MOVEMENTS OF FOAM-DROPS 51 



account of this interval, I think I am not in error in 

 estimating it at some minutes. After complete union, an 

 entirely new centre of extension-currents is usually formed, 

 according to which the shape of the combined drop becomes 

 directed. 



If a drop in its forward movement comes towards one at 

 rest, or approaches a relatively quiescent spot in the margin of 

 a larger drop, the approach of its centre of stream lines calls 

 forth a corresponding streaming in the second drop also. 

 I shall go into the explanation of this phenomenon below. 



Larger drops usually form several or numerous centres 

 of extension - currents. In the accompanying Fig. 6 is 



Fig. 6. 



represented one of the finest examples of this kind which 

 came under my notice. The strongly pressed drop in 

 question had not less than eleven centres of streaming, 

 some of which had developed into long pseudopodium-like 

 processes. Such drops show, as was to be expected, no 

 actual forward movement as a whole ; on the other hand, the 

 actively streaming centres of the extension-currents usually 

 grow out like pseudopodia. Now since the streaming of 

 one or other of the centres frequently becomes gradually 

 slower and finally ceases, while, on the other hand, another 

 is developed more strongly, or even entirely new centres arise, 

 the result is that such drops show, as a rule, a striking 

 amoeboid change of form. In a relatively short time, after 



