So far we have considered correlation dependent on the
hereditary structure, or on the operation of present, i.e.
co-existent conditions. We have now to deal with correla-
tions arising directly or indirectly out of the past experi-
ence of the individual, and related to his future, perhaps his
remote future, or to that of his society.

(1) Enduring organic effects.

Now the influence of past experience in a certain sense
affects action at a very early stage. For the reaction of the
organism is, of course, dependent on the organic condition
at the moment, and this condition will be affected by the
past. Thus the animal which has just had a full meal will
in general (not always) react to food in a very different way
from the animal which is hungry. Again, the animal
which has begun to chase a prey has its faculties and im-
pulses directed towards that prey in a special manner, and
it may, in consequence, ignore other stimuli for the time
while reacting with enhanced keenness to anything pro-
ceeding from the chase itself. In such case the past
operates, but does not produce any specific types of correla-
tion beyond those already mentioned. Its influence is
chiefly interesting as evidence of a certain plasticity in the
organism, which prepares the way for higher types.

(2)Acclimatisation

Such plasticity has a more definite effect in the accom-
modation to special conditions, of which probably all

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