Continued high incidence of mutants in a Peruvian population of mice.

A second trapping of wild mice from two sites in a Peruvian river valley confirms the unprecedented high mutant incidence established by a previous trapping. It also shows that the population may be localized. The new mutants are different from those found in the first trapping, and thus indicate a continued source of mutagenic activity either external or within the gene pool of the population. A third study is underway.