Fig. 2. Schematic illustration of a cross section of the cortical region of a Paramecium cell. The cilium (c) grows from a basal body (bb) inside the cell membrane (cm). The terminal plate (tp) separates the basal body and the upper region of the cilium. The trichocyst (t) and alveolar sac (as) are located in close proximity to the basal body. The diameter of the cilium is approx. 200 nm and the length of the trichocyst, 5 µm. Following exocytosis, the released trichocyst expands 25 µm in length.