CHAPTER XII 

 THE WAVY PATH OF THE AMEBA 



In the preceding chapters we discussed the various factors which 

 characterize ameboid movement : the streaming of the endoplasm, 

 the formation of ectoplasm, and the behavior of the surface film. 

 The discussion has involved only momentary cross-sections of 

 the life of an ameba, following the method of investigation in 

 general use for the solving of problems connected with ameboid 

 movement. It has been tacitly assumed that if one could explain 

 ameboid movement at any particular cross-section in time, one 

 understood the whole process of ameboid movement no matter 

 how long it continued, excepting, of course, the action of various 

 kinds of stimuli that produced changes in direction, speed, etc., 

 of streaming. It was not assumed that time was an element in 

 the practical sense in the explanation of locomotion. A few seconds' 

 or a few minutes' comprehensive observation was supposed to 

 furnish sufficient basis for an explanation. 



Sometime ago I discovered however that the path of an ameba 

 as it moves over a flat surface free from particles possesses 

 character ; it is not an aimless irregular zigzagging here and there, 

 such as has been generally supposed, and in occasional instances 

 asserted, to be the case. On the contrary, the path of an ameba 

 during the course of an hour or two consists of a succession of 

 gentle right and left-hand curves alternating with each other. 

 The general appearance of the path is that of a flattened spiral. 

 Having observed a part of an ameba's path, therefore, one can 

 predict with considerable accuracy in what direction the ameba 

 will continue to move. Thus that scientific bugaboo "Random 

 Movement" is evicted from that strongest of his strongholds, the 

 aimless wanderings of the ameba. 



The mechanism producing the sinuosities in the path of the 

 amebas is easily disturbed by external or internal stimulation of 

 various sorts, resembling in this respect the spiral path of a para- 

 mecium, which is also easily changed by the presence of various 



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