160U Journal of Applied Microscopy 



hold of the piece of shellac again with the forceps and draw it away, the chloro- 

 form drop stretches out after it, and lets go of it only with the greatest apparent 

 reluctance. If allowed to retain the bit of shellac, it proceeds slowly to dissolve 

 it, — just as the Amoeba proceeds to digest the substance which it has taken 

 within itself. A second and third piece of shellac will be accepted with the same 

 avidity as the first. 



Other substances may be offered to the chloroform drop. Glass, sand, dirt, 

 wood, grass, gum arable, and chlorate of potash, for examples, are rejected ; 

 shellac, paraffin, styrax, hard Canada balsam, and various other substances are 

 accepted. 



It thus appears that a drop of chloroform exercises choice in determining 

 what substances shall be taken into itself, fully as decidedly as Amoeba does. 

 The same is true of other fluids, of whatever sort. We must then throw out 

 completely the power of choice of food as any test of mental power or even of 

 life. Amoeba merely shares this power with all other masses of fluid. It is a 

 suggestive fact, and one which has possibly a deep significance, that the chloro- 

 form drop (or other fluid) tends to take into itself especially such substances as 

 will dissolve within it, or have a chemical affinity for it, just as Amoeba tends 

 to take within itself substances which it can digest. 



The power of choice in inorganic fluids is bound up with the phenomena of 

 solubility and surface tension, which cannot be discussed here. 



These experiments on the power of choice in fluids are due to Rhumbler. 

 There is absolutely no technical difficulty in performing them, and they are 

 exceedingly striking and instructive. 



4. Other Activities Connected 7i.<ith the Taking of Food. The method by which 

 Amoeba takes a small particle of food is very similar to that by which the chlo- 

 roform drop takes within itself a bit of gum shellac. The protoplasm simply 

 flows over and envelops the food particle. But at times the problem presented 

 to the Amoeba if food is to be obtained is much more difficult. Sometimes the 

 food available is in the form of a long thread of Alga, many times the length of 

 the Amoeba. How is such an awkward piece of material to be managed ? There 

 seem to be only two possibilities for getting such a long thread into a short 

 Amoeba. One is to cut it into lengths, the other to coil it up. Amoeba has no 

 teeth for cutting up the thread, so it adopts the plan of coiling it. Individuals 

 engaged in this process are sometimes found among the specimens studied in the 

 laboratory ; the process has been described in detail by Rhumbler. 



The Amoeba first settles itself upon the filament somewhere in its length, and 

 envelops a portion of it. It stretches out a slight distance along the thread, then 

 bends over, of course bending the filament at the same time. The bending is 

 continued until there is a loop formed within the Amoeba. The animal now 

 continues to stretch out along the two ends and to bend them over, till the loop 

 is doubled, tripled, and a coil is in process of formation. This is continued until 

 the entire filament is rolled up into a neat little coil within the Amoeba, where it 

 is digested. 



What are we to say to such a clever solution of a somewhat difficult problem 

 as we have here ? Must we admit to Amoeba the power of grasping a situation 



