The Mind of the Simplest Animals 55 



mecium than in Amoeba, there is rather less possibility of 

 variety in the conscious experience of the ciliated protozoon. 

 The reversal of cilia, the rolling toward the aboral side, 

 form a more elaborated and specialized mode of withdrawal 

 than does the simple checking of protoplasmic flow at one 

 region of the body. But, supposing Paramecium to be con- 

 scious, the significance for its consciousness of the negative 

 or avoiding reaction is even less clear than that of the corre- 

 sponding behavior in Amoeba. The negative reaction in 

 Amoeba is contrasted on the one hand with a positive reaction, 

 opposite in character, given to stimuli of less intensity, so that 

 the opposition of unpleasantness and pleasantness in the 

 human mind is clearly suggested ; and on the other hand with 

 a food-taking reaction, given to edible substances, and hinting 

 at a differentiation corresponding to that between touch and 

 taste in our own experience. The only approach to a positive 

 reaction in Paramecium is the coming to rest in contact with 

 solids, and this does not present any very striking analogy 

 with such expressions of pleasantness as we are acquainted 

 with. Further, Paramecium has no special food-taking 

 reaction at all. The fact seems to be that its greater speed of 

 motion has developed its negative reaction at the expense of 

 the others. It does not need to reach out in a typical positive 

 reaction, for its rapid dashing through the water greatly 

 increases its natural chance of getting food. The whirling 

 of the oral cilia brings it edible as well as inedible substances. 

 It does, however, much need in its headlong career a means 

 of avoiding the dangers into which it may rush, and so we 

 find the very definite and well-adapted negative reaction 

 dominating the field. If, then, the mind of an Amoeba is 

 thought of as capable of three or four qualitatively different 

 experiences, that of a Paramecium must be even less 

 favored. 



