CHAPTER VII 

 THE BEHAVIOR OF OTHER INFUSORIA 



Action Systems. Reactions to Contact, to Chemicals, to Heat 



and Cold 



The infusoria form a large and varied group of organisms. In 

 the present chapter we shall try to show how far the behavior of Para- 

 mecium is typical for the group, and to bring out important differences 

 found in the behavior of other species. Certain features of behavior 

 are better illustrated in other infusoria than in Paramecium ; these we 

 shall treat in detail. This is notably true of the reactions to light, and 

 to a less degree of the reactions to certain other stimuli. Certain 

 infusoria are much more favorable for a study of the modifiability of 

 reactions than . Paramecium, so that we shall examine these relations 

 with care. 



I. THE ACTION SYSTEM 



We found that Paramecium has a certain set of ways of acting, — 

 of "habits," one might call them, — of which its behavior under most 

 conditions is made up. These are few in number and combined into 

 a connected system, which we have called the "action system." The 

 action system of Paramecium is typical of what we find throughout the 

 infusoria, including both the flagellates and the ciliates. But it becomes 

 modified among different species, in accordance with their varying 

 structure and the conditions under which they live. Practically all the 

 infusoria agree with Paramecium in swimming in a spiral when passing 

 freely through the water, and in the fact that when stimulated they 

 turn toward a certain side, defined by the structure of the organism. 

 But some species instead of swimming freely usually creep along sur- 

 faces, while others are attached by one end to solid objects, remaining 

 in the same spot indefinitely. These different methods of life neces- 

 sitate changes in the action system. We shall take up briefly a number 

 of species, bringing out the essential features of the action system. 



no 



