AMEBOID MOVEMENT 87 



boid movement. It will give our first real insight into the chem- 

 istry of ameboid movement. The fact that her method of demon- 

 strating gradients has yielded uniform results in the hands of 

 Child ('15), who originated it, as well as in her own when applied 

 to a great many different organisms, entitles her conclusions to 

 careful examination. 



Of the observations there can be no doubt, for in many details 

 earlier observations are confirmed. Her figures show that the 

 tips of the pseudopods disintegrate first in the potassium cyanide 

 solution and later the regions further back (Figure 30). The 



Figure 30. Disintegration of an ameba in % molecular KNC. After 

 Hyman. a, ameba flowing in the direction of the arrow, b, the ameba 

 has abandoned pseudopod i and flows into pseudopod 2, which has become 

 reactivated. The ameba was exposed to KNC at this stage and, as is 

 usual in such experiments, the posterior end at x becomes active, c, the 

 youngest pseudopod, at x, disintegrated first, d, the next youngest pseudo- 

 pod, 2, disintegrated next. Pseudopod i, the oldest, disintegrated last. 



question is, what causes the gradient of disintegration, which 

 Miss Hyman takes to represent also a metabolic gradient ? Where 

 is the gradient located: in the ectoplasm or in the endoplasm; 

 or is the gelation process synonymous with the metabolism that 

 gives rise to the observed gradient ? Miss Hyman does not 

 say ; but it cannot be in the endoplasm, for it is in motion along 

 the whole pseudopod at about the same rate and it undergoes a 

 demonstrable and visible change only at the anterior end of the 

 pseudopod. While metabolic changes might be higher at the free 

 end of the pseudopod, therefore, there would not be a gradient 

 from there on back. No recorded observations on the endoplasm 

 along the length of a pseudopod can be arranged so as to form 



