Physical Aspects of Protoplasmic Streaming 211 



ity to pressure variations, the experimental data obtained would 

 seem to have a high degr-ee of accuracy. 



The measurements were made at room temperature (22°-25"C.) , 

 which deviated not more than 0.5°C. during the time of experiment. 



In all the following figures, the abscissas represent the balance- 

 pressure applied to B (Fig. 5) , but they are equal to the vital motive 

 force, if the direction from a to b is regarded as positive and the 

 opposite direction, viz., from b to a as negative. 



Figure 6 represents the usual and most regular change in the 

 motive force. The undulating curve is beautifully smooth and the 

 points plotted are almost in line. The points at which the wave 

 passes through the base line, where the balance-pressure is zero, 

 correspond, if the protoplasm were free to flow, to the reversal 

 moments of the flowing direction. According to the concept generally 

 accepted, one rhythm involves the duration of time for a complete 

 progression and regression of the protoplasmic streaming (cf. Vouk 

 1910, 1913). Therefore, graphically, the distance on the base line 

 between alternating reversal points, including both + and — sides 

 of the wave, denotes, in a general sense, "one" complete rhythm. 

 Except for the wave groups at the beginning and at the end of the 

 wave train, the distances between any two adjacent maxima or adja- 

 cent minima have approximately constant intervals (periods) aver- 

 aging 93.7 seconds, and there is also mostly one point of inflexion 

 between the consecutive maximum and minimum of the curve. The 

 wave looks, on the whole, fairly regular and bears considerable 

 resemblance to the sinusoidal wave. 



The wave in Figure 6 does, however, show slight fluctuations, 

 which indicate that there is quantitatively no constant factor in 

 respect to amplitude, wave-form, etc. At the beginning and end of 

 the wave train, the amplitude diminishes conspicuously, and the 

 wave no longer sustains a regular form; whereas, in the middle part 

 of the train, the waves swell. When one considers the "envelope", 

 or imaginary margin, of this wave train, it assumes the form of a 

 long spindle, the middle portion of which is six times as wide as 

 the ends. 



It is extremely interesting to note that the change in amplitude 

 often takes place with considerable regularity, i. e., after a decreas- 

 ing amplitude period the wave swells out gradually to a maximum, 

 and after the lapse of a certain period of time, the magnitude 

 decreases again and is followed by the next increasing period. Fig- 

 ure 6 shows simply one long "waxing" period between two "waning" 



