174 life's beginning on the earth 



cemented together. These particles are fitted together accurately in a 

 single layer, so that no crevices can be discovered. How are these delicate 

 houses built? It would seem that the process must require much care, 

 skill, and intelligence, to select the proper pieces and put them together 

 with such nicety that the shell is but a single layer thick, and yet no gaps 

 are left. 



But the drop of chloroform is not to be outdone, and under the proper 

 conditions will produce a shell not inferior to that of Difflugia. This may 

 be shown very simply. Chloroform is rubbed up with fragments of glass 

 in a mortar until the glass is reduced to the finest dust. Then, with a 

 pipette drawn out to a small point, drops of this mixture of chloroform and 

 glass dust are injected into water. At once the grains of glass come to the 

 surface of the drops so formed and arrange themselves there in a single 

 layer, without chinks or crevices, exactly as in the shell of Difflugia. The 

 chloroform drop is covered with a shell of a delicacy and beauty equal to 

 that of Difflugia, and almost indistinguishable in texture from it. Some of 

 these artificial shells, if unexpectedly found with the microscope, would 

 certainly be taken for those of Difflugia. . . In place of chloroform, linseed 

 oil or other oil may be used. They must be injected into 70 per cent alco- 

 hol, since the oil would float upon water. The process is exactly the same 

 as when chloroform is used. 



4. OIL-DROPS EXTRACTED FROM THE BRAIN OF FRESHLY 



KILLED ANIMALS 



All these experiments demonstrate the close approxima- 

 tion of the behavior of the most primitive animals and a 

 simple oil-drop. Who would suppose that the mysteries 

 of life are capable of such simple explanation? Where is 

 the vital force if an oil-drop can move about, select its 

 food, devour it, and organize itself in very much the same 

 manner as the simplest animal? 



Apparently forces similar to those acting in plain oil- 

 drops are responsible for the movement of Amoeba. But 

 what forces act in the more highly developed animals? The 

 working of a muscle cannot be so readily matched by the 

 behavior of an oil-drop. Must we resort to an assumption 

 of vital forces in this case? 



Obviously the application of the term, vital force, is 

 arbitrary. Before the similarity of the oil-drop to the 

 Amoeba was recognized, all the movements of Amoeba 



