It is now clear from a wide range of research that cytoplasm is not merely a buffered solution of proteins and enzymes but contains a series of complex filamentous structures. The cytoskeleton is the collective term given to these filaments. There is a considerable amount of data available on the protein composition of the major filament systems (microfilaments, microtubules, and intermediate filaments) but we are still comparatively ignorant about the role of the cytoskeleton in cell physiology. However such major cytoplasmic components (actin and tubulin, the monomeric constituents of...