The movement of particles on the under side of an _Amoeba sphaeronucleosus_ depends upon what part of the ameba is attached to the substratum. Where the ameba is attached there is of course no movement of the surface layer and the particles remain stationary. In an ameba attached as shown in figure 20, _a_, there was a very slow movement of particles forward near the middle of the attached region (x), but whether this was related to the movement of the outer layer of the upper surface was not determined. The movement of these particles was considerably slower than the movement of the ameba. In another ameba attached at the anterior and posterior ends (Figure 20, _b_) no movement of particles on the under side could be discerned. The small particles showing Brownian movement, with the surrounding water, are dragged along as a mass. This movement is purely mechanical, and is what would be expected on purely physical grounds, when a more or less cup-shaped object is moved along in water in close contact with a flat surface. Such particles as have become attached to the surface layer on the under side of the ameba, because of their slower movement than that of the ameba, eventually bring up at the sides near the posterior end, as the ameba moves along. From here they are carried forward in the manner already described. Thus there comes about a “rotation” of particles adhering to an ameba as described by Jennings (’04) and Dellinger (’06), though the explanation is different from that given by Jennings (l. c.) as we shall see further on. No case of a similar rotation of larger particles which had sunk into the ectoplasm, as described by Jennings (’04, p. 142), has come under my observation. [Illustration: Figure 20. _Amoeba sphaeronucleosus_. _a_, the under side of the ameba. The part of the ameba attached to the substratum is stippled. Particles attached to the surface film at _x_ moved slowly forward. _b_, the under side of the ameba, showing the attached parts stippled. The particles suspended in the water at _x_ moved slowly forward with the ameba. _c_, a cross section of an ameba of shape shown in _b_, showing the ridges on the surface. Length of the ameba, about 100 microns.] The movement of the surface layer in _A. verrucosa_ is quite like that of _sphaeronucleosus_. Figure 21 shows a group of three particles carried by a _verrucosa_ while changing its direction of locomotion. The particles changed position with regard to each other and they moved at different speeds. Particles _a_, _b_, _c_, moved respectively 2.40, 3.26, 2.85 times as fast as the ameba advanced. Other experiments indicate that the outer layer of _verrucosa_ moves at about the same speed, compared with the speed of the ameba, as that of _sphaeronucleosus_.