Cellular autonomy of the Gonyaulax circadian clock

Because of the long term persistence of free-running circadian rhythms in populations of unicells, several investigators have considered, but not demonstrated, a possible role for intercellular interaction in maintaining synchrony between individual cells. The experiments described here were designed to test more critically the possibility that there is interaction between cells, including those possessing only small phase differences. None was detected; the bioluminescent glow of the mixed cultures matched the algebraic sum of the independent control cultures.