Physical Aspects of Protoplasviic Streaming 243 



ism is not rhythmic. If the rhythmic activity of each structural unit 

 be of a random nature both in regard to the phase and direction, 

 periodicity in the total mass will statistically tend to be canceled out. 

 Rhythm will be observable only when each unit cooperates or syn- 

 chronizes to a certain degree. 



Some Euglenae, e. g. E. deses, exhibit a characteristic change in 

 shape and attendant streaming of the endoplasm, which is generally 

 known as "euglenoid movement" or "Metabolie." This is a sort of 

 amoeboid movement in the sense that the streaming of protoplasm 

 involves a change in shape. Under normal conditions the movement 

 is quite irregular and with no indication of rhythm. It is, however, 

 very interesting to point out that when some Euglenae are trans- 

 ferred into acid solutions or subjected to other unfavorable condi- 

 tions, the movement soon begins to show almost perfect periodicity 

 for a considerable time before death takes place (Kamiya, 1939) . 

 The rhythm is in this case pathological, yet nevertheless, it does show 

 that a periodic mechanism is inherent in an organism which does not 

 exhibit any periodic movement whatever under normal conditions. 



In order to explain the streaming movements of protoplasm, 

 known as rotation and circulation, which observably are not 

 rhythmic, it may be necessary, regardless of the nature of motive 

 forces, to postulate a rhythmic cycle in the motor mechanism. 

 Indeed, rhythmic mechanism may exist in protoplasmic function, but 

 is concealed behind the non-rhythmic resultant. There is no reason 

 to believe that the mechanism responsible for other forms of rhythm, 

 such as ciliary movement, is essentially different from that respon- 

 sible for protoplasmic streaming. It is, however, a problem left for 

 the future, how far rhythmic mechanism is a universal attribute 

 of living matter. 



It is true that the energy used for protoplasmic streaming is 

 f irnished ultimately by respiration. But the rhythmic output of 

 meclianical energy (motive force) does not necessarily imply a 

 rhythmic pattern in respiratory function. A periodic mechanism may 

 be ascribed to any definite part in the total chain of intraplasmic 

 reactions. 



According to the view advanced by Professor Seifriz (1937, 

 1938) , streaming in slime molds is caused by a "rhythmic contrac- 

 tility" of the protoplasm, due probably to the shortening of protein 

 fibers by molecular folding or, possibly, helical contraction. Although 

 it is not within the scope of the present paper to indulge in specu- 



