The Mind of the Simplest Animals 49 



Amoeba may not be a continuous stream at all. Since its 

 sensitiveness to changes in its environment is less developed 

 than that of a human being, and there are no trains of ideas 

 to fill up possible intervals between the occurrences of out- 

 side stimulation, the Amoeba's conscious experience may be^v 

 rather a series of " flashes" than a steady stream. And for 7 

 the Amoeba, again, we must remember that even such a series 

 would not exist as such ; the perception of a series would involve 

 the revival of its past members. Each moment of conscious- 

 ness is as if there were no world beyond, before, and after it. 

 Another consequence of that simplicity of structure which 

 results both from the rudimentary powers of sensory discrimi- 

 nation and from the absence of memory ideas in the Amoeba's 

 mind is that there can be no distinction, within a given mental 

 process, between that which is attended to and that which is 

 not attended to, between the focus and the margin of conscious- 

 ness. Given a consciousness which at a certain moment is 

 composed of the qualitatively different elements A, B, C, and 

 D, we can understand what is meant by saying that A is 

 attended to, is in the foreground of attention, while B, C, 

 and D remain in the background. But given, on the other 

 hand, a creature whose conscious content at a certain time 

 consists wholly of the qualitatively simple experience A, it 

 is evident that attention and inattention are meaningless 

 terms. Different moments of its consciousness may differ 

 in intensity; but attention, involving, as it does, clearness 

 rather than intensity, arises only when mental states have 

 become complex and possess detail and variety within their 

 structure. 



10. The Structure and Behavior of Paramecium 



Although Amoeba represents in structure the simplest form 

 of animal life, its behavior in response to stimulation is rather 



