ABSTRACT
Biomphalaria Alexandrina snails were collected from five different localities, and their progenies through successive generations, were compared with respect to their susceptibility to infection with the local strain of Schistosoma mansoni. There was difference in the susceptibility between snails from different localities and this susceptibility increased through the successive generations. Progenies from negative parents were less susceptible and the resistance increased through negative generation whereas those from positive parents were more susceptible and the susceptibility increased through the positive generations. Results from studying the inheritance of susceptibility among progenies, produced individually from the same snail demonstrated some snails with great diversity of genetic pattern of susceptibility among progenies. Some snails presented with progenies testing 0% susceptibility and others with progenies testing 100% susceptibility. These snails could be the beginning of true breeding refractory or susceptible stocks. Field snails and their progenies have been reared individually to reproduce only with self-fertilization. Several morphologidal differences in pigmentation have appeared which would be useful in the genetic studies on B. Alexandrina