Spermatogenesis and spermiogenesis in Ascaris lumbricoides Var. suum.

Reorganization of the prophase I nucleus marks the beginning of the first meiotic division. A pair of centrioles is present at each pole at metaphase I and mitochondria are not observed in the spindle area. A chromosomal pellicle, which resembles a kinetochore plate but has no apparent association with microtubules, surrounds each autosome at metaphase I and II. The sex body lags behind the autosomes at anaphase I and segregates differentially to one daughter cell. Mitochondria and a pair of centrioles are present in the spindle during the second meiotic division. Localized condensation of chromatin and fusion of the condensed chromatin of the secondary spermatocyte telophase nucleus results in a compact spermatid nucleus. Loss of spermatid cytoplasm is effected by the ejection of a cytophore vesicle.