The highest concentration of parasomal sacs is found in the oral region associated with the three ciliary membranelles, called in Paramecium, the ventral amd dorsal peniculi and the quadrulus. This micrograph shows the four rows each of the two peniculi, dorsal and ventral, and a large accumulation of coated vesicles and early endosomal cisternae immediately below the basal bodies. Two rows of parasomal sacs border the closely packed peniculi and a third row separates the two peniculi. Four rows of parasomal sacs interdigitate with the 4 rows of more loosely associated cilia in the quadrulus. TEM taken on 1/25/74 by R. Allen with Hitachi HU11A operating at 75kV. Neg. 19,500X.