lopment acts as a signal to the next.

In the same way the characteristic element in what is done by memory, or
by that "unconscious memory" {51b} known as habit, is the association of
a chain of thoughts or actions each calling forth the next.

What I wish to insist on is, that the process I have called
action-by-signal is of the same type as action-by-association, and
therefore allied to habit and memory. The plants alive to-day are the
successful ones who have inherited from successful ancestors the power of
curving in certain ways, when, by accidental deviations from their normal
attitude, some change of pressure is produced in their protoplasm. With
the pianist the playing of A has become tied to, entangled or associated
with, the playing of B, so that the striking of note A has grown to be a
signal to the muscles to strike B. Similarly in the plant, the act of
bending has become tied to, entangled or associated with, that change in
the protoplasm due to the altered position. There is no mechanical
necessity that B should follow A in the tune; the sequence is owing to
the path built by habit in the man's brain. And this is equally true of
the plant, in which an hereditary habit has been built up in a brain-like
root-tip.

The capacities of plants of which I have spoken have been compared to
instincts, and if I prefer to call them reflexes it is because instinct
is generally applied to actions with something of an undoubted mental
basis. I do not necessarily wish it to be inferred that there can be
nothing in plants which may possibly be construed as the germ of
consciousness--nothing psychic, to use a convenient term; but it is
clearly our duty to explain the facts, if possible, without assuming a
psychological resemblance between plants and human beings, lest we go
astray into anthropomorphism or sentimentality, and sin against the law
of parsimony, which forbids us to assume the action of higher causes when
lower will suffice.

The problem is clearly one for treatment by evolutionary method--for
instance, by applying the principle of continuity. {53a} Man is
developed from an ovum, and since man has consciousness it is allowable
to suppose that the speck of protoplasm from which he develops has a
quality which can grow into consciousness, and, by analogy, that other
protoplasmic bodies, for instance those found in plants, have at least
the ghosts of similar qualities. But the principle of continuity ma