The majority of dia^Z5930 mutant spermatids have one large nebenkern with four nuclei of normal size, indicating a cytokinetic failure in both meiotic divisions. A small proportion (<4%) have two nuclei and a large nebenkern, indicating failure of only one of the meiotic divisions, while 0.4% of spermatids contain three nuclei, which may be due to failure of cytokinesis in the first meiotic division, followed by budding off of only one daughter cell in the second meiotic division. dia^Z5930/Df(2L)TW84 spermatids show the same phenotype, except that 0.5% of these spermatids have more than four nuclei, which may result from defects in the mitotic divisions preceding mitosis. During telophase of dia^Z5930 mutant spermatocytes, the equatorial anillin band is discontinued and there is no contractile ring or organized central spindle. This phenotype also occurs in dia^Z5930/Df(2L)TW84 mutants.