CHAPTER III 

 PHYSIOLOGY OF STREAMING MOVEMENTS 



SECTION 20. General. 



WE are here concerned with the connexions between streaming move- 

 ments in general and the other vital functions, as well as with those 

 phenomena of protoplasmic movement which we are unable at present to 

 directly refer to simple physical and chemical causes. Instead, therefore, 

 of adopting the analytical treatment, the phenomena in question will be 

 discussed from a purely experimental and empirical point of view. It must, 

 moreover, always be borne in mind that obscure internal stimuli or internal 

 changes which can neither be predicted, estimated, or controlled may 

 frequently modify the velocity of streaming, and sometimes to such an 

 extent as to vitiate the accuracy of results obtained by special experimen- 

 tation. Thus a stimulus to streaming, when once applied, may cause 

 little or no effect to be exercised by stimuli which markedly influence 

 normal unstimulated cells. Hence, in comparative experiments, it is of the 

 utmost importance that the material used should have been kept for some 

 time previously under uniformly and homogeneously optimal conditions, 

 and should be at approximately the same stage of development. 



Among the internal influences which affect streaming, those radiating 

 from the nucleus are undoubtedly of great importance, although they 

 appear to act mainly in an indirect manner, and not to exercise any directly 

 appreciable controlling influence. Streaming is always dependent upon 

 katabolism of some kind or other, although this need not necessarily take 

 the form of oxygen-respiration. The amount of dependence upon other 

 functions, however, varies, and the physiological importance of streaming 

 may alter according to external circumstances. 



Certain streaming movements of the protoplasm are not directly con- 

 nected with any vital functions whatever, but have a purely physical origin. 

 This is the case with the movements in mass of the protoplasm which 

 commonly occur in the mycelial filaments of many Fungi l . These may 

 continue or may be induced for a short time in the absence of oxygen, but 



1 Cf. J. C. Arthur, Ann. of Bot., 1897, Vol. xi, p. 491.' 



