|Meixner J (1926)
Beitrag zur Morphologie und zum System der Turbellaria-Rhabdocoela: II. Ueber Typhlorhynchus nanus Laidlaw und die parasitischen Rhabdocoelen nebst Nachtragen zu den Calyptorhynchia.
Z Morphol Oekol Tiere 5:577-624.
Abstract / Notes
T. nanus, a rhabdocoel parasitic on and between the parapodia of the marine polychaete Nephthys scolopendriodes Chiaije, has been regarded as a member of the Byrsophlebidae, which differs from all other rhabdocoels in the possession of separate cf and 9 pores. Further examination of T. nanus, however, shows that it cannot be placed in this family nor in the more nearly related Anoplodiidae since the posterior pore is merely the opening of the vagina which has in T. nanus acquired a separate opening instead of joining the common atrium as in the Anoplodiidae. The anatomy of T. nanus is fully described and compared with that of Syndesmis echinorum Francois, selected as a representative of the Anoplodiidae. A newfamily.Typhlorhynchidae, erected for T. nanus, contains the one genus Typhlorhynchus Laidlaw. The nearest related family, the Anoplodiidae is contrasted and characterized. There is an extensive discussion of the probable evolution of trematodes and cestodes from rhabdocoel ancestors. Rhabdocoel parasites are limited to invertebrate hosts as are the larvae of digenetic trematodes and of cestodes. The ancestors of trematodes and cestodes were probably already specialized as to definitive hosts; this suggestion is offered as explaining the limitation of the present larvae of these groups to certain classes of invertebrates, it being supposed that the larvae still parasitize the invertebrate groups which served as hosts for the hypothetical rhabdocoelous ancestors. The further evolution of the trematodes and cestodes is linked with the differentiation of the vertebrates. A detailed discussion is given of the probable course of the differentiation of the 9 genital canal into vagina and uterus (or common duct) from the Acoela through the Turbellaria, using various Acoela as illustrations. It is concluded that the connection of the 9 duct (vagina) with the bursa is secondary. The uterus of trematodes and cestodes is regarded as homologous with the common duct or atrium of the Turbellaria, which has altered in the former groups into a long, coiled uterus as a consequence of increased egg production. The secretion of egg capsules and the glands involved in the secretion are discussed for the various groups of Turbellaria, with the conclusion that the capsules are formed by the shell glands, which are of 2 sorts[long dash]ordinary shell glands and cement glands. In the Calyptorhynchia 2 sorts of glands open into the terminal part of the 9 system, one of which is concerned in the production of the egg capsules. Koinocystis (Acrorhynchus) lacustris, Neuenburger See is new.
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