Cellular slime moulds are social amoebas. They literally blur the distinction between a social group of individuals and a single multicellular individual. In part of their life cycle, separate amoebas creep through the soil, feeding on bacteria and reproducing, as amoebas will, by dividing in two, feeding some more, then dividing again. Then, rather abruptly, the amoebas switch into ‘social mode’.
