Merkwaardige verschijnselen bij Dictyosphaerium pulchellum Wood

In a shallow pond, dug in an oligotrophic area, but enriched by recreation, a waterbloom of a micro-organism which at first could not be identified was investigated. Cultivation showed a transformation into distinct colonies of Dictyosphaerium pulchellum Wood, which species was repeatedly recorded from the pond before. It might be possible that the observed cells developed from zygotes, but in fixed material collected earlier no indications could be found to state this. During the development of the culture the formation of colonies could be followed. The process starts with the formation of autospores. Division into 4 autospores occurs about 6 times as often as into 2. Deviations of the progress of the process may be explained by desynchronisation of the divisions and by dying off of the cells. The number of dying cells is considerable: 1 out of 5 cells dies before it is able to form new autospores.