GENUS HYMENOLEPIS 59 



C. Order Cyclophyllidea 



Scolex with four cup or saucer-shaped suckers and in the 

 center an apical organ or rostellum of varied form; no 

 uterine pore; vitellaria compact, single near posterior end 

 of proglottid; proglottids set free after maturity; eggs thin 

 shelled with no operculum, contain onchosphere with one 

 or more membranes. 



General discussion. The order Cyclophyllidea contains 

 most of the human tapeworms. Of this group Hymenolepis 

 nana, H. diminuta, Taenia solium, T. saginata and Echino- 

 coccus granulosus (T. echinococcus) are of sufficient impor- 

 tance to be described more fully. Other forms which are 

 incidental in man or insufficiently knawn are Dipylidium 

 caninum, a common dog tapeworm. Hymenolepis lanceolata, 

 Davainea madagascariensis, Davainea asiatica, Taenia afri- 

 cana, Taenia hominis, T. confusa, and T. bremneri. It is 

 doubtful if all the forms reported from man belonging to the 

 genus Taenia are distinct species; they may simply represent 

 abnormalities of one of the two common species. 



1. Genus Hymenolepis. Small worms; proglottids always 

 broader than long; three large testes in each proglottid; 

 genital pores unilateral, uterus persistent, sac-like; eggs 

 round or oval with two or three distinct envelopes. 



H. nana H. diminuta 



Length 10 to 45 mm. Length 20 to 60 cm. 



Width 0.5 to 0.7 mm. Width up to 3.5 mm. 



Scolex globular 0.25 to 0.30 mm. Scolex 0.2 to 0.5 mm. in diame- 



in diameter ter 



Rostellum with a single circlet Rostellum rudimentary and 



of 24 to 30 hooks, 14^ to 18/z unarmed 



in length 



Proglottis up to two hundred Proglottis 600-1000 



in number 



Infection direct without inter- Larval stage a small cysticercoid 



mediate hosts found in insects 



