. A manual of zoology. Zoology. III. CESTODA 249 When a circle of hooks is present it is on the anterior end and is moved by a special apparatus, the roslellum, a plug of complexly arranged muscles (fig. 226) which can arch and flatten the central area. Each hook has its fjoint outwards and its base with two roots, one of which rests on the rostellum; the protrusion of the rostellum forces the points outwards into the mucous membrane of tlie intestine. In some Ta-nia; without hooks (T. saginata) the rostellum is replaced by a sucker-like depression. Since the rostellum arises in development fr
. A manual of zoology. Zoology. III. CESTODA 249 When a circle of hooks is present it is on the anterior end and is moved by a special apparatus, the roslellum, a plug of complexly arranged muscles (fig. 226) which can arch and flatten the central area. Each hook has its fjoint outwards and its base with two roots, one of which rests on the rostellum; the protrusion of the rostellum forces the points outwards into the mucous membrane of tlie intestine. In some Ta-nia; without hooks (T. saginata) the rostellum is replaced by a sucker-like depression. Since the rostellum arises in development from a similar cup, it may be a modified apical sucker, but it is doubtful how far com- parisons may be made with the oral sucker of the trematodes. The animals are almost always hermaphroditic and the gonads are ec|ual in numbers to the proglottids, so that these were formerly regarded as sexual individuals of a colony, each with its own reproductive apparatus. Two types must be recognized. In the one the presence of vitellaria and the separate openings of uterus and vagina recall the conditions in trema- todes, while in the second the uterus ends blindly and the vitellaria are modilied into a small albumen gland. Since vagina and vas deferens almost always open together, self-impregnation is possible, but cross- fertilization of separate proglottids has been seen. The general features of the two types may be made out from figures 227 and 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 Hertwig, Richard, 1850-1937; Kingsley, J. S. (John Sterling), 1854-1929, ed. and tr. New York, H. Holt
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectzoology, bookyear1912
