62 DEVELOPMENT AND PURPOSE CHAP. 



organisms are in some degree capable. This accommoda- 

 tion, which of course is familiar in manifold directions in 

 our own life, is also observable among Protozoa. Para- 

 mecium introduced into a weak salt solution will give the 

 c avoiding reaction,' and repeat it many times, but finally 

 abandon it. If not killed by the new medium, that is to 

 say, the animal becomes acclimatised. The efforts to escape 

 cease, and it resumes its normal life. Often, as we know, 

 acclimatisation will lead us to prefer the accustomed condi- 

 tion to that which originally suited us. In such cases 

 there is a certain correlation based on past experience. But 

 it is to be carefully distinguished from the correlation of 

 actions, e.g. of means leading to some end. What it 

 involves is a shifting of the equilibrium point, by which so 

 many acts of the animal are governed. This point is 

 adapted to the conditions under which the individual lives, 

 and with this adaptation a whole attendant series of actions 

 is, of course, modified accordingly. We might speak of 

 acclimatisation as a correlation of the equilibrium point 

 with the persistent conditions given in the experience of 

 the individual. 



(3) Inarticulate Correlation, (a) Selective modification. 



The teaching of experience and the development of mind 

 which is stimulated by it, if not founded on it, has as its 

 unit a relation between two data affecting the organism. 

 When we speak of learning by experience, or regard 

 thought as resting on experience, this is the kind of experi- 

 ence that we mean, and when we trace the growth of intel- 

 ligence, what we have essentially to consider is the way in 

 which the mind apprehends or at lowest is affected by 

 data in their relations, the kind of data that it can 

 apprehend, and the use that it makes of them when 

 grasped. 



Probably the earliest form in which such relations affect 

 conduct is one which is amply verified for certain Infusoria. 

 A stentor gently touched on one side will contract upon its 

 stalk, but will soon open out again. Touched once more, 

 it will perhaps bend to one side, and if continually molested 

 in this manner, it will uproot itself in pardonable dudgeon 



