Macronuclear Regeneration in Epistylis Articulata

ABSTRACT The reorganization of the macronucleus from the vegetative micronucleus is described in Epistylis articulata (Ciliophora, Peritricha). Individuals which have accidentally been deprived of a macronucleus during binary fission develop a new one from the micronucleus. In such amacronucleate animals, the micronucleus divides into two, one of them growing into a macronucleus, the other remaining as the micronucleus. The phenomenon throws new light on the relative importance of the two parts of the ciliate nuclear apparatus and brings into greater emphasis the undifferentiated nature of the micronucleus. It also establishes the possibility of de novo synthesis of DNA in the developing macronuclear rudiment.