Paramecium is heterokaryotic i.e., it possesses a dimorphic nuclear apparatus - a single large macronucleus which controls metabolism and one or more small micronuclei concerned with reproduction.
Related Theory
Heterokaryotic refers to cells where two or more genetically different nuclei share one common cytoplasm. This is the stage after Plasmogamy, the fusion of the cytoplasm, and before Karyogamy, the fusion of the nuclei.