casionally left
uncovered for a short time, they learn to keep their shells shut,
and live for a much longer time when removed from the water. If
oysters can learn by experience, lower worms probably can do the
same.

Certain experiments made on sea-anemones, actinae animals a little
more highly organized than hydra, demand repetition under careful
observation.[A] The observer placed on one of the tentacles of a
sea-anemone a bit of paper which had been dipped in beef-juice. It
was seized and carried to the mouth and here discarded. This
tentacle after one or two experiments refused to have anything more
to do with it. But other tentacles could be successively cheated.
The nerve-cells governing each tentacle appear to have been able to
learn by experience, but each group in the diffuse nervous system
had to learn separately. The dawn of this much of intelligence far
down in the animal kingdom would not be surprising, for the
selection and grasping of food has always involved higher mental
power than most of the actions of these lowest animals. Memory goes
far down in the animal kingdom. Perhaps, as Professor Haeckel has
urged, it is an ultimate mental property of protoplasm. And the
memory of past experience would continually tend to modify habit or
instinct.

[Footnote A: These experiments have been continued with most
interesting and valuable results by Dr. G.H. Parker, of Harvard
University.]

It is unsafe, therefore, to say just where intelligence begins. At a
certain point we find dim traces of it; below that we have failed to
find them. But that they will not be found, we dare not affirm. In
the highest insects instinct predominates, but marks of intelligence
are fairly abundant. Ants and wasps modify their habits to suit
emergencies which instinct alone could hardly cope with. Bees learn
to use grafting wax instead of propolis to stop the chinks in their
hives, and soon cease to store up honey in a warm climate.

Our knowledge of vertebrate psychology is not yet sufficient to give
a history of the struggle for supremacy between instinct and
intelligence, between inherited tendency and the consciousness of
the individual. But the outcome is evident; intelligence prevails,
instinct wanes. The actions of the young may be purely instinctive;
it is better that they should be. But instinct in the adult is more
and more modified by intelligence gained by experience. There is
perhaps no more characteristic i