Genetic variability and similarity were analysed in four parthenogenetic and five bisexual populations of the snail Melanoides tuberculata found in Israel. Electrophoretic studies of six enzymatic systems revealed 28 zones of activity. The average genetic identity between populations was low-0.725. A particularly low similarity (0.628) was obtained between parthenogenetic populations, compared to the average of 0.822 observed among the bisexual ones. The percentage of fixed electrophoretic bands in parthenogens was 53.9% compared to 12.5% observed in bisexual populations. The diversity of parthenogenetic populations was found to be lower than those of bisexual. The amount of electrophoretic diversity between populations of the parthenogenetic group was found to be 80%, whereas within the bisexual group the diversity between populations was only 42%.

Exposure of murine splenic B cells to insoluble anti-Ig for 48 h yields low density B cell blasts (anti-Ig blasts) that proliferate and secrete IgM when recultured with either LPS or T cell-derived lymphokines (1, 2). Culture of anti-Ig blasts with a mixture of T cell-derived lymphokines that includes IL-4 (EL4 Sn) (1, 2) results in secretion of IgGI, which is blocked by monoclonal anti-IL-4 (1) . Thus, IL-4 can alter Ig isotype expression in B cells pre-activated by anti-Ig . However, IL-4 alone does not sustain proliferation nor promote differentiation of anti-Ig blasts (1, 2), suggesting that other lymphokines are required to enable IL-4-induced IgGl secretion . We have examined the effects of other T cell-derived lymphokines on IL-4-mediated IgGI secretion . While IL-4 was capable of suppressing IgM secretion from LPSstimulated anti-Ig blasts, secretion of IgGI required lymphokines in addition to IL-4, including IL-5 and IL-2.

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Nubian ibex I would like to add to the information given in the article 'Nubian ibex in the Eastern Desert, Egypt' (Oryx, 20, 176-177). Israeli soldiers who were stationed at Jebel Ataqa (29 55'N 32 20'E) reported that during November 1973 they observed a group of Nubian ibexes on that mountain. The last report of ibexes from this area dates back to 1866 (Osborn and Helmy, 1980).

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