AMEBOID MOVEMENT 143 



with the movements of the superficial films of Oscillatoria fila- 

 ments, diatoms, crawling euglenas, and probably also Gregari- 

 nidas, indicates that the superficial films of all these organisms, 

 including amebas, are all activated by surface tension changes. 

 Thus instead of postulating several methods of locomotion which 

 are fundamentally different from each other, for these respective 

 organisms (excepting the ameba), one explanation serves the 

 purpose; and it has the further merit of agreeing more nearly 

 with observation than the various other theories proposed. 



From the point of view of ameboid movement, the discovery 

 of the surface film and its activities narrows down the problem 

 very considerably. It does not help directly perhaps, in the solu- 

 tion of ameboid movement, but it shows clearly that the region 

 where ectoplasm is most rapidly formed (at the anterior ends 

 of pseudopods) is also the region where the superficial tension is 

 increased. This therefore gives us somewhat of an insight into 

 what must take place during the transformation of endoplasm 

 into ectoplasm. 



Although the wavy path of the ameba does not at present relate 

 itself to any other process in the ameba, it is bound to be of the 

 greatest significance in investigating the intimate nature of proto- 

 plasm while in movement. In so far as the wavy path concerns 

 the ameba, it effectively disproves the presence of that scientific 

 monstrosity, random movement. The path of the ameba is 

 orderly. 



The wavy path of the ameba represents a projection on a plane 

 surface of a helical spiral. The path of the ameba is thus geo- 

 metrically related to the spiral paths of free-swimming organ- 

 isms such as ciliates, flagellates, rotifers, swarm spore's, worm 

 larvae, etc. But the paths are more closely related than merely 

 geometrically. The effects produced by temperature on amebas 

 and ciliates and flagellates indicate a relationship between the 

 physical processes underlying the control of the direction of the 

 paths traveled over in free movement. No causal distinction can 

 yet be made between rotation on the long axis and the spiral 

 swinging. 



The spiral path is not an acquired habit. It is not a habit that 

 has been developed to overcome asymmetery of body shape, for 



