1. Frogs were collected from a single area in the West Riding of Yorkshire and examined for adult helminth parasites. The following species were found: Polystoma integerrimum, Gorgoderina vitelliloba, Haplometra cylindracea, Dolichosaccus rastellus, Rhabdias bufonis, Cosmocerca ornata, Oswaldocruzia filiformis, Aplectana acuminata and Acanthocephalus ranae.2. The seasonal incidence and intensity of infection was studied by monthly examinations of 2413 frogs over a period of 4 years. The highest incidence of parasitization by helminths occurred in the autumn. In general, when the incidence was high, the intensity of infection was also high.3. The incidence of infection was generally higher in male than in female frogs. This effect of the host's sex was much more marked immediately before the breeding season than at any other time of the year.4. Possible reasons for these variations in levels of infection are discussed.
1. P.silusiae is shown to be unable to resist desiccation on a microscope slide for periods above half an hour, although larvae within the uterus of the mother can survive for somewhat longer periods.2. When “protected” by a colloidal gel, the worms are shown to resist desiccation for several months. Such “protected” worms are more resistant to temperature extremes than “non-protected” ones.8. P. silusiae is immobilized in glucose solutions above 1M strength, although it can resume mobility on dilution of the solution, even after fourteen days in 4 M glucose solution.4. P. silusiae is shown to be positively chemotactic towards oxygen, in addition the gravid females are negatively geotactic.5. Drosophila fimcbr is is shown to act as a dispersal agent for P. silusiae.
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