BY J. P. HILL. 69 



Superficially there is a slight similarity between an isolated Echi- 

 nococcus head and, say, the Cysticercus from Liali=!, but detailed 

 comparison shows they have little in common. Leuckart,* after 

 referring to the similarity in disposition between the enclosing 

 portion of the Echinococcus-heAcX and the caudal bladder of a 

 Cysticercus, says: — "Nevertheless it is impossible to regard the 

 capsular envelope of the retracted Echinococcus-he-dd as a caudal 

 bladder, and that not only because it forms an integral part of 

 the head, and is included in the body of the future tapeworm, but 

 more especially because of its entirely different origin." In the 

 foregoing we have considered the part in which the head is 

 invaginated in these forms as representing the caudal vesicle and 

 body, and that it does not become part of the future tapeworm, 

 Von Linstow'sf observation of the commencement of segmentation 

 in the part immediately succeeding the head in Cysticercus (Pies- 

 tocystis) Dlthyridium strikingly bears out. 



Multiplication in the genus Piestocystis takes place, according 

 to Diesing, by a process of external proliferation from the caudal 

 vesicle. This method of multiplication certainly does not hold 

 good for the forms under consideration, and Villot;}: agrees with 

 Leuckart § in believing that the so-called buds are malformations 

 due to purely mechanical causes ; still it is possible that certain 

 species do multiply by external proliferation. In the two forms 

 under consideration internal proliferation undoubtedly takes place, 

 in the first one Cysticercus only is formed, in the second three 

 may be thus formed. Here the caudal vesicle does not proceed 

 from the proscolex by simple growth and modification of structure 

 as in Villot's genus Cysticercus, but it represents a secondarily 

 formed structure derived by internal proliferation from the pro- 

 scolex, which remains persistent in the form fjora Hoplocephalus 

 as the inner lining of the cyst cavity, and in the form from Lialis 



* Loc. cit. p. 604. 

 t " Neue Beobachtungen au Helminthen," Archiv f. Naturgesch. , B. i. 

 1878, p. 222. 



X Loc. cit. p. 22. 

 § Loc. cit. p. 356. 



