Fine structure of males and females of Intoshia linei (Orthonectida) is described. The ciliated and contractile cells have identical structure in both sexes. The cuticle covering the body consists of two layers. A bundle of fibrils is present within the ciliated cells. This bundle is parallel to the apical cell surface. The fibrills are arranged in a ring in each transversal ring of ciliated cells. The contractile fibrils in the muscle-like «contractile» cells are located in a periphery.