THE ORIGINS OF MIND II5 



rest of the body. In these forms there are sometimes found 

 such sensory organs as eyespots. In the highest protozoa, the 

 Infusoria (the famous slipper animalcule, Parafnecium, is an 

 example) there are specialized fibrils which act as nerves and 

 which radiate from all parts of the tiny, microscopic body 

 to a center, which may be the first "brain" in the animal 

 kingdom. These fibrils are differentiated within the proto- 

 plasm of a single cell; they are not true nerves, but they can 

 and do give to these ciliated protozoa a surprisingly high 

 order of coordination, and a complexity of behavior we are 

 just beginning to appreciate. 



The basic behavior of Faramecium, as Jennings was able 

 to show, is "trial and error," and we see it in its simplest 

 form in this protozoan. It finds its way around a barrier or 

 avoids adverse conditions in its water habitat by backing 

 away, turning, going forward again, backing and turning 

 until it finds the solution. There is no apparent method in 

 the reaction. We find this trial-and-error method employed 

 all the way up the animal scale to man, although it becomes 

 less and less dominant. Even in man, however, as will be 

 brought out in Chapter 12, the method is employed in estab- 

 lishing childhood "learning sets," and later in life as well, 

 whenever experience is unable to cope with a situation. It is 

 the apparent method by which nature has solved the evolu- 

 tionary problems, and it is often the method of science. Jen- 

 nings was able to show that Faramecium does, of course, 

 show some positive reactions. Its bacterial prey is usually 

 found swarming together in raft-like collections of huge 

 numbers, and when the protozoan bumps into such a large 

 food supply it does not go through the usual avoiding reac- 

 tions. It stops and browses around the edges until satiated. 

 This is, apparently, not a reaction based entirely on the pres- 

 ence of food, since Faraineciinn will momentarily respond in 

 a similar way to roughened bits of paper or cotton. It reacts 

 to gravity, tending to swim upwards, where it browses over 

 floating particles. It gets its sense of up and down through 



