365 



ON POLYCERCUS : A PROLIFERATING CYSTIC 

 PARASITE OF THE EARTHWORMS. 



By William A. Haswell, M.A., D.Sc, Challis Professor 



OF Biology, and J. P. Hill, F.L.S., Demonstrator 



OF Biology, University op Sydney. 



(Plates xix.-xx.) 



The name Polycercus was proposed in 1883 by Villof^ for a 

 remarkable cystic worm described in 1868 by Mecznikoff.f The 

 parasite in question was discovered by the latter at Odessa in 

 specimens of Lumhricus terrestris, and does not seem to have 

 been re-investigated since, the accounts of it and the comments on 

 its affinities given by Moniez,| Leuckart,§ and Villot being all 

 based on Mecznikoff's observations and figures. 



A form exhibiting unmistakable affinities with Mecznikoff's 

 has been found by us in a considerable proportion of specimens of 

 an earthworm ( Didymogaster sylvatica, Fletcher) common under 

 stones and dead timber in certain parts of New South Wales ; and 

 an investigation of its structure and development has revealed 

 features of some importance, which, so far as we have been 

 enabled to ascertain, have not been previously noticed. 



* " Memoire sur les cystiques des T^nias." Ann. des Sci. Nat. Zool. 

 6me s6rie, Tome xv. (1883). 



t Verhandlungen der Petersburger Naturf. Versammlung, Zool. pp. 263- 

 266. 



:|: " Essai Monographique sur les Cysticerques. " Trav. de ITnst. Zool. 

 de Lille, Tome iii. (1880). I have to thank Professor Giard for his kindness 

 in sending me a copy of this work, as well as one of the *' Recherches sur 

 les T^nias" by the same author. — W.A.H. 



§ "Die Menschlichen Parasiten." 



I 



