The Dissociation of Morphogenesis from Cell Division in the Cellular Slime Mould, Dictyostelium discoideum

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Abstract
Dictyostelium discoideum, strain Fty-1, myxamoebae were harvested from the stationary phase and dispensed in small population samples on washed agar. Total cell counts were made at intervals between deposition and fruit construction. Within an uncertainty level of 2.5%, the data indicate that the populations remained constant and the terminal fruits contained the same number of cells as had formed the aggregates. Subsidiary evidence based on viability determinations and the known morphology of moribund cells suggested that new cells did not arise nor old cells die. When myxamoebae were harvested from the log phase while still feeding on a high density of bacteria, a substantial degree of cell division did occur during morphogenesis. But the increase in cell number of myxamoebae which had not aggregated corresponded approximately, with that of myxamoebae which had aggregated and fruited. Consequently such increases appear to be coincidental with and not causally related to the morphogenetic sequence.