174 



UNSEGMENTED " WORMSr 



only but many, each of which is capable of becoming an adult tapeworm. 

 The only known exception to the fact that sexual tapeworms are parasites 



Fk;. 56. — Life history of T,xUut so/unii. (After Leuckart.) 



I. Six-booked embr^'O in egg case ; 2. proscolex or bladderworni 

 stage with invaginate head ; 3, bladdenvorm with evaginated head ; 

 4. enlarged head of adult, showing suckers and hooks; 5. general 

 view of the tapeworm from small head, and thin neck to the ripe 

 joints ; 6. a ripe joint or proglottis with uterus. 



of Vertebrates, is Archigefcs sicholdii^ a simple cestode which is sexual 

 within the small fresh water worm Tuhifiw riz'uloruiii. 



