Eva Hansen-Melander

Meiosis in Cepaea nemoralis studied by microcinematography

SummarySome aspects of meiosis in spermiocytes of Cepaea nemoralis L. are presented. They are based on in vitro studies with the use of time-lapse 16 mm film recording. The main results are:1.The nucleus changes its shape irregularly during diakinesis (and probably earlier stages) until the disappearance of the nuclear membrane. During this period the prophase bivalents inside the nucleus change their position and shape irregularly. Suggestions concerning the importance of such movements are made.2.In many spermiocyte divisions the spindle oscillates regularly in one or several planes. In all cells the periodicity is of more or less the same duration, about 2 mins.3.The volume of the nucleus diminishes during the 1–2 hour period before the disappearance of the nuclear membrane and increases again rapidly a few minutes before the nuclear membrane disappears. The disappearance of the nuclear membrane is followed by a rapid condensation of the space occupied by the chromosomes (contraction stage). This space increases again during prometaphase. The latter events closely resemble those in mitosis of plant endosperm cells.