Zum Problem der sexuellen Fortpflanzung in der PeridineengattungCeratium

On the basis of older literature and our new observations, a hypothesis is presented to illustrate our present view on the sexual cycle of the Ceratia. In the fresh-waterC. cornutum it has been possible to demonstrate that the “Knäuelstadium” ofBorgert (1910) represents in fact the postzygotene of meiosis. Formerly the “Knäuelstadium” was considered to be a stage of mitosis but, contrary to this view, occurs only in the Praeceratia, i. e. the swarmers emerging in spring from the germinating cysts (Scoczylas 1958). The “Knäuelstadium” has also been observed in marine Ceratia, but in cells of normal shape (Borgert 1910,Schneider 1924), which therefore function as meiocytes. The microswarmers (truncata-, lineata- andlata-forms;Lohmann 1908,Apstein 1910, 1911, and others) are the male gametes which copulate with females similar to vegetative cells, and which in this process are completely (flagellums?) resorbed by the latter. Stages of copulation have been observed in preserved material byApstein (1911),Borgert (1910),Tschirn (1920) and by us, and in the living state inC. horridum also by us. The latter species is monoecious. The marine Ceratia therefore seem to be haplonts in which the zygotes cannot be distinguished from vegetative cells, neither by a resting stage nor by obvious differences in shape. The possibility of diplophasic mitosis, however, has not been excluded.