A large proportion of fro^Z1497 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 (<0.5%) 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. fro^Z1497/Df(3L)AC1 mutant spermatids also show these defects, in these mutants occasionally spermatids with more than four nuclei can be seen, which may result from defects in the mitotic divisions preceding mitosis. Additionally, a small proportion of fro^Z1497/Df(3L)AC1 spermatids contain nuclei of irregular sizes.