138 evolution: the ages and tomorrow 



transitional forms, and practically all are still represented by 

 living animals. 



The earliest hypothetical origins of the first stage go back 

 to inanimate matter. We have already reviewed the evolu- 

 tion of the living from the nonliving and have found that it 

 is possible to picture a continuous synthesis from the sim- 

 plest chemical compounds to the enormously complex con- 

 figurations of the earliest living entities, such as the genes. 

 There is, however, no clear line of biological demarcation 

 between animate and inanimate. The same is apparently 

 true in the behavior phase. Biologists begin to pick up di- 

 rect information on the behavior of living organisms at the 

 precellular level of viruses and genes and find a gradual rise 

 in the capacity of response through primitive bacteria to 

 unicellular animals. 



Faramecium is well within the first stage in the evolution 

 of behavior, and it might be of interest to review some of 

 the capacities of life at this level. The external world to this 

 microscopic organism is a series of formless stimuli, prob- 

 ably much like the stimulus of smell is to us. Faramecium^ s 

 world is only very vaguely a world of objects, not "round 

 and firm and fully packed," but rather of individually sep- 

 arate stimuli which do not give it a clear sense of "things" 

 and probably very little sense of space. To it, time is ex- 

 tremely limited; but, since it does have a vague capacity for 

 learning (see Chap. 9), the past is not entirely blotted out 

 in the narrow present in which it lives. 



The first stage in the evolution of behavior is, then, a 

 nearly timeless, spaceless world of stiinuli, with just the be- 

 ginnings of the capacity for perceiving two stimuli united 

 into one experience, such as "seeing" an object as round 

 and hard. It is a dim world, but one is justified in describing 

 it as "not without some degree of consciousness." Most of 

 the lower animals are at this level, and some, notably the 

 jelly fishes, have been shown to have some capacities for 

 learning (see Chap. 10). Learning means profiting by ex- 



