The differentiation of the acrosome in the spermatid of the budgerigar (Melopsittacus undulatus).

The development of the acrosome of the budgerigar spermatid was studied under the electronmicroscope. The acrosome arises from a granule derived from the Golgi apparatus which interacts with the nucleus to form a cone shaped acrosomal cap and a perforatorium. A quanity of cytoplasm and plasma membrane is captured from the cell periphery and incorporated into the substance of the acrosome. The possible significance of the developmental phases and comparative avian spermatology is discussed.