Succinea putris has often been reported to be the host of the asexual part of the cycle of the parasitic trematode Leucochloridium paradoxum. A central sporocyst mass gives rise to rod-like processes (sacs) which contain from 100 to 200 metacercariae. The sporocyst causes great damage to reproductive and other organs of the intermediate host. The tips of two sporocyst sacs can enter into the optic tentacles, often pulsating under the influence of light. The sporocyst sac possesses either brown or green rings, both of which varieties have been found in the Netherlands. For a more extensive treatment of this subject the reader is referred to ZELLER (1874), WESENBERGLUND (1931), VAN BENTHEM JUTTING (1933), VENMANS (1951), HONER (1960) and SCHMIDT (1964). Infected specimens have not been found often in the Netherlands. Up to 1951, 16 infected animals had been reported (VENMANS). Some of these were specimens of S. pfeifferi, now known as S. elegans (VAN REGTEREN ALTENA, 1959) Thus both S. elegans and S. putris can be infected by this trematode. Since VENMANS’ publication appeared, only a few other reports about observations of the parasite have appeared. Recently BUTOT (1966) reported that MEIJER found a specimen of S. putris infected with a parasite of the brown-ringed variety.