iv MENTAL DEVELOPMENT 51 



II. CORRELATION BY CO-EXISTENT CONDITIONS. 

 (i) Equilibration. 



It would however give a false impression of the opera- 

 tion of either form of type-reaction to speak of them 

 without qualification as unvarying. In both relations we 

 constantly find that the condition of the organism, concomi- 

 tant stimuli and the relation of the organism to other things 

 have their effect, controlling, limiting, possibly suppressing 

 a reaction or adjusting one type-reaction to another in 

 a combination or a series by which a certain result is 

 obtained. For instance, an infusorian as it swims en- 

 counters alkaline matter. It starts back a little way, 

 reversing the movement of its cilia. This may be taken 

 as a reflex. But it is succeeded by a typical exploratory 

 motion which ends in the animal's moving forward at a 

 different angle. If the new motion again brings it into 

 contact with the alkali the process is repeated and it con- 

 tinues until a direction is reached which takes it from the 

 alkali altogether, when these reactions cease and the 

 ordinary forward movement proceeds. Putting many such 

 instances together we may say that there is for the organism 

 a certain condition in which its ordinary structural activities 

 go equably forward. Any disturbance of their equilibrium 

 is a stimulus to reactions which continue until the equili- 

 brium is restored. This may be achieved by a normal 

 sequence of reactions, but if not there will be some varia- 

 tion from the normal, perhaps some suitable modification, 

 perhaps merely heightened and continued activity con- 

 tinued that is, until the disturbance begins to paralyse the 

 powers of the organism. In higher stages we recognise 

 this condition without ambiguity as one of effort. At 

 lowest, we must regard it as one in which the co-present 

 organic conditions modify the type-reactions, repeating or 

 combining them in such ways as remove a disturbance. 

 The action tending to remove the trouble is chosen out of 

 many possibilities, and if it does not succeed the animal 

 persists till relief is obtained. On the other hand, as soon 

 as equilibrium is gained the " efforts " cease, and the normal 



