In some cells, after interphase and nuclear division, cytoplasm division does not occur and more than one nucleus is formed within a cell. This division, in which multinucleated cells are formed, is called endomytosis. The multi-nucleated striated muscle cells of most animals are caused by cell fusion, not endomytosis. Endomytosis is the reason why paramecium is double core or pollen has two nuclei, vegetative nucleus and generative nucleus.