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SUMMARY: Observations of nuclear morphogenesis were carried out using a modification of the acid hydrolysis-Giemsa technique. Throughout the development cycles studied, nuclear division was found to occur by means of elongation of the chromatin bodies with subsequent medial constriction and separation into daughter structures. Nuclear division greatly exceeded septum deposition during the early phases of the developmental cycles and, as a result, coenocytic filaments were formed. Fragmentation of these filaments resulted in the production of single cells, short chains and short coenocytes like those found in the inoculum. No evidence for complex nuclear fusions or reductional divisions was obtained during any period of nuclear morphogenesis and chromatin body divisions were considered to be amitotic. A simple model explaining previously reported genetic recombination in the genus Nocardia is presented.