Figure 36. Showing how smooth waves in the path of an Amoeba proteus in clavate shape become disturbed by the projection of prominent pseudopods. Although there was considerable disturbance due to the formation of pseudopods at 11:53 the conformation of the wave was not changed until the stage preceding the one at 12:07, when the formation of numerous pseudopods resulted in an irregular path. Length of the ameba, about 600 microns.
When a wave in the path for some reason becomes unusually long, there is likely to be a very abrupt and decided change in the direction of movement, which is away from the convex side of the wave. [Figure 37] is inserted here to illustrate this point. The ameba should have turned to the left at 3:43 to keep the waves of typical size, and at 3:45 a pseudopod was extended in this direction a short distance, but again the curve toward the right persisted. But at 3:48½ the ameba broke up into several pseudopods at right angles with the main axis, and through one
Figure 37. An illustration showing that sudden changes from the expected direction of the wavy path are centrifugal, not centripetal; that is, away from the focus of the wave, not toward it. The tendency to break away from the first smooth wave became apparent at 3:45, as indicated by the extension of pseudopods near the anterior end. In the stage about two minutes later, a number of small pseudopods were thrown out in various directions. At 3:48½ several large pseudopods were thrown out near the anterior end almost at right angles to the main axis, instead of at an angle of about sixty degrees or less, as is the usual case. The same thing occurred at 3:57, except that the angle of the pseudopod was not so large.
of these the ameba moved on with the reestablishment of the wavy path. The tendency to wave formation evidently has to overcome resistance of some sort.
Figure 38. Amoeba dubia usually moves with numerous large pseudopods, but this illustration shows that there is very good reason for concluding that there is a tendency in this ameba to move in wavy paths. Length of the ameba, 400 microns.
Although amebas in clavate shapes describe the smoothest waves in their paths, waves may also be detected in the paths of amebas that habitually form many pseudopods. The path of an Amoeba dubia is shown in Figure 38. The ameba moved on an opal surface under light-controlled conditions. If we had not already seen how proteus, discoides, and especially bigemma formed smooth waves in their paths, we should hardly be able to understand the apparently aimless path of dubia. But having seen how a regular succession of smooth waves appears under favorable conditions in the paths of these amebas, there can be little question but that the staggering path of a dubia also is to be interpreted as a succession of waves, although they are somewhat irregular.