A large proportion of bond^Z0165 mutant spermatids have one large nebenkern with four nuclei of normal size, indicating a cytokinetic failure in both meiotic divisions. A smaller proportion have two nuclei and a large nebenkern, indicating failure of only one of the meiotic divisions. A small proportion (<6%) of bond^Z0165 spermatids have 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. Further, occasionally spermatids are seen (<4% of cases) with more than four nuclei, which may result from defects in the mitotic divisions preceding mitosis. bond^Z0165/Df(3R)hh mutants also contain spermatids with four nuclei, and to a lesser extent two nuclei, but do not contain spermatids with either three or more than four nuclei. Spermatocytes of bond^Z0165 mutants lack an organized central spindle and an F-actin ring throughout ana-telophase. The equatorial anillin band is present but fails to constrict properly. bond^Z0165/Df(3R)hh mutants show the same phenotype.