The brains of sti^dck2 and sti^dck2/Df(3L)E44 mutants have high proportions of polyploid cells. However, the chromosomes of these cells are morphologically normal and the mitotic index is similar to wild type. In very late telophases of sti^dck2/Df(3L)E44 neuroblasts, the frequency of intercellular bridges is higher than wild-type, suggesting that completion of cytokinesis takes longer in the mutant. Earlier steps of cell division, such as spindle formation and constriction of the cytokinetic ring, is not affected in the mutants. The testes of sti^dck2 males contain abnormal spermatids that have large nebenkerns associated with two or four normal-sized nuclei, which results from a failure of cytokinesis. This phenotype also occurs in sti^dck2/Df(3L)E44 males. Late telophase figures of sti^dck2/Df(3L)E44 spermatocytes often show overconstricted anillin rings that result in small ring canals.