Differentiation During Regeneration Caused by Migration of Repressors in Bioelectric Fields

Experiments are reviewed which have led to the conclusion that differentiation occurs during regeneration in Tubularia only if a bioelectric field of sufficient strength is maintained. The electrical polarity seems to determine the polarity of morphogenesis by controlling the movement of charged repressors. The repressors work in this totipotent system by preventing recipient regions from becoming what the donor regions are becoming. It appears that any level can become the most anterior structure not forming anterior to it. Thus by a series of repressions in totipotent material all levels of a hydranth are established.