Organic Connection Between Physical and Psychical 253 



significance. But this latter type of activity, wholly di- 

 vorced from a direct-orienting reaction, and even from a 

 bilateral body symmetry, is of wide application among the 

 lower animals. It was first brought clearly to the atten- 

 tion of biologists by Jennings in his now well-known inves- 

 tigations on Paramecium and other protozoans. These in- 

 vestigations formed the bases of the "avoiding reaction" and 

 the "trial and error" conceptions now generally recognized 

 to be of much importance in the behavior of all animals, es- 

 pecially of those in which a high measure of bodily activity 

 occurs but in which there is little or no intelligence. Jen- 

 nings' lucid account of his results in the chapter Be- 

 havior of the Infusoria; Paramecium (Behavior of Lower 

 Organisms) is strongly commended to the reader. 



The following paragraph must suffice for our reference 

 to this work. After describing the behavior of Parame- 

 cium, Jennings writes : "This method of behaving is per- 

 haps as effective a plan for meeting all sorts of conditions as 

 could be devised for so simple a creature. On getting into 

 difficulties the animal retraces its course for a distance, then 

 tries going ahead in various directions, till it finds one in 

 which there is no further ^ obstacle to its progress. In this 

 direction it continues. Through systematically testing the 

 surroundings, by swinging the anterior end in a circle, and 

 through performing the entire reaction repeatedly, the in- 

 fusorian is bound in time to find any existing egress from 

 the difficulties, even though it be but a narrow and tortuous 

 passageway." And this complex and highly useful be- 

 havior is performed by an organism which, so far as the 

 best anatomical researches have been able to determine, is 

 entirely devoid of a nervous system, and consists of a single 

 cell! 



But the "trial and error" scheme here exemplified is by 

 no means confined to unicellular, non-nervous animals, nor 

 to experimentally produced conditions. That it is opera- 



