THE FIBRILLAR SYSTEMS OF CILIATES AS REVEALED BY THE ELECTRON MICROSCOPE. I. PARAMECIUM

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Abstract
1. Various structures in Paramecium are readily obtained for electron microscope examination by formalin fixation followed by sonic dissection. These structures include macronuclei, mitochondria, trichocysts in various stages of explosion and fragments of the pellicle. This study concerns such fragments. 2. The electron microscope reveals two fiber systems associated with the pellicular fragments. One of these is intimately associated with the pellicular membrane and corresponds to the outer fibrillar lattice system of earlier investigators. The second system is subpellicular and corresponds to the kinety, neuroneme, or inner fiber system. 3. The pellicle proper consists of a thin membrane with no obvious fine structure. The outer lattice system is a continuous network. It corresponds in position to the system of polygonal ridges in the pellicle. A thickening in the cross bars of the polygonal lattice represents the trichocyst attachment point. A ring-shaped structure is found in the center of each polygon. The cilium passes through this ring. A short distance from this ciliary ring a second, smaller ring-shaped thickening is frequently found. 4. The kineties are compound structures composed of discrete units. Each unit consists of three parts: a) the cilium which passes through the ciliary ring of the pellicle and terminates internally at b), the ciliary basal body or kinetosome. Each kinetosome gives origin to c), a tapering fibril which parallels the surface of the animal. These units are associated by their tapering fibrils. The fibrils from a longitudinal row of kinetosomes overlap in shingle-like fashion to form a tight bundle. This bundle is the kinetodesma of the light microscopist. The fibrils of the kinetodesma all taper toward the anterior end of the animal. 5. No obvious connection exists between the outer lattice system and the kinety system.