284 BEHAVIOR OF THE LOWER ORGANISMS 



normal condition of Paramecium is an active one, with its cilia in rapid 

 motion ; it is only under special conditions that it can be brought partly 

 to rest. Vorticella, as Hodge and Aikins (1895) showed, is at all times 

 active, never resting. The same is true of most other infusoria and, in 

 perhaps a less marked degree, of many other organisms. Even if external 

 movements are suspended at times, internal activities continue. The 

 organism is activity, and its activities may be spontaneous, so far as 

 present external stimuli are concerned. 



The spontaneous activity, of course, depends finally on external 

 conditions, in the same sense that the existence of the organism depends 

 on external conditions. The movements are undoubtedly the expression 

 of energy derived from metabolism. The organism continually takes 

 in energy with its food and in other ways, and continually gives off 

 this energy in activities of various sorts. The point of importance is 

 that this activity often depends more largely on the past external 

 conditions through which the energy was stored up than upon present 

 ones. Thus the organism may move without the present action of 

 anything that may be pointed out as a specific external stimulus to 

 this movement. 



This fact is of great importance for understanding behavior, and 

 many errors have arisen from its neglect. If we see an organism moving, 

 it is not necessary to assume that some external stimulus now acting is 

 producing this movement. In studying the reactions to present particu- 

 lar stimuli, as light or gravity or a chemical, it is in many cases not 

 necessary to account for the fact of movement, for the movement comes 

 from the discharge of internal energy, and often the organism was moving 

 (though perhaps in another direction) before the stimulus began to act. 

 It is only the change in the movement when the stimulus acts that the 

 present stimulus must account for. In the movement of Paramecium 

 toward the cathode, it is not necessary to assume, as some have done, 

 that a special force (as cataphoric action) is required, to carry the ani- 

 mals. They were moving equally before the electric current began to 

 act; the difference that the stimulus has made is in the direction of 

 motion, and it is only this that the stimulus must account for. In the 

 movements of infusoria toward chemicals, some have supposed that an 

 attractive force from the chemical was necessary, actually bearing the 

 organisms along; this is quite superfluous. In general, when an 

 organism moves toward or away from any agent, it is unnecessary to 

 assume that an actually attractive or repellent transporting force' is act- 

 ing upon it. Often — perhaps usually in the lower organisms — move- 

 ment in a certain direction is due only to the release of inhibition. The 

 organism moves in the given direction because it is moving from internal 



