VARIOUS FORMS OF TAPEWORMS. 



53 



proUgerous vesicles, and they may break away and float in the 

 fluid contents of the cyst. 



Secondly, there are formed in the hydatid membrane (ct) 

 cavities {vf), which gradually become larger and pass either in- 

 ternally (vf") or externally {vf) ; these are secondary or daughter- 

 vesicles. As a rule, we do not find internal and external 

 daughter- vesicles in the same hydatid. These secondary or 



Pig. 15.— Diagram showing formation of Peoligerous and Secondahy 

 Vesicles in Echinococous. Railliet. 



ct, Hydatid membrane ; m, germinal vesicle ; vp, proligerous vesicles ; vf, daughter- 

 vesicle commencing to form ; vf, daughter-vesicle passing externally ; vf", daughter- 

 vesicle passing internally ; vfi, internal daughter - vesicle ; vfe, external daughter- 

 vesicle ; vpfi, internal grand-daughter-vesicle ; vpfe, external grand-daugbter-vesicle. 

 (From Par. Dis. Ani., Neumann.) 



daughter-vesicles may produce proligerous vesicles, and thus 

 scolices, internally (vfe). Some do not produce scoHces but 

 other vesicles, grand-daughter-vesicles {vpfi and vpfe). These 

 grand -daughter- vesicles may again form internal proligerous 

 vesicles, and thus scolices ; or they may remain as acephalocysts, 

 just as the primary proligerous vesicle does occasionally. 



O will thus be seen that one ovum of Tcenia echinococcus may 



