In another observation the effect of a narrowing of the advancing tip of the ameba is shown very well. In figure 24 the ameba was advancing with a broad anterior end, as shown at 1 and 2. From 2 to 4, the region where new ectoplasm was made, narrowed down very considerably. These changes in the width of the anterior end are reflected, as in Figure 17 by a decrease in the relative speed of the moving particle. Thus the particle moved 1.75 times as fast as the ameba from 1 to 2 while from 2 to 4 the particle moved only 1.27 times as fast as the ameba. [Illustration: Figure 24. Showing the effect of a narrow anterior end on the rate of movement of the surface. Length of the ameba, about 320 microns.] The movement of the third layer in _proteus_ is difficult to study owing to the formation continually of ridges, as explained on page 20. Even in clavate shaped amebas, waves of protoplasm are pushed out on the sides and on the tip with consequent formation of ectoplasm, so that the ameba grows in width slowly at the same time that it grows in length. A typical shape of a _proteus_ in clavate form is slightly tapering toward the anterior end. This shape is maintained by gradual extension of the sides of the anterior half or two-thirds of the ameba as it moves along. These conditions are just the reverse of what was seen to be the case in _sphaeronucleosus_ and _verrucosa_, where the anterior edge was wider than any other part of the body. But _discoides_, although free from the ridges and grooves characteristic of _proteus_, frequently has an anterior edge that is narrower than any part of the body, thus necessitating extension of the sides as the ameba moves forward. Let us now see what is the effect of ridge formation upon the movement of the surface layer. Figure 25 shows a _proteus_ and a narrow anterior end in _proteus_ with two pseudopods and a particle attached to the side of the ameba at 1. Both pseudopods advanced until stage 4 was reached, but the particle was not appreciably deflected from an approximately straight path by the small pseudopod at the other side of the ameba. Reference to the figure shows that the particle travelled much faster while the pseudopod on the side was extending than after it began to retract. The particle moved 1.43 times as fast as the ameba from 1 to 4. But from 4 to 7 the particle moved only 1.06 times as fast as the ameba. [Illustration: Figure 25. _Amoeba proteus._ Rate of movement of the surface layer as compared with the rate of movement of the ameba. The pseudopod on the right was extended to stage 5; from then on it was retracted, as indicated by the outlines. Length of the ameba, 400 microns.]