JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. This content downloaded from 130.102.42.98 on Mon, SUMMARY(1) Bulinus globosus populations were sampled weekly in two reservoirs over 2 years, using plastic sheet snail traps and mark recapture techniques to measure density, growth rates and reproduction.(2) Captive cohorts were raised in netted boxes in the reservoirs to measure age specific reproduction and egg viability.(3) Growth rates were used to identify snail cohorts, and life tables were constructed to measure mortality rates and the intrinsic rate of natural increase (rm).(4) Values for ri were inversely related to mean water temperatures, with no positive values when the mean water temperature exceeded 28-5 'C during a cohort's early reproductive phase.(5) Rainfall (and associated environmental variables) appear to influence the carrying capacity of the snail habitat, so that in both reservoirs, populations increased fastest and to the highest densities when large amounts of unseasonal rain fell during the coolest months.

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