The activity and localization of the mitoses in the retina of an adult Teleost (Carassius auratus) was checked at various periods after the removal of a quarter of neural retina. The mitotic activity starts at the 7th day and reaches high values at the end of the first month, then decreases and disappears two months later. At the beginning of the restitutive process most of the mitoses are located in the ora serrata, but afterwards they are found near the cut borders, in the blastema. This shows that the blastema of the regenerating retina is mainly formed by cells coming from the ora serrata. The constant presence of mitoses in the old retina suggests that the neuroblasts found here participate in the regeneration of the new retina. The lack of mitoses in the pigmented epithelium (tapetum) indicated that this layer is not involved in the retinal regeneration.