Figure 1. Diagram to illustrate the principles believed to drive the movement of Amoeba. Actin filaments exist in the cortical ectoplasm, and are capable of exerting contractile pressure on the more fluid endoplasm. Contraction of ectoplasm at the tail end (left) causes solation of the cytoplasm and depolymerization of the actin filaments. The pressure created propels endoplasm towards the right through a tube whose walls exert enough tension that endoplasm only escapes at the tip of the extending pseudopod (right end). Here endoplasm spreads and gelates to extend the ectoplasmic tube, as actin filaments repolymerize. (Modified from Sleigh, 1989.)

Figure 2. Comparison of the propulsion of water (red arrows) by a flagellum (a) with that by a cilium (b) as a result of motion by these organelles indicated by blue arrows (see text). (Modified from Sleigh, 1974.)

Figure 3. Comparison of (a) the action of dynein molecules (d) in generating sliding motion between two microtubules, A and B, with (b) the action of a myosin filament (m) in drawing together the attachment points of two actin microfilaments (mf) (see further description in the text). (Modified from Sleigh, 1989.)