AMEBOID MOVEMENT 125 



direction than in any other. This is brought out by the following 

 series of experiments. 



Of sixty cases of feeding on various kinds of particles, by as 

 many different amebas, in which the direction of movement before 

 and after a particle was eaten was recorded, thirty-nine moved 

 off in the same direction after eating as before eating. By mov- 

 ing off in the same direction is meant that the ameba did not 

 move more than 22^2 to the right or to the left of the direction 

 of movement before feeding. The circle was thus divided into 

 octants, and the expectation of movement in the same direction 

 after eating a particle, if it were a matter of chance, would have 

 been seven and one-half cases instead of thirty-nine. 



But it is not only the process of feeding that has to be con- 

 sidered in this connection, for feeding occasionally is affected by 

 a side pseudopod while the main body of the ameba moves on 

 without being visibly affected as to its direction of movement. 

 No such case is included in the figures just given. In each of 

 these sixty cases the endoplasmic streams of locomotion were 

 completely stopped, from about twenty seconds to seventeen min- 

 utes. In most cases the endoplasmic stream was also completely 

 disorganized, the ameba assuming a nearly spherical form in which 

 more or less well marked though small cross currents of endo- 

 plasm could be detected. The direction of the light was without 

 effect, for the paths extended in every direction with respect to the 

 light both before and after feeding. Further, it has been shown 

 that ordinary diffuse light is without effect on the movements of 

 the ameba (Schaeffer, '17). It may be concluded therefore that 

 the ameba tends to keep on moving in straight paths even if the 

 highly disorganizing act of feeding and the consequent resting 

 period of a few seconds to many minutes supervenes at some 

 point in its path. To what this induction of the original path is 

 due is not clear, thought it is possible that the physical condition 

 fo the ectoplasm at the anterior end is different from that else- 

 where and that it requires less energy in consequence, or for some 

 other reason, to flow in the original direction. This explanation 

 is based on the observation that it is easier for the ameba to 

 activate the remnants of old pseudopods than to form new ones 

 (Schaeffer, '17). 



