Scanning Electron Microscopy of the Cortex of the Ciliate Stentor coeruleus. A View from the Inside

SYNOPSIS. A microdissection procedure was developed which permits the viewing of the inside surface of the cortex of Stentor coeruleus with scanning electron microscopy. Parallel bands of myonemes cover the entire inner surface of the cortex. The myonemes of the stalk region are ribbon‐shaped and lack cross connections. The myonemes of the anterior cortex are flattened against the surface and are interconnected by an extensive system of cross branches. The inner surface of the frontal field is covered with a regularly cross‐branched myoneme system which follows the curved pattern of frontal field kinety. The observed branching patterns and shapes of the myonemes support the hypothesis that they cause contraction of the cell. The membranellar root system was examined. Each membranellar root makes a 90° counterclockwise twist along its vertical axis (viewed from the inside) as it descends into the cell. The outer edge of each root fuses with the inner edge of the adjacent one, forming a continuous fiber sheet linking the roots together.