Abstract
A fragment with only an abnormal oral apparatus (OA) was obtained by operation from a doublet of Glaucoma scintillans possessing one normal and one abnormal OA. This singlet could reproduce and produced a cell line. Singlets frequently possessed an inverted OA, whose antero‐posterior axis was rotated 180°. This inversion of the OA has been perpetuated through a considerable number of generations. Oral replacement commonly occurred in singlets with an abnormal OA regardless of growth phases of a culture. The position of the contractile vacuole pore, the direction of curvature of ciliary rows surrounding the OA, and the organization of postoral ciliary rows were mirror‐images of those of a normal singlet.