The midgut epithelium of Oxidus gracilis consists of differentiated cells and regenerative cells. Only the first have many contacts with the surrounding liver cells. The fate of all three cell types has been examined during moulting. The regenerative cells divide at the beginning of moulting. They become cylindrical and form a closed ring basally of the differentiated cells which are pushed in the gut cavity. The contact area of the differentiated cells with the basement membrane becomes smaller and the processes of the basal labyrinth are long and thin. The apical adjoining region is filled with vacuoles containing non-colourable, refractive inclusions. They are ovoid, rounded with membranes and look like typical concrements. In the cell apex no inclusions are visible, the cytoplasm is dense. The nucleus is shifted to the apex and gives the impression of metabolic activity. A microvillous border is still present. At the same time the number of cytosomes in the liver cells is increasing continuously. After ecdysis the differentiated cells in the gut cavity have disappeared. One part of the former regenerative cells becomes differentiated to active midgut cells, the other part rests probably as juvenile cells. Most cytosomes in the liver cells have disappeared.