Mutation in the protozoan Paramecium multimicronucleatum as a result of x-irradiation.

Mutations have been produced in the protozoan Paramecium multimicronucleatum by repeatedly exposing clonal cultures of the animals to large dosages of x-irradiation. The descendants of x-rayed survivors showed the following changes, which persisted in culture: destruction and loss of all micronuclei, decrease in vitality and reproductive rate, increase in x-radiation sensitivity, monstrosity, and reduced body size.