48 The Animal Mind 



all other animals, the power of "getting used" to certain 

 forms of stimulation, so that on long continuance they cease 

 to provoke reaction. "Thus," Jennings says, "Amoebae 

 react negatively to tap water or to water from a foreign 

 culture, but after transference to such water they behave 

 normally" (378, p. 20). Such cessation of reaction occurs 

 when the continued stimulus is not harmful. In a sense, 

 it may be called an effect of experience ; but there is clearly 

 no reason for supposing that it involves the revival of 

 experience in the form of an idea or image. We have 

 parallel phenomena in our own mental life. A continued 

 stimulus ceases to be "noticed," but the process involves 

 rather the disappearance of consciousness than the appear- 

 ance of a memory image. Jennings, however, is inclined 

 to think that preceding stimulation may modify the 

 Amoeba's behavior in a way more nearly suggesting memory 

 in a higher type of mind. He describes an interesting 

 observation to illustrate this. A large Amoeba, c, had 

 swallowed a smaller one, , but had left a small canal 

 open, through which the swallowed one made efforts to 

 escape, which were several times foiled by movements on 

 the part of the large Amoeba toward surrounding it again. 

 Finally it succeeded in getting completely out, whereupon 

 the large Amoeba "reversed its course, overtook b, engulfed 

 it completely again, and started away." The small Amoeba 

 contracted into a ball and remained quiet until through the 

 movements 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 (378, pp. 17-18), (Fig. 3). 



Of this performance Jennings says: "It is difficult to 

 conceive each phase of action of the pursuer to be completely 

 determined by a simple present stimulus. For example 



