Fig. 24. Surface of the lens fiber, showing various membrane specializations associated with the mature cell. Rows of ball-and-socket interdigitations are found in the region of the angles formed by the fiber hexagon, whereas tongue-and-groove attachments are associated with the flat surfaces of the cells (Dickson DH, Crock GW: Interlocking patterns on primate lens fibers. Invest Ophthalmol 11:809, 1972)