[Not Available].

Antibiotics (30 mg/1) added at T 60 mn. lead, in a part of the population, to an increase of the macronuclear DNA content resulting from DNA activity during a phase S 2 which begins after the phase G 2. The largest cells have the highest DNA content and the longest generation time. The results are confirmed by autoradiography with tritiated thymidine. The percentage of macronuclear labelling increases from T 150 to a maximum at T 180, and it is greater with nigericin (46%) than with epinigericin (37%). Thus, epinigericin is less toxic than nigericin.