54 PROTOPLASM 



to rest, begin to stream anew with heating, or that such 

 drops as were unwilling to stream well succeed in doing so 

 with a higher temperature. When several centres of stream- 

 ing are present, the drops show a rapid change of form, ac- 

 companied by the appearance of new centres and the dis- 

 appearance of earlier ones. An astonishing case of this kind 

 is figured by me in the accompanying Fig. 7 ; the period 

 of time in which the amoeboid change of form depicted 

 took place was not more than about ten minutes. 



I was unable to ascertain any influence exerted by gravity on 

 the streaming movements. Preparations with streaming, and 

 usually somewhat strongly compressed drops, were placed verti- 

 cally by bending the microscope back, and observed for some 

 time in this position. The streamings appeared, however, to be 

 in no way distinctly influenced, and took place equally well 

 both in the direction of gravity as well as against it, or in any 

 other direction. Although these experiments are not free from 

 objection, yet I wished to mention them briefly. 



I also instituted some experiments to determine the possi- 

 bility of any influence of light on the processes of movement. 

 These experiments were performed with drops that were not 

 pressed and which were in glycerine. The preparations were 

 placed near the window on a piece of black paper, and in ad- 

 dition the half of the preparation turned away from the window 

 was covered with black paper in such a way that at least one 

 of the drops was just half covered by the paper. Over the pre- 

 paration a glass vessel was then placed, of which the half turned 

 away from the window was covered by a black cloth. The few 

 experiments carried out up till now have shown no influence of 

 light. The drops sometimes wander into the light, sometimes 

 into the dark, most frequently the former. It was certainly 

 striking that for the most part their movements were more or 

 less in the direction of the light that reached them, i.e. either 

 towards the window or away from it ; but this result may also 

 be only a matter of chance, on account of the number of experi- 

 ments being too small to establish it. 



Reaction of the Drops of Foam to Electricity 



Since it seemed to me from the outset very important to 

 investigate the influence of electric forces on the phenomena 

 of streaming movement in the drops of foam, I have occupied 





