On the Structure and Life Histories of British Fresh-water Furcocercariae

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Abstract
Three species of furcocercariae are described. By means of direct animal experiment with secondary, intermediate and final hosts I have shown that one species develops into Tetracotyle typica Dies., the larva of Strigea tarda Steenstrup, and a connected detailed account of this life cycle is here given. Of the two other species, both of which are new, I have been able to trace the development of one into Tetracotyle n.sp. in Planorbis crista L., and P. albus Müll. Feeding experiments with this new Tetracotyle using ducklings as final hosts failed, however, to produce the corresponding adult.Effect of the parasite on the host. The usual results of helminth infection of this nature are observable, namely, marked disruption of liver tissue and in many cases complete parasitic castration of the molluscs infected.Double infection. In the course of my investigations on larval Trematodes I have met with one example of double infection with sporocysts, viz. Cercaria F.1 and F.2, within one and the same individual of Planorbis albus Müll. This condition was found only on one occasion, Cercaria F.1 being in predominance. Instances of double infection have been recorded by Faust (1971) and Sewell (1922), and from this country by Hesse (1923) and Brown (1926). The condition, however does not appear to be a common one.