Differentiation for aggregation in the cellular slime moulds: the emergence of autonomously signalling cells in Dictyostelium discoideum.

The results of experiments on small populations of Dictyostelium discoideum, directed towards the measurement of the development in time of the competence of the cells to signal autonomously, are reported. This competence is quantified by X3, the intrinsic probability that a given cell may turn autonomous. The data show an early exponential growth in time of X3, followed by saturation. The saturation value depends on the population size suggesting that the differentiation is a co-operative phenomenon. The differentiation of autonomous cells starts roughly 7 h after the removal of food and saturates within 21 h.