The aggregation centers ofDictyostelium minutum have three functions: 1. they cause a chemotactic reaction, 2. they induce a change of the cells' functional state which enables the cells to establish intercellular contacts, 3. in some strains, they induce the foundation of further centers.Cells of this species, before being included in a center, are unable to join each other. From this results en exceptionally simple and clearly arranged aggregation pattern, because the assembling of aggregating cells into streams is omitted.