Dr. P. dc Pilippi on the Larv<R of the Trematode Worms, 129 



XIII, — Observations on the Larvee of the Trematode Worms. 

 By Dr. P. de Filippi*. 



Having this summer pmsued my investigations upon the Tre- 

 matode worms in the hirva state, I have succeeded in finding 

 some new forms, and in adding to the results of my previous 

 observations some details as to the mode of life of these crea- 

 tures. 



The Palndina imjmra, of which I have captured many indivi- 

 duals in different localities in the vicinity of Turin, has furnished 

 me with three new species of these i)arasites : — 



1. Some Redice producing Cercarise of Distonium, very di- 

 stinctly characterized by a tubercular body, and by the small 

 ventral disk situated at the posterior third of the body, but 

 especially by the bifurcate excretory organ, forming two large, 

 lateral, twisted vessels, which ascend to the sides of the anterior 

 sucking-disk. This species becomes encysted with the greatest 

 facility, even on the stage of the microscope. It has shown me 

 that in the formation of the cyst, after the concentric layers of 

 mucosity exuded by the Cercaria, the skin of the latter assists, 

 becoming detached, and forming the inner wall of the cyst 

 itself. 



2. A very fine Cercaria of Monostomum, furnished with large 

 eyes in the form of two semi-lunar spots, with a tolerably strong 

 pharyngeal bulb, and with a tail provided with a membranous 

 crest. This species is produced from a very elongated Kedia, 

 without lateral appendages. 



3. Some very peculiar nurses, almost identical in their or- 

 ganization, vital properties, and the form of the Cercarise pro- 

 duced by them, with those found by M. Moulinie in the 

 Limaces-\. This is decidedly a third kind of nurse, very different 

 from the two known up to this time, and for which I have re- 

 served the names of Sporocystis and Redia. They present the 

 form of a cylindrical sheath, wath pretty thick walls, of which 

 the narrowed anterior extremity forms a button or a head. This 

 sheath is contractile; the head especially moves, and elon- 

 gates and shortens itself, issuing from and re-entering a sort of 

 collar. Notwithstanding this vitality which they enjoy, these 

 sheaths did not present any vessels or intestines, or even a 

 mouth. The cavity of the body is filled with Cercarise, which, 

 like those described and figured by M. Moulinie, are charac- 

 terized by a very short tail, by a rounded excretory organ of 



* Translated by W. S. Dallas, F.L.S., from the Anuales des Sciences 

 Naturelles, 4me serie, tome vi. p. 83. 



t Memoires de I'lustitut Genevois, tome iii. 

 Ann. S^- Mag. N. Hist. Ser. 2. IW. xx. 9 



