382 



THE MAINTENANCE OF THE INDIVIDUAL 



behavior according to the stimulus pattern it receives. This modi- 

 fication results in a change or tension on the part of the organism, 

 leading it toward a goal. This goal may be food, or some other 

 "desirable" situation. Many experiments have been made which 

 indicate that modifications of behavior which result in learning take 

 place very early in the animal scale. Schaeffer ^ made an interesting 

 experiment with Ameba. He put a particle of glass close to an 

 Ameba that had been starved for some time, making the glass vibrate 

 by means of a rod. The Ameba immediately surrounded the glass, 

 forming a food vacuole, but after six minutes expelled the glass. 

 Five minutes later the glass was again presented, and again the 

 Ameba ingested it, this time expeUing the glass after three and a half 

 minutes. In a third presentation the glass was only partially ingested 

 and two more trials gave slight food response. All further trials 

 showed the Ameba completely indifferent to the glass. This con- 

 tinued placing of nonedible material in front of the animal set up a 

 tension in the protoplasm which resulted in a modified behavior, 

 causing indifference to the vibrating glass. 



In animals which have only a nerve net, modification of behavior is 

 also possible. In the famous experiments of Loeb and of Parker bits 



of meat were presented 

 to the tentacles of a sea 

 anemone, the meat being 

 passed by the tentacles 

 into the mouth. Then 

 the same tentacles were 

 fed with bits of filter 

 paper which had been 

 soaked in beef juice. At 

 first the animal made no 

 distinction between food 

 and filter paper but after 

 ten trials learned that 

 filter paper was not food and constantly rejected it. Hundreds of 

 other examples might be given to show that behaviors are modifiable. 

 But if lower animals live in a world of present actions and "have no 

 thought for the morrow," then it is doubtful if this conditioning of 

 behavior means much in the ultimate solution of their life problems. 



meat 



filter papei~ N/ilb meat jui<ie, 

 is token , , 



taken to 

 mouth 



popct- is rejecteoC 



A sea anemone will learn to distinguish between 

 meat and filter paper flavored by meat juice. 



1 Schaeffer, A. A., "Choice of Food in Amoeba." Journal of Animal Behavior, 1917, Vol. VII, 

 220-252. 



