. A manual of zoology. Zoology. ROTIFERA 259 8. The Cestoda have no digestive tract; scolex and proglottids are usually developed. 9. The scolex is the organ of attachment, and as such is pro\"ided with suckers and frequently with hooks. It also produces the proglottids by terminal budding. 10. The proglottids contain an hermaphroditic sexual apparatus. 11. The eggs produce a six-hooked emljryo which must pass into an intermediate host, either by taldng the eggs mth the food, or the embryo must pass into the water, where it infects fishes. 12. The emliryo, in the intermediate host, become
. A manual of zoology. Zoology. ROTIFERA 259 8. The Cestoda have no digestive tract; scolex and proglottids are usually developed. 9. The scolex is the organ of attachment, and as such is pro\"ided with suckers and frequently with hooks. It also produces the proglottids by terminal budding. 10. The proglottids contain an hermaphroditic sexual apparatus. 11. The eggs produce a six-hooked emljryo which must pass into an intermediate host, either by taldng the eggs mth the food, or the embryo must pass into the water, where it infects fishes. 12. The emliryo, in the intermediate host, becomes encysted and changes directly to a scolex (pleurocercoid) or into a bladder worm (cysticercus) which prcduces internally one or more scolices. 13. The scolex is freed from its cyst when taken into the stomach of the proper host, and then can develop into a tapeworm. 14. In man occur as cysticerci Tania echinococcus (adult in dog) and T. solium; as adults Tania solium (cysticercus in pigs), T. saginala (cysti- cercus in cattle), and BolJrriocepIialus latus (pleurocercoid in fish). 15. The Nemeetini have a complete alimentary canal with anus, blood-vessels and a proboscis dorsal to the digestive tract. PHYLUM V. ROTIFERA (ROTATORIA). The aquatic rotifers or wheel animalcules are among the smallest Metazoa, and can be distinguished from the Infusoria, which they resemble in habits, only by the microscope. The body is divisible into three regions, head, trunk, and tail. The trunk is covered by a tough cuticle into which head and tail can. Ij m Fig. 238.—Diagram of rotifer (after Delage et Herouard). 6, brain; /?', pulsating vesicle of excretory system; 5, stomach. be retracted. The tail or 'foot' is often composed of rings which can be tele- scoped into each other. The last tail ring often bears a pair of pincer-like stylets by which, together with adhesive glands, the animal adheres to objects. The head is expanded in front to a trochal disc, an apparatus of varying shape, sur
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