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- 



