SYNOPSIS. Transection and repair in Blepharisma intermedium modify the distribution of several enzymes. The number of active phagosomes is reduced and there are increased staining reactions for acid phosphatase, the nucleases and type‐B esterases in the ground cytoplasm. 5'‐Nucleotidase activity is localized in the cytoplasmic matrix. Except for ribonuclease, the enzymes may have a perimacronuclear deposition at some period during regeneration. Acid phosphatase may be involved in development of the oral membranelles. Adenosine triphosphatase and lactic dehydrogenase have a moderate staining intensity whereas malic and succinic dehydrogenases have a strong reaction in the cytoplasm; in addition, these enzymes may be localized in the kinetics involved in the neoformation of the oral concrescence. Nuclear reorganization is attended by an increased frequency of peripheral dehydrogenase activity in the late stages of regeneration. These observations are compared with catalytic systems known to function in protozoan metabolism and in vertebrate regeneration.