STREAMING IN CELLS 81 



of streaming were essentially the same in all cells observed. 

 The contents always showed but a single centre of extension- 

 currents, situated, as a rule, at one end of the elongate cell, 

 more rarely, however, displaced slightly towards a lateral 

 wall, and very seldom occurring in the middle of one of the 

 longitudinal sides. Corresponding to this arrangement, the 

 axial current was, as a rule, directed longitudinally towards 

 the centre of extension, more rarely obliquely, and finally very 

 seldom transversely, to the long axis of the cell. In any 

 case the streaming was always a double-sided one, with a 

 flow on each side away from the centre of stream lines. 

 Nothing was ever observed of a rotational streaming, such as - 

 occurs so commonly in vegetable cells. I lay especial stress 

 upon this point, since I had hoped I might possibly have 

 seen something of the sort take place under the conditions 

 given. Isolated cases indeed, occurred where the current of 

 one side only passed a very short distance backwards, while 

 that of the other side ran round a larger part of the cir- 

 cumference of the contents. Although such a state of 

 things may be regarded as an approximation to rotation, 

 nevertheless I found, as has been stated, no proper rotational 

 streaming. It is not without interest to note that the 

 streaming in a large number of the cells was directed in 

 a similar sense ; yet here and there cells were seen with 

 the direction of the current reversed or different in some 

 other way. 



If therefore the experiments as yet performed cannot 

 be exactly said to have yielded great results, yet their 

 further continuation and modification might ultimately lead 

 to conclusions upon certain phenomena of protoplasmic 

 streaming in closed cells. It is easily understood that 

 conclusions are possible only to a limited extent in the ex- 

 periments described, since the conditions within the plant 

 cell are without doubt quite different, as will be described 

 with more detail in a later section. 



