200 PLATHELMINTHES 



rostellum retractile and with or without hooks; 3 testes in each seg- 

 ment; with a sac-like uterus filling the ripe segment: about 30 species; in 

 mammals and birds. 



H. nana (von Siebold). The dwarf tapeworm (Fig. 326). Length 

 15 mm. or more; breadth .7 mm.; scolex with a single row of about 28 

 hooks: in the small intestine of man and the rat and 

 mouse; the cysticercoid lives in the intestinal villi of the 

 same host; the parasite often causes diarrhea and nervous 

 attacks. 



H. carioca (Magalhaes). Length up to 8 cm.; width 

 .7 mm.; rostellum without hooks; edge of strobila serrate: 

 in chickens; common. 



H. dimnuta (Rudolphi). Length up to 6 cm.; width 

 4 nun.; rostellum rudimentary, without hooks: in cats and 

 mice. 



Family 3. DAVAINEIDAE. 



Scolex with hooks on a retractile rostellum and 



Fig. 326 numerous small hooks in the suckers; genital pore usually 



nana ^^1 Only One side of a segment: 3 genera; in mammals and 



(Leuckart). -^ o & 7 



birds. 

 Davainea Blanchard and Railliet. Small worms; eggs in capsules 

 in the middle area of the ripe segment: about 15 species. 



D. salmoni Stiles. Length 88 mm.; breadth 3 mm.; number of seg- 

 ments about 450 ; genital pores generally alternate : in Lepus sylvaticus and 

 L. melanotis. 



Family 4. T^NIIDAE. 



Scolex usually with a rostellum with hooks; uterus, in the ripe seg- 

 ment, composed of a median tube and lateral branches; usually long 

 worms with segments longer than wide; genital pores alternating irregu- 

 larly and never on both sides of a segment : several genera. 



1. T^ffiNlA L. With the characters of the family : numerous species, 

 which are usually found in predacious mammals and man, the cysticer- 

 cus being found in ruminants and other plant feeders. 



T. saginata Goeze. The beef tapeworm (Fig. 327). Length 10 m. 

 or more, with over a thousand segments, usual length 4 to 8 m. ; ter- 

 minal segments about 20 mm. long and 7 mm. broad, containing a uterus 

 which has from 20 to 30 brandies on each side; scolex 2 mm. thick, 

 without rostellum or hooks: in the human intestine; the cysticercus 

 {C. hovis) is about 9 mm. long and 5 mm. thick and lives in the muscles of 

 cattle, and a person may infect himself with the worm by eating rare 

 beef; the commonest human tapeworm in this country. 



