Figure 15. An Amoeba sphaeronucleosus with two particles attached to its upper surface film, one in the middle and one at the side. a moved 2.6 times as fast as the ameba while b, lying nearer the side, moved only 1.9 times as fast as the ameba. Length, 100 microns.
Particles lying near the side do not move forward as rapidly as those lying in the middle. [Figure 15] shows two particles, one of which, a, lying near the middle of the ameba, moved 2.6 times as fast as the ameba advanced in the region of the particle; while particle b moved only 1.9 as fast as the ameba in front of the particle. The speed ratio of particle a to particle b was as 1.26 to 1.
Figure 16. Illustrating more rapid movement of the surface film in the middle of Amoeba sphaeronucleosus than near the edge. The vertical lines connecting the particle with the ameba outlines were drawn only for convenience of reference. Length of ameba, 120 microns.
[Figure 16] shows a particle lying still more to the side than in the preceding figure. In the first six stages the particle moved 1.85 times as fast as the ameba. The particle then came to the edge. From stage 7 to 10 the particle moved more slowly than the ameba. At stage 11 the particle had come to lie in the posterior half of the ameba, where the tendency of the surface layer is to travel toward the middle of the upper surface. In stage 12 the particle had gotten away from the edge of the ameba and already shows a gain in speed. From stage 13 to 16 the particle moved again about 1.83 times as fast as the ameba. But at stage 16 the edge was reached with a consequent decrease in speed of the particle.
The direction of the path described by a particle carried on the back of an ameba depends upon what part of the ameba is most rapidly forming ectoplasm. That is, the particle tends to
Figure 17. Illustrating the different speeds with which particles move when attached to the surface film of an Amoeba sphaeronucleosus, depending upon their location. Particle a moved 3.5 times as fast as the ameba and b 2.7 times as fast. Length of ameba, 110 microns.