Leuckart.) X 5. C, proglottid, showing the sex organs. {Also from Leuckart.) X 7. D, ripe proglottid, showing the uterus distended with eggs. X 13^. disappearance of t
. Animal biology. Zoology; Biology. £xcretory Testes Progr/oit/'c^ Fig. 78.—The beef tapeworm, Taenia saginata (Goeze). A, the whole tapeworm, with many portions omitted, to illustrate the change in the form of segments in different parts of the body. {From Leuckart, "Parasiten des ;) X ^2. ^' scolex and neck in an extended condition. The rostellum bears no hooks and the tapeworm is spoken of as unarmed. {From Leuckart.) X 5. C, proglottid, showing the sex organs. {Also from Leuckart.) X 7. D, ripe proglottid, showing the uterus distended with eggs. X 13^. disappearance of the Posfe//u/rf ?Hooks -Sucker. Fig. 79.—Scolex of the pork tapeworm, Taenia solium, Linnaeus. {From Leuckart, "Parasiten des ;) X 30. Shows a rostellum with hooks, this being an armed tapeworm. The illustra- tion is not artistically cor- rect, in that the suckers on the two sides are not shown in true perspective. They should be shown in exact side view. duction of proglottids digestive system and the absence of the processes of ingestion, digestion, and egestion, all of the other processes in metabolism still remain. Absorption occurs over the surface of the body; circulation is from cell to cell; assimilation and dissimilation, secretion, excretion, and elimination are still carried on in the same manner as in the nonparasitic forms. Anal openings have been described in some trematodes and openings from the branches of the gastrovascular cavity to the outside in turbellarians, but the extent to which these can function in egestion is not known. 196. Reproduction.—Reproduction in this phylum occurs both sexually and asexually. Sexual reproduction is, however, the more usual type. Asexual reproduction in a planarian is usually by transverse fission, but a type of fragmentation has also been described in which the body breaks up into a number of fragments each of which by a process analogous to regenera- tion becomes a complete individual. The pro- is a
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