LIFE HISTOEY OF THE LIVER-FLUKE. 101 



cercariae had the habit of throvvino; off their tails and cravvlina: 

 about by the aid of their suckers, and he thought that the 

 larvee of the liver-fluke might encyst upon plants. Kiichen- 

 meister had suggested certain slugs as possible hosts of 

 Fasciola hepatica. On April 7th, 1880, the 'Times' 

 published a letter written by Dr. Cobbold to contradict the 

 statements made by Dr. J. Harley, who denied the existence 

 of any intermediate host. The letter contained the followino- 

 sentence: — '* The investigations of the lamented Willemoes- 

 Suhm render it almost certain that Cercaria cystophora 

 infesting Planorbis marginatais the higher larval state of 

 the small fluke (Distoma lanceolatuin), and the still later 

 researches of Leuckart point to the mollusc called Lymnsea 

 truncatula as the bearer of the cercarian stage of Fasciola 

 hepatica." Seven days later, on April 14th, 1880, the late 

 Dr. RoUeston gave, in a letter to the ' Times,' reasons for 

 regardiug the black slug, Arion ater, as the intermediate host 

 of Fasciola. Since that time Ercolani^ has made a similar 

 suggestion for certain terrestrial molluscs. He found that larval 

 trematodes were of far more frequent occurrence in land- 

 molluscs than had hitherto been supposed, and this circum- 

 stance, together with the failure of the most illustrious hel- 

 minthologists to discover the genesis of F. hepatica, led him 

 to think that it was in this direction that success would even- 

 tually be obtained. 



On the 2nd of the following June the Royal Agricultural 

 Society of England offered Dr. Rolleston a grant for an inves- 

 tigation into the life-history of the liver-fluke. Dr. Rolleston 

 being unable himself to undertake the work, mentioned my 

 name to the Society, and the research was begun by me on 

 June 7th. 



On Dec, 22nd, 1880, I found in a Limnaeus truncatulus, 

 captured on an infected field at Wytham, near Oxford, on the 

 24th Sept., and since that time kept in an aquarium in the 



^ "Deir Adattamento delle specie all' ambiente," ' Meniorie dell' Accademia 

 delle Scienze dell' Istituto di Bologua,' serie iv, tomo ii, 1881, pp. 24.1, 327. 



