Circadian Rhythm of Cell Division in Euglena: Effects of a Random Illumination Regimen

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Science  01 Aug 1969:
Vol. 165, Issue 3892, pp. 500-503
DOI: 10.1126/science.165.3892.500


A persisting, "free-running," circadian rhythm of cell division in autotrophically grown Euglena gracilis is obtained upon placing either an exponentially increasing population or a culture that has been synchronized by a 10:14 light-dark cycle in a random illumination regimen that affords a total of 8 hours of light each 24 hours. These results are interpreted as implicating an endogenous biological clock which "gates" the specific event of cell division in the cell developmental cycle.