Elektronenmikroskopische Untersuchungen zum Formwechsel der Kinetochoren während der Spermatocytenteilungen von Pales ferruginea (Nematocera)

Longitudinal thin sections of preselected spermatocytes were studied with the electron microscope. The kinetochores of autosomes and sex chromosomes show a characteristic change of their form during the meiotic divisions. Just after nuclear membrane breakdown the kinetochore profiles have the form of circles, in early prometaphase they have flame shape, and in metaphase appear as straight zones. As early as prometaphase I two sister kinetochores are discernible in each kinetochore region of a dyad. In prometaphase the sister kinetochores of the sex chromosomes are connected with each other through condensation zones which are continuous with both kinetochores. A double line structure is often seen in kinetochores and condensation zones. The morphological change of kinetochores can be asynchronous, as is especially conspicuous in the sex chromosomes. —The mitotic apparatuses of Pales behave in hexylenglycol medium like mitotic apparatuses of marine eggs. Crystalloids (Fuge, 1970) and microfilament bundles (Bajer and Molè-Bajer, 1969) occur in mitotic apparatuses in early and middle prometaphase.