BY J. P. HILL. 75 



Grassi and Rovelli'^ regard the outer wall as formed by the tail, 

 the part on which in the Cysticercus of Tcenia elliptica they find 

 the hooks of the embryo are borne. " In ihnen (C. arionis) ist 

 die aussere Wand, unserer Meinung nach, vorzugsweise von dem 

 Schwanze gebildet, da aich die Haken auf der ausseren Wand oder 

 auch auf dem Grenzpunkte zwisohen der ausseren Wand und 

 inneren Wand hefinden (Meissener, Leuckart, Moniez)." They 

 base their belief on the observations of Meissener, Leuckart,! and 

 Moniez, J who assert that they have seen the hooks of the embryo 

 lying on the caudal vesicle or on the body. With reference to 

 these statements, however, Villot remarks § : — " Nous sommes 

 persuade qu' on a pris pour les crochets de I'hexacanthe quelqne 

 portion des fibres elastiques, tx'es refringentes, que Ton observe 

 sous la cuticle de la v^sicule caudale." 



If we regard the so-called cyst (blastogenic vesicle) as the direct 

 derivative of the six-hooked embryo, then, as Villot further says,|| 

 " Les veritables crochets du Proscolex doivent etre cherches sur 

 le kyste." In view of these considerations, Grassi and Rovelli's 

 interpretation falls to the ground. 



Finally, it may be added that the hosts of Cysticercoids of this 

 type have now been found among the Mollusca, the Myriapoda, 

 and the Chsetopoda. 



PART III. 



On the Development of a Tetrarhynch Scolex belonging 

 TO the Genus Syxbothrium. 



The cysts on which the following account is based were taken 

 from the peritoneum surrounding the intestine of the jew-fish, 

 Scicena aquila. The form under consideration closely agrees with 



* " Embryologische Forschungen an Cestoden," Centralb. f. Bact. und 

 Parasit., Band v. 1889, p. 404. 



t Loc. cit. p. 361. 

 t Loc. cit. p. 74. 

 § Loc. cit. p. 39. 



