EXPERIMENTAL IMITATION OF PROTOPLASMIC MOVEMENT. 101 



To prepare the vesiculate drops I proceed in the following 

 way : — lu a small agate mortar I grind a small quantity of 

 pure dry carbonate of potash (KgCOg) to a fine powder. I 

 then breathe on to the salt till it becomes slightly moist, and 

 with a glass rod add to it a drop of oil, mixing the two con- 

 stituents to a thickish paste. The success of the experiment 

 depends, however, more upon the nature of the oil than upon 

 the proportions of oil and salt in this mixture. Then with a 

 glass rod or a needle I place a few drops of the paste, about 

 the size of a pin's head or smaller, on a cover-glass, the corners 

 of which are supported by small pegs of soft paraffiue. I then 

 place on a slide a drop of water, and put the cover-glass over 

 this in such a manner that the drops of the paste are immersed 

 in the water, but are not much compressed, to which end 

 the corners of the cover- glass have been supported by the 

 paraffiue. The preparation is then placed in a damp chamber, 

 and remains there about twenty-four hours. The drops have 

 now a milk-white and opaque appearance. The preparation 

 is then well washed out with water by applying blotting- 

 paper to one edge of the cover-glass, and supplying water 

 at the other edge from a capillary tube. 



If the drops have turned out well, they will begin almost 

 immediately after this to move about rapidly, and change their 

 shape continuously. The water under the cover-glass must 

 now be displaced by glycerine, diluted with an equal bulk of 

 water, and the drops will then exhibit a vigorous streaming 

 and forward movement, becoming gradually quite transparent. 

 The amoeboid movements are generally more distinct if the 

 drops are somewhat compressed. If the drops do not show 

 the streaming movement you may succeed in producing it by 

 tapping the cover-glass slightly, by applying gentle pressure, 

 or sometimes by breaking up the drops. For it seems as if 

 at times incrustations were formed on the surface of the drops, 

 which prevent or impede the streaming movement, and which 

 can, in part at least, be removed by the above-mentioned 

 manipulations. 



It is especially interesting to see how fast and beautifully the 



