132 THE BEHAVIOR OF LOWER ORGANISMS. 



facts, with especial reference to these theories, seems, therefore, much 

 to be desired. The^ results of the present study will show, I believe, 

 that such a re-examination of the facts was greatly needed. 



As to the second object of this investigation, stated above, it is a 

 somewhat remarkable fact that the observational basis for a number of 

 the most important reactions assumed to exist in Amoeba is exceedingly 

 scanty, particularly so far as control of the direction of movement is 

 concerned. For example, one of the reactions most often assumed to 

 exist in Amoeba, and most commonly selected for imitation by 

 physical means, is chemotaxis, the movement toward or away from a 

 diffusing chemical. But no account exists, so far as I have been able 

 to discover, of actual observation of such a reaction in Amoeba, under 

 experimental conditions. Again, the effects of slight or of intense 

 localized mechanical stimuli, in controlling the direction of movement, 

 has not been worked out in detail. To fill these and similar gaps in 

 our knowledge, and to bring the different reactions into relation with 

 each other, so as to make possible a connected account of the behavior 

 of Amoeba, is, then, the second object of this paper. 



I shall first give an account of the movements and reactions of 

 Amoeba, as determined by observation and experiment, without enter- 

 ing in detail upon the theories of the subject. This will be followed 

 by a section dealing with the physical theories and physical imitations 

 of the movements and reactions, in the light of the facts set forth in the 

 first section. A brief final section will be devoted to a characterization 

 of the behavior of Amoeba from the standpoint of the student of 

 animal behavior. 



I am compelled to give a full description of the normal movements 

 of Amoeba, as the course of the investigation showed that the prevalent 

 conception of these movements, on which many of the theories have 

 been based, is not correct. 



DESCRIPTION OF THE MOVEMENTS AND REACTIONS. 



THE MOVEMENTS. 



MOVEMENTS OF AMCEBA AS DESCRIBED BY RHUMBLER AND BUTSCHLI J 

 AGREEMENT WITH CURRENTS IN A DROP OF FLUID MOVING AS A RE- 

 SULT OF LOCAL DECREASE IN SURFACE TENSION. 



There are few subjects that have been studied more than the nature 

 of the movements of Amoeba, but nothing final has been reached, even 

 from the descriptive standpoint. The first preliminary to an under- 

 standing of the nature of the movements must be to determine just what 

 movements take place. 



The most extensive recent study of the movements of Amoeba has 

 been made by Rhumbler (1898), though the magnificent monograph of 



