60 



VARIOUS FORMS OF TAPEWORMS. 



proUijrrous vvsic/es; and they may break away and float in the 

 fluid contents of the cyst. 



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

 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 

 daughter-vesicles may produce proligerous vesicles, and thus 

 soolices, internally {vfe). Some do not produce scolices but 

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



Fig. 18.— T/knia serrata (nat size). (From Par. Uis. Ani., Xenniann.) 



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 occasionaJlj'. 



It will thus be seen that one ovum of Tuniia crliinococcus may 

 produce hundreds of scolices, future tapoworms, should a dog 

 devour the organs sull'ering from this echinococcosis. 



Lastly, there is a form of Echinococcus known as a muUi- 

 lonilar form, in which the vesicles remain very small, whereas 

 in the others they may assume an immense size. These vesicles 

 remain attached together, and may produce a huge mass eight 

 or nine inches across, united together by connective tissue. 



