Lincomycin added to the cultivation medium induced a number of changes in the organism producing it during its ontogenesis when grown recurrently on liquid media. It was found that lincomycin inhibited the culture growth and decreased the absolute amount of the antibiotic synthesized while the specific activity of the culture increased. A number of cytomorphological rearrangements relevant to the adaptive protective reactions was found. It is suggested that an increase in the resistance of the culture to the antibiotic produced by it at the late developmental stages is the result of the above protective reactions.