286 The Animal Mind 



facts about Paramecium. "If the animal is at rest against 

 a mass of vegetable matter or a bit of paper, . . . 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 strong 

 blow on the anterior end causes the animal to leave the solid 

 and give the typical avoiding reaction." "If specimens 

 showing the contact reaction are heated, it is found that they 

 do not react to the heat until a higher temperature is reached 

 than that necessary to cause a definite reaction in free-swim- 

 ming specimens." "On the other hand, both heat and cold 

 interfere with the contact reaction. Paramecia much above 

 or much below the usual temperature do not settle against 

 solids with which they come in contact, but respond in- 

 stead by a pronounced avoiding reaction." "Specimens in 

 contact with a solid react less readily to chemicals than do free 

 specimens. . . . On the other hand, immersion in strong 

 chemicals prevents the positive contact reaction." "The 

 contact reaction may completely prevent the reaction to 

 gravity," and to water currents. It also modifies the reaction 

 to the electric current. While a part of the influence exerted 

 by the contact reaction on other responses may be purely 

 physical, due to the fact that an actual secretion of mucus 

 may occur whereby the animal "sticks fast" to the solid, 

 yet this alone does not explain the facts, for the cilia that are 

 not attached do not behave normally. The reaction to gravity 

 regularly yields whenever opposed to the action of any other 

 stimulus (211, pp. 92 ff.). 



Sometimes the action of one form of stimulation merely 

 affects the form of the response to another, as in the case where 

 abnormal temperature causes the avoiding instead of the 

 positive reaction to be given to solids. In other cases, re- 

 action to one of the stimuli is suppressed or weakened. The 

 facts suggest that the influential stimulus is either the ont 



