AMEBOID MOVEMENT 83 



One of the most elaborate attempts that has been made toward 

 explaining ameboid movement on the basis of surface tension 

 phenomena was that of Biitschli ('92). From his extensive 

 knowledge of the lower organisms, especially the protozoa, he 

 concluded that protoplasm is an emulsion of two fluids: a more 

 concentrated "plasma," insoluble in water; and a thinner fluid, 

 "enchylema." Ameboid movement was brought about by migra- 

 tion of enchylema droplets to the surface of the ameba at the 

 anterior end, where they burst and spread over the surface, 

 lowering its tension. The effect of this change in tension was held 

 to be a flowing backward of the surface of the ameba and a 

 flowing forward of the endoplasm. This is what happens in a 

 drop of fluid, such as oil, on water to one side of which is brought 

 a soapy solution. Biitschli described many experiments with 

 fluids on which the surface tension was changed by appropriate 

 means to simulate the process of movement. After Biitschli had 

 developed his surface tension theory of movement, he discovered, 

 as has already been noted, that in a pelomyxa the surface layer 

 moves forward instead of backward as required by the surface 

 tension theory. In spite of this however he still maintained that 

 his theory of movement could be modified to apply to amebas 

 generally, although so far as I have been able to find, he did not 

 then or subsequently state how. From this we may infer that 

 Biitschli himself probably concluded that the surface tension 

 theory of movement as he developed it, is not of general applica- 

 tion or is nothing more- than a step in the development of such 

 a theory. 



Rhumbler has writtten a number of papers on the mechanics 

 of ameboid movement, most of which are concerned with elabora- 

 tions and modifications of a surface tension theory very similar 

 to Biitschli's. Rhumbler published a general outline of his theory 

 in 1898. The transformation of endoplasm into ectoplasm at the 

 anterior end, and the reverse process at the posterior end, was 

 stated to be an important part of his theory of movement, but 

 'just how this was necessary to surface tension effects was not 

 explained in physical terms. Feeding was assumed to be caused 

 by the direct action of the food body on the surface layer (ecto- 

 plasm) of the ameba. The presence of the food body, he held, 



