IT has long been known that when a fertilized egg is flattened between two plates it may cease to divide. Zeuthen1 has shown recently that although cell division is inhibited, nuclear division may continue, so that many nuclei may be present in a single flattened cell. I obtained essentially similar results during the summer of 1951, at Roscoff. It Was found that, if the egg was not too greatly compressed, it would eventually divide and, once division set in, cleavage of the cytoplasm would continue until the normal ratio of one nucleus to one cell was re-established.