[Demonstration of a regenerating activity in the rhynchobdellid leech Helobdella stagnalis]

After amputation of the posterior region of the body, Hirudinea Helobdella stagnalis is able to regenerate. This faculty, which involves the whole posterior part in the young, still persists in adults but is limited to the posterior ventouse and depends on the presence of the terminal nerve ganglion on the surface of the transsection area. Histologic study in young and adults demonstrates that morphogenesis activity restriction, in this body region, is due to irreparable loss of neuroblastic potentialities of healing epidermal cells.