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
'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

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