70 A FURTHER KNOWLEDGE OF THE CYSTIC CESTODES, 



as the inner lining of the cyst cavity together with the cellular 

 network in the interior of the cyst. 



The two forms under consideration are thus brought into close 

 relationship with certain forms included in Villot's second group, 

 but they agree so closely with one another and differ so widely in 

 other respects from the Cysticercoids that it seems advisable to 

 associate them together in Diesing's old genus Piestocystis. 



Leuckart* regards these parenchymatous forms as in many ways 

 connecting the Cysticercoids with the ordinary bladder worms, 

 and this is the view we here adopt. In their general structure 

 they are certainly more nearly related to the Cysticerci properly 

 so-called than to the Cysticercoids, while at the same time the 

 presence of the surrounding blastogen is a character they share in 

 common with certain of the latter. 



Finally, then, we hold the genus Piestocystis to include unarmed 

 forms, intermediate between the Cysticerci properly so-called and 

 the Cysticercoids; and \vhich are produced, one or more in number, 

 by proliferation of the blastogen (proscolex). 



The Lialis Cysticercus may be termed Piestocystis Lialis, and 

 the Hoplocephalus Cysticercus Piestocystis Hoplocephali. 



PART II. 



On a Monocercus from Didymogaster. 



While examining specimens of the earthworm Didymogaster 

 sylvatica, Fl., for the Polycercus described by Prof. Haswell and 

 myself in a previous part of these Proceedings,! one individual 

 was found to be infected by a Cysticercoid belonging to the allied 

 genus Monocercus, for which I propose the name of Monocercus 

 Didymogastris. The generic name Monocercus was proposed by 

 Villot:}: for cystic forms of the type of Cysticercus arionis, in 



* Loc. cit. p. 655. 

 t P.L.S.N.S.W. Vol. viii. p. 365. 

 t " M^tnoire sur les Cystiques des T^nias," Ann. des Sci. Nat. (6), T. xv. 

 1883, p. 35. 



