Demonstration of membrane-associated and oriented microfilaments in Amoeba proteus by means of a Schiff base/glutaraldehyde fixative.

After fixation with a reaction product of glutaraldehyde and spermidine phosphate Amoeba proteus cells show a network of cortical microfilaments and oriented bundles of thick and thin filaments. The cortical filament network appears to be membrane-attached and extends beneath the whole cytoplasmic membrane surface. In the uroid region and in retracting pseudopods the cortical layer is thicker than in advancing cell regions. The filament bundles are located predominantly in the ectoplasmic tube within the cortical network. They strictly parallel the cell surface contours.