The segmentation of aggregates into clusters of fruiting bodies and the formation of side branches all represent the formation of multiple body axes that are initiated by newly emerging tips (Fig. 4) . Analogous to the phenomenon of apical dominance in plants, where lateral shoots are suppressed by the primary shoot, (49) D. discoideum tips suppress the formation of ancillary tips. D. discoideum tips are selforganizing pacemakers for cAMP waves. The waves are propagated through the cell mass by cAMP-induced cAMP production, also known as cAMP relay.