| Abstract: | Ciliated cells in the rostral epidermis of amphioxus have been serial sectioned and examined in the electron microscope. The cells have a basal axonic process, which can be traced to the subcutaneous nepve-bundles, and hence these cells are primary sensory cells. Apically only the cilium, which takes its origin from an invagination, and a surrounding corolla of microvilli are exposed to the surface. Cross-striated filament bundles closely associate with a basal body and accessory centriole. One such bundle continues into the central part of the cell, while another bundle is attached at the lateral membrane. Between adjoining cells there are apical zonulae adhaerentes, and also poorly developed septate junctions. In addition, a third cell junction is described. Rod-like structures in the surface interdigitations are shown to be continuous with a peripheral layer of microfilaments. The choanocyte-like appearance of the ciliated cells and their resemblance to similar cells in various invertebrates are discussed. |
