CHAPTER IX 



The observations recorded in the preceding two chapters, while 

 they do not tell us anything about the direct cause of the move- 

 ment of the surface layer, nevertheless indicate clearly enough 

 that the area where ectoplasm is made is the area toward which 

 the surface film flows. There is no question therefore of the 

 intimate relation between the transformation of endoplasm into 

 ectoplasm and the movement of the surface layer. 



The apparent absence of movement in the surface film of the 

 pseudopods of Difflugia (Schaeffer, '17) and the definitely proved 

 absence of movement in the surface layer in the foraminiferan 

 Biomyxa and myxomycete plasmodia, where no ectoplasm is 

 formed in the manner observed in amebas, also indicates a causal 

 relation between movement of the surface layer and ectoplasm 

 formation. The relation moreover seems to be a necessary one 

 for the movement of the surface layer is contrary to the processes 

 involved in locomotion. In other words, from the standpoint of 

 the ameba, it is a "necessary evil," so far as locomotion is con- 

 cerned. 



The transformation of endoplasm into ectoplasm is unfortun- 

 ately not understood, though from what we know in a general 

 way of the behavior of colloidal solutions it seems to be a surface 

 tension effect due to (or accompanying) a change of phase. 

 Something akin to gelation occurs as Kite ('13) has shown. It 

 is a problem in the chemistry of colloids. But the structure or 

 composition of the protoplasm is complex and practically un- 

 known, and it is quite open to criticism whether analogies from the 

 behavior of pure solutions of colloids, such. as gelatin, afford any 

 real basis for an explanation. 



Although a knowledge of the movements of the surface layer 

 is interesting enough by itself, it will achieve its true importance 

 only when it can be related to other processes in the ameba in a 



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