A large proportion of bns^Z3021 mutant spermatids have one large nebenkern with two nuclei of normal size, indicating failure of cytokinesis in one of the meiotic divisions. Further, many spermatids have four nuclei and a large nebenkern, indicating a cytokinetic failure in both meiotic divisions. A small proportion of 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. In late telophase of bns^Z3021 spermatocytes, the actin ring is misshapen and contains excess F-actin compared to wild-type cells and seem to lack an internal lumen. Most anillin rings are more constricted than in wild type and ring canals are often smaller.