Abstract
Interspecific conjugation was induced artificially between the distantly related species belonging to the two different morphological groups, ‘aurelia’ and ‘bursaria’ groups, of Paramecium. Cytological observations showed that the interspecific conjugants underwent normal nuclear changes, including meiosis. However, nuclear changes of co-conjugant cells did not synchronize each other. These results suggest that conjugation in Paramecium involves non-species-specific interactions and its interactions are sufficient for nuclear activation.