THE BEHAVIOR OF INFUSORIA; PARAMECIUM 109 



conditions, and retention of others. It may be characterized briefly 

 as a selection from among the varied conditions brought about by varied 

 movements. 



The fundamental question for this method of behavior is, Why does 

 the organism reject certain conditions and retain others? We find 

 that the animal rejects, on the whole, such things as are injurious to it, 

 and accepts those that are beneficial. There are perhaps some excep- 

 tions to this, but these are rare and only noticeable because exceptional ; 

 in a general view the relation of rejection and acceptance to injury and 

 benefit is evident. It results in keeping the animals from entering 

 temperatures that are above or below those favorable for the life pro- 

 cesses, in causing them to avoid injurious chemicals of all sorts, in saving 

 them from mechanical injuries, and in keeping them in regions con- 

 taining food and oxygen. Clearly, the animal rejects injurious things, 

 and accepts those that are beneficial. 



How does this happen? We meet here the same question that we 

 find in higher organisms and man. How does it happen that in man 

 the response to heat and cold beyond the optimum is by drawing back, 

 just as it is in Paramecium? How does it happen that in both cases 

 there is a tendency to reject things injurious and retain things bene- 

 ficial ? We shal^ attempt in a later chapter to bring out the relations 

 involved in this problem, in such a way as to make it possibly a little 

 more intelligible; here we shall content ourselves with pointing out 

 the identity of the problem in the infusorian and in man. 



LITERATURE VI 



A. Interference between contact and other stimuli: PUTTER, 1900; JENNINGS, 

 1897, 1904 h. 



B. Heat and other stimuli : MENDELSSOHN, 1902 a; MASSART, 1901 a. 



C. Gravity and other stimuli : SOSNOWSK 1 , 1 899 ; MOORE, 1903. 



D. Behavior in conjugation : JENNINGS, 1904^; BALBIANI, 1861. 



