46 The Animal Mind 



pletely again, and started away." The small Amoeba con- 

 tracted into a ball and remained quiet until through the move- 

 ments of the large one there chanced to be but a thin layer 

 of protoplasm covering it. This it rapidly pushed through, 

 escaped completely, and was not pursued by the large Amoeba 

 (211, pp. 17-18), (Fig. 3). 



Of this performance Jennings says, "It is difficult to con- 

 ceive each phase of action of the pursuer to be completely 

 determined by a simple present stimulus. For example . . . 

 after Amoeba b has escaped completely and is quite separate 

 from Amoeba c, the latter reverses its course and recaptures 

 b. What determines the behavior of c at this point ? If we 

 can imagine all the external physical and chemical conditions 

 to remain the same, with the two Amoebae in the same relative 

 positions, but suppose at the same time that Amoeba c has 

 never had the experience of possessing b } would its action 

 be the same? Would it reverse its movement, take in b, 

 then return on its former course ? One who sees the behavior 

 as it occurs can hardly resist the conviction that the action at 

 this point is partly determined by the change in c due to the 

 former possession of b, so that the behavior is not purely 

 reflex" (211, p. 24). 



If it is true that an Amoeba which had not just u had the 

 experience of possessing 6" would not have reversed its move- 

 ment and gone after b when the latter escaped, still we cannot 

 think it possible that c's movements in so doing were guided 

 by a memory image of b. It may be supposed that the recent 

 stimulation of contact with b had left a part of c's protoplasm 

 in a condition of heightened excitability, so that the weak 

 stimulus offered perhaps by slight water disturbances due 

 to b's movements after escaping produced a positive reaction, 

 although under other circumstances no reaction would have 

 been possible. In any case, there is no evidence that Amoeba's 



