TARIOUS FORMS OF TAPEWORMS. 



53 



proligermis 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 (?/), wliich gradually become larger and pass either in- 

 ternally ((of) or externally (/;/'') ; 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 



Fig. 15. — Diagram showing formation of Pp.oligerous and Secondary 

 Vesicles in Echinococcus. Railliet. 



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

 vesicle commencing to form ; vf, daughter-vesicle passing externally ; vf'\ daugliLer- 

 vesiole passing internally ; vjl, internal daughter • vesicle ; vfn, external daughter- 

 vesicle ; vpjl, internal grand-daughter-vesicle ; vpfe, external grand-daughter -vesicle. 

 (From Par Dls. Ani., Neumann.) 



daughter-vesicles may produce proligerous vesicles, and thus 

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

 other vesicles, grand-daughter-vesicles {v-pfi 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. 



It will thus be seen that one ovum of Tcsnia echinococcvs may 



