The microvilli of intestinal cells contain a highly or-ganized network of microfilaments. The central core of the microvillus is occupied by a bundle of polarized actin filaments, originating at the tip of the microvillus (Mooseker and Tilney 1975) and extending into a net-work made of actomyosin and intermediate filaments, called the terminal web. The terminal web is oriented perpendicularly to the microvillar axis. The actin mi-crofilaments in these bundles are linked to one another by cross filaments (Mooseker 1976). Laterally, these bundles are connected to the plasma membrane via bridge filaments (Murkerjee and Staehelin 1971; Moo-seker 1976; Matsudaira nd Burgess 1979). In these structures we can recognize two types of membrane linkages for the actin filaments. At the ape
