78 A FURTHER KNOWLEDGE OF THE CYSTIC CESTODES, 



bud which arises from its floor, thus confirming Hoek's* view that 

 " Der Scolex ensteht dan bei Tetrarhynchus auf dem Boden dieser 

 Einstiilpung aus knopfformiger Anlage," and also Wagener as 

 quoted by Leuckartf — " If we imagine the thimble-like projection 

 from the base of the sac broadened out above like a mushroom, 

 we have the head of a Dibothrium, which might become a 'dibo- 

 thrian ' Tetrarhynchus by the addition of proboscides." 



Leuckartjj on the other hand, considers "that it is the sac-like 

 invagination of the bladder itself which produces the head. The 

 elevation always appears only as a secondary structure of subordi- 

 nate morphological importance, and is, moreover, by no means so 

 widely distributed as the statements of some investigators would 

 lead one to suppose." He bases this view on an examination of 

 young Tetrarhynchus bladders from Lophius piscatorius, in which 

 he finds, "that the elevation only takes place at a time when the 

 suctorial cups and proboscides are already formed and when the 

 head, with its different parts, is thus essentially mature." If this 

 be so in the case he examined, then we must admit that in the 

 Tetrarhynchidce, as among the Tceniadce, the head may arise in 

 two distinct ways. It may arise directly from the invagination 

 sac or it may arise as a bud from the bottom of the invagination 

 sac. The occurrence of the latter of these two methods is denied 

 by Leuckart, but Moniez,§ from the examination of Cysticercus 

 pisi/ormis, is convinced "que la tete dii Cysticerque bourgeonne 

 au fond de I'iuvagination comme I'avait indique Wagener," and 

 Hamann|| has also described and figured (cf. especially his fig. 5, 

 taf. I.), in the development of the Cysticercoid of Tcenia sinuosa 

 from Gammarus pulex, a plug-shaped structure which arises by 



* " Ueber den encystirten Scolex von Tetrarhynchus," Niederlandisches 

 Archiv fiir Zoologie, B. v. p. 3. 



t Loc. cit. p. 374. 



t Loc. cit. p. 375. 



§ "Essai Monographique sur les Cysticerques," p. 36 



II " In Gammarus pulex lebende Cysticerkoiden mit Schwanzanhangen," 

 Jenaische Zeitschrift, Bd. xxiv. p. 2-3, taf. i. figs. 4-8. 



