THE MOVEMENTS AND REACTIONS OF AMCEBA. 



INTRODUCTION: OBJECTS OF THE INVESTIGATION. 



The present paper contains the results of an investigation which was 

 undertaken with two general problems in mind. The first purpose 

 was to determine by observation and experiment, from the standpoint 

 of the student of animal behavior, how far recent physical and 

 mechanical theories go in aiding us to explain the behavior of Amoeba. 

 The second object of the work was to furnish needed additional data 

 on the reactions of Amoeba to stimuli, and to systematize and unify 

 our knowledge of its behavior. 



The recent theories which would resolve the activities of Amoeba 

 largely into phenomena due to alterations in the surface tension of a 

 complex fluid seem to promise much. They are of preciselv the 

 character from which most may be hoped ; from a study of the physics 

 of matter in a state similar to that found in the living substance, the 

 laws of action of this living substance are sought. Such theories have 

 been developed, as is well known, by Berthold (iSS6), Qiiincke 

 (iSSS), Biitschli (1892), Verworn (1892), Rhumbler (189S), Bern- 

 stein (1900), Jensen (1901), and others. The success of this method 

 of attacking the problems seems great. Activities similar, at least 

 externally, to those of Amoeba, are produced by physical means, and 

 fully analyzed from the physical and mechanical standpoint. In this 

 manner the movement, the control of movement by external agents, 

 the feeding, the choice of food, the making of the shell, and other 

 features of the behavior have been more or less closely imitated,* and 

 in a way permitting a complete analysis in accordance with chemical 

 and physical laws. 



From the standpoint of the student of animal behavior, the resolu- 

 tion of the behavior of any organism into the action of known physical 

 laws must be a matter of the deepest interest. The actions of higher 

 organisms seem at present so far from such a resolution that some 

 investigators believe an essential ditl'erence in principle to exist 

 between the behavior of living things and non-living things ; between 

 the laws of biology and those of physics. The resolution, then, of the 

 behavior of even the simplest organism into known physical factors 

 would be an event of capital significance, affecting fundamentally the 

 whole theory of animal behavior. A renewed thorough study of the 



♦See especially Rhumbler, 1898. 131 



