96 LIBBIE H. HYMAN 



surprise to me that Rhumbler's explanation of amoeboid move- 

 ment in forms with gelatinized surfaces has not received wider 

 recognition. In this paper, I have only attempted to restate 

 his theory in the light of my observations on the presence of 

 the pseudopodial gradients, which necessitate the conclusion 

 that the mechanism of amoeboid movement is internal. 



SUMMARY 



1. A gradient in susceptibility to potassium cyanide exists in 

 each pseudopodium of amoeba. The suscepibility is greatest at 

 the distal end and decreases proximally. The most recent or 

 most recent vigorous pseudopodia are the most susceptible. 



2. An amoeba is therefore temporarily differentiated into 

 anterior and posterior ends, the region or regions of highest 

 susceptibility being the anterior end or ends as in other organisms. 



3. It is shown that the susceptibility gradient, which is a 

 metabolic gradient, arises in the amoeba before the pseudopodium 

 appears and hence the metabolic change which produces in- 

 creased susceptibility is the primary cause of pseudopodium 

 formation. 



4. Evidence is adduced to show that the surface of most amoe- 

 boid organisms is in a state of gelation 



5 From 3 and 4, it is argued that amoeboid movement must 

 be due to alterations of the colloidal state Liquefaction or sola- 

 tion is regarded as the cause of the extension of a pseudopodium, 

 and coagulation or gelation of the withdrawal of pseudopodia 

 and of active contraction The liquefaction is believed to be 

 brought about by the metabolic change referred to in 3. 



6. Attention is directed to the fact that this theory is only 

 an extension of one previously advanced by Rhumbler. 



