CHAPTER VI 



BEHAVIOR OF PARAMECIUM {Continued) 



Behavior under Two or More Stimuli ; Variability of Be- 

 havior ; Fission and Conjugation ; Daily Life ; General 

 Features of the Behavior 



i. behavior under two or more stimuli 



The behavior thus far described is that which takes place under the 

 influence of but a single kind of stimulation. But normally the condi- 

 tions are as a rule more complex than this ; the animal is affected by 

 several sets of stimuli at once. What is the behavior under such condi- 

 tions ? If, while the Paramecium is reacting to the stimulus a, the stim- 

 ulus b acts upon it, will it react in the usual way to b ? Or will it con- 

 tinue to react to a? Or will its action form a compromise between the 

 usual reactions to the two agents? Or will it, finally, react in a new 

 way, different from the usual reactions to either a or b ? 



Let us examine first the behavior under the simultaneous action of 

 the contact stimulus and of other usual stimuli. As we have seen, the 

 contact stimulus often causes the animal to come to rest and behave in 

 a characteristic manner, while other classes of stimuli usually induce 

 the avoiding reaction or a movement forward. Thus opposite reactions 

 are induced by the two kinds of stimuli acting separately. What will be 

 the result when the two act together? 



If the animal is at rest against a mass of vegetable matter or a bit of 

 paper under the action of the contact stimulus, and it is then struck 

 with the tip of a glass rod, we find that at first it may not react to the 

 latter stimulus at all. A touch that would cause a free swimming speci- 

 men to give the avoiding reaction in a pronounced way often has no evi- 

 dent effect on the quiet specimen. Sometimes, however, a touch coming 

 from behind causes the animal to move forward, still remaining in con- 

 tact with the solid object ; it thus creeps a short distance over the sur- 

 face of the solid. Finally, a strong blow on the anterior end causes the 

 animal to leave the solid and give the typical avoiding reaction. 



Thus we find that under the simultaneous action of the two stimuli 



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