Chromatin diminution in early embryogenesis of Ascaris lumbricoides L. var. suum.

The occurrence of chromatin diminution in early Ascaris lumbricoides L. embryos has been studied in detail, and it is shown that it is possible to preselect three characteristic types of mitoses: pre-diminution, diminution, and post-diminution mitosis. The first three embryonic mitotic divisions are of the pre-diminution type. Chromatin diminution occurs after the third mitosis, but there is a variation from embryo to embryo as to whether or not chromosomal diminution occurs during the fourth, fifth, and six divisions. However, the seventh embryonic division, which gives rise to an eight-cell embryo, always exhibits chromatin diminution. Subsequent mitoses of somatic cells already in the diminished state are of the post-diminution type of mitosis.