AMEBOID MOVEMENT 51 



particle. The speed ratio of particle a to particle b was as 1.26 

 to i. 



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 n the particle had come to lie in the pos- 



Figure 16. Illustrating more rapid movement of the surface film in the 

 middle of Amoeba sphaeronudeosus 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. 



tenor 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 



