In the earlier stages the outer layer was pulled toward the tip of both pseudopods, in the later stages only toward one, and in this lies the explanation for a more rapid movement of the particles in the earlier, and a slower movement in the later stages. This effect was also observed in _discoides_, but the fact that the particle in the later stages moved only very little faster than the ameba is due to a narrow anterior edge and to the formation of ectoplasm in the ridges over the surface of the ameba. The effect of ridge formation on the movement of particles attached to the surface film is well seen when an ameba has two forward moving regions opposite each other. Under such conditions particles located equidistant or nearly so between such regions, move only very slowly or not at all, the pull upon the film being nearly or quite equal. In a similar manner the ridges which are constantly forming on a _proteus_ are continually competing with the anterior end in their pull upon the surface layer, thus preventing rapid forward movement. [Illustration: Figure 26. Showing the comparative rate of movement of the surface film over the retracting parts of the ameba. In figures 2 to 8 only a part of the ameba is shown. Length of the ameba, 500 microns.] Figure 26 shows that the surface layer flows away from the tip of a retracting pseudopod that is located near the anterior end. The particle moves slowly until the body of the ameba is reached, when movement becomes more rapid, 8, 9. This proves that the third layer moves away from the retracting parts of an ameba, no matter how large the total area of these parts may be in proportion to the area of new surface that is being made. But whether the speed of the moving third layer changes in correspondence with a larger or a smaller ratio between building and retracting ectoplasm has not been ascertained. Figure 27 shows that the relative positions of particles attached to the surface layer may readily change while the ameba deploys its psuedopods. Three particles marked _a_, _b_, _c_ and connected [Illustration: Figure 27. A part of an _Amoeba proteus_ illustrating what is perhaps the most characteristic quality of the surface layer of amebas, its fluid nature. Three particles, _a_, _b_, _c_, were moving forward along an actively growing pseudopod. In stage 2, particles _b_ and _c_ had arrived nearly at the tip of the pseudopod. A pseudopod was then thrown out on the right, which resulted in the movement of _a_ in the same direction, while _b_ and _c_ remained nearly stationary. Later on this pseudopod was retracted. _b_ and _c_ were drawn back toward the main body of the ameba while _c_ remained behind, moving only very slowly. Thus the relative positions of these particles was completely changed.]