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; /<-, flame cell; 

 gg, gastric gland; i, intestine; m, masta.x; ov, ovary; pg, pedal gland ; />?', 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, 

 surrounded by a ring of cilia of use in swimming and in directing food to the 

 ventral mouth. The alimentary canal consists of oesophagus, masta.x (chewing 



