52 PROTOPLASM 



half an hour or an hour, a drop of this kind has altered 

 its shape very considerably. That drops of such large 

 size when under strong pressure move but little for- 

 wards as a whole, may partly depend also 011 the fact that, 

 having relatively large surfaces of contact with the cover 

 glass and slide, they meet with a proportionately large 

 resistance from friction. When a single one of their pseudo- 

 podial processes streams strongly forwards, as, for example, 

 the one denoted by 6 on Fig. 6, it may happen that, as it 

 continually grows farther out, without being followed by 

 the principal mass of the drop, it finally breaks off from the 

 latter, owing to the bridge connecting it with the main body 

 becoming more and more attenuated, until it breaks. 

 In this way the process mentioned, denoted by b in 

 Fig. 6, separated off soon after the drawing was fin- 

 ished, and then moved on as an independent drop in the 

 direction of its centre of extension-currents. Similar pheno- 

 mena of division, if it be wished to so term this case, have 

 often been observed by me in a similar manner. 



It is frequently seen that a strongly streaming centre 

 of extension -currents gradually suppresses a neighbouring 

 weaker one. One of the lateral streams from the first 

 centre gradually overcomes the opposing current of the 

 latter, and thus finally brings by degrees the whole centre 

 to extinction. 



Continuance of the Streaming Movements 



Successfully manufactured drops show the described 

 phenomena of streaming for at least twenty -four hours, dur- 

 ing which time the streams gradually become weaker and 

 weaker, and finally cease. Frequently, however, I could follow 

 them for from forty-eight hours to three days. Finally, in May 

 1889, after several attempts, an oil was successfully combined, 

 which yielded drops of peculiarly good streaming powers. In 

 one of the preparations the largest drop of froth, made from 

 this oil on 28th May, still streamed distinctly, though 

 feebly, on the 3rd of June, so that in six days it had not 

 completely come to rest. 



