ed by a
membrane of cellulose, which condemns it to immobility. And, from the
bottom to the top of the vegetable kingdom, there are the same habits
growing more and more sedentary, the plant having no need to move, and
finding around it, in the air and water and soil in which it is placed,
the mineral elements it can appropriate directly. It is true that
phenomena of movement are seen in plants. Darwin has written a
well-known work on the movements of climbing plants. He studied also the
contrivances of certain insectivorous plants, such as the Drosera and
the Dionaea, to seize their prey. The leaf-movements of the acacia, the
sensitive plant, etc., are well known. Moreover, the circulation of the
vegetable protoplasm within its sheath bears witness to its relationship
to the protoplasm of animals, whilst in a large number of animal species
(generally parasites) phenomena of fixation, analogous to those of
vegetables, can be observed.[53] Here, again, it would be a mistake to
claim that fixity and mobility are the two characters which enable us to
decide, by simple inspection alone, whether we have before us a plant or
an animal. But fixity, in the animal, generally seems like a torpor into
which the species has fallen, a refusal to evolve further in a certain
direction; it is closely akin to parasitism and is accompanied by
features that recall those of vegetable life. On the other hand, the
movements of vegetables have neither the frequency nor the variety of
those of animals. Generally, they involve only part of the organism and
scarcely ever extend to the whole. In the exceptional cases in which a
vague spontaneity appears in vegetables, it is as if we beheld the
accidental awakening of an activity normally asleep. In short, although
both mobility and fixity exist in the vegetable as in the animal world,
the balance is clearly in favor of fixity in the one case and of
mobility in the other. These two opposite tendencies are so plainly
directive of the two evolutions that the two kingdoms might almost be
defined by them. But fixity and mobility, again, are only superficial
signs of tendencies that are still deeper.

Between mobility and consciousness there is an obvious relationship. No
doubt, the consciousness of the higher organisms seems bound up with
certain cerebral arrangements. The more the nervous system develops,
the more numerous and more precise become the movements among which it
can choose; the clearer,