EFFECTS OF RADIATION ON THE GROWTH OF EUGLENA CELLS

were irradiated in distilled water by 1-ray doses of 1 to 3 X 10 ' r for 30 to 90 minu-tes and by neutron units of 4.1 x 107 to 5.4 x 1012 n/cm2 for 10 to 90 minutes. No apparent difference was observed between both effects of 1-rays and neutrons on the growth of the cells. Many cells survived these irradiations. But, some remarkable effects were observed on the growth, the death and the albino mutation rates of the irradiated cells. And the degree of these effects was in proportion to the irradiation dose in most cases. Cells immediately after irradiation and their posterity after several generations reach the stationary phase of the culture at 10 to 25 % lower cell concentration than the non-irradiated cells. For a lethal dose, LD-50 (11-13) of Euglena cells required about 2 to 3 x 102 r of 1-rays for 60 to 90 minutes and about 3.6 x 1012 n/cm2/60 min. of neutrons. The rapidly growing cells were generally more radioresistant than the cells of stationary culture. Not immediately after, but several generations from both irradiations, a little dif-ference of cell size was observed between irradiated and non-irradiated cells. Albino mutants of the cells are easily induced by I and neutron irradiations.