Abstract
The rules which hold for Acetabularia hold also for various other cell types: the regulation of nuclear and cytoplasmic activities, both of which are intimately connected by cyclic (feedback) processes, is based mainly on cytoplasmic energy production. Such changes in the nuclei which do not seem to involve energy production[long dash]e.g., the changes in amphibian nuclei[long dash]are caused by cytoplasmic conditions which cannot yet be specified.