Data represent percentage of spermatid type. 100% of wild-type spermatids possess a single nucleus and a single Nebenkern of regular size. In contrast, no spermatids in aust mutants exhibit regular morphology. Over 75% of onion stage spermatids possess a single large Nebenkern surrounded by four nuclei of irregular size. N refers to the size of the Nebenkern observed. N indicates a Nebenkern of regular size, 2× N indicates a Nebenkern twice the normal size, and 4× N indicates a Nebenkern four times the size of those seen in wild-type spermatids. Nu refers to the number of nuclei present. A and B indicate regular and irregular nuclear sizes, respectively.