regained liberty of movement, and awakens in just the degree to which the vegetable has reconquered this liberty. Nevertheless, consciousness and unconsciousness mark the directions in which the two kingdoms have developed, in this sense, that to find the best specimens of consciousness in the animal we must ascend to the highest representatives of the series, whereas, to find probable cases of vegetable consciousness, we must descend as low as possible in the scale of plants — down to the zoospores of the algae, for instance, and, more generally, to those unicellular organ- isms which may be said to hesitate between the vegetable form and animality. From this standpoint, and in this measure, we should define the animal by sensibility and awakened consciousness, the vegetable by consciousness asleep and by insensibility.
To sum up, the vegetable manufactures organic sub- stances directly with mineral substances; as a rule, this aptitude enables it to dispense with movement and so with feeling. Animals, which are obliged to go in search of their food, have evolved in the direction of locomotor activity, and consequently of a consciousness more and more distinct, more and more ample.
Now, it seems to us most probable that the animal cell and the vegetable cell are derived from a common stock, and that the first living organisms oscillated be- tween the vegetable and animal form, participating in both at once. Indeed, we have just seen that the char- acteristic tendencies of the evolution of the two kingdoms, although divergent, coexist even now, both in the plant and in the animal. The proportion alone differs. Or- dinarily, one of the two tendencies covers or crushes down the other, but in exceptional circumstances the suppressed one starts up and regains the place it had lost. The
nj
The Animal
mobility and consciousness of the vegetable cell are not so sound asleep that they cannot rouse themselves when circumstances permit or demand it; and, on the other hand, the evolution of the animal kingdom has always been re- tarded, or stopped, or dragged back, by the tendency it has kept toward the vegetative life. However full, how- ever overflowing the activity of an animal species may appear, torpor and unconsciousness are always lying in wait for it. It keeps up its r61e only by effort, at the price of fatigue. Along the route on which the animal has evolved, there have been numberless shortcomings and cases of decay, generally associated with parasitic habits; they are so many shuntings on to the vegetative life. Thus, everything bears out the belief that vegetable and animal are descended from a common ancestor which united the tendencies of both in a rudimentary state.
But the two tendencies mutually implied in this rudi- mentary form became dissociated as they grew. Hence the world of plants with its fixity and insensibility, hence the animals with their mobility and consciousness. There is no need, in order to explain, this dividing into two, to bring in any mysterious force. It is enough to point out that the living being leans naturally toward what is most convenient to it, and that vegetables and animals have chosen two different kinds of convenience in the way of procuring the carbon and nitrogen they need. Vegetables continually and mechanically draw these elements from an environment that continually provides it. Animals, by action that is discontinuous, concentrated in certain moments, and conscious, go to find these bodies in organ- isms that have already fixed them. They are two different waj^ of being industrious, or perhaps we may prefer to say, of being idle. For this very reason we doubt whether nervous elements, however rudimentary, will ever be found
114 CREATIVE EVOLUTION iohap.**
in the plant. What coiresponda in it to the directing will of the animal is, we believe, the direction in which it bends the energy of the solar radiation when it uses it to break the connection of the carbon with the oxygen in carbonic acid. What corresponds in it to the sensibility of the ani- mal is the impressionability, quite of its kind, of its chioro- phyl light. Now, a nei-vous system being pre-eminently a mechanism which serves as intermediary between sen- sations and volitions, the true "nervous system" of the plant seems to be the mechanism or rather chemicism sui generis which serves as intermediary between the im- pressionability of its chlorophyl to light and the produc- ing of starch: which amounts to saying that the plant can have no nervous elements, and that the same impetus that has led the animal to give itself nerves and nerve centres must have ended, in ike plant, in the chloropkyllian function.'
This first glance over the organized world will enable
UB to ascertain more precisely what unites the two king-
doms, and also what separates them.
Suppose, as we suggested in the preceding chapter, that at the root of life there is an effort to engraft on to the necessity of physical forces the largest possible amount of indetermination. This effort cannot result in the creation of energy, or, if it does, the ciuantity created does not belong to the order of magnitude apprehended
Juit M the plant, in certain cases, recovers the faculty at moving »ctively which elumbers in it, ao the animal, in exceptional ciroum- ■tances, can repUce itself in the conditions of the vegetative lite and develop in il«elf an equivalent of the cblorophyllian function. II appears, indeed, from recent experimente of Maria von Linden, th&t the chrysalides and the caterpillars of certain lepidoptera, under the influence of light, fix the carbon of the carbonic acid contained in the atmosphere (M. von Linden, " L 'Assimilation de I'acide carbonique paries chiyBalideadeUpidopl£re8,"C.A.de taSoc. de b%otogit,lMS, pp. 693 ffO-
no
by our senses and instruments of measurement, our ex- perience and science. All that the effort can do, then, is to make the best of a pre-existing energy which it finds at its disposal. Now, it finds only one way of succeed- ing in this, namely, to secure such an accumulation of potential energy from matter, that it can get, at any moment, the amount of work it needs for its action, simply by pulling a trigger. The effort itself possesses only that power of releasing. But the work of releasing, although always the same and always smaller than any given quantity, will be the more effective the heavier the weight it makes fall and the greater the height — or, in other words, the greater the sum of potential energy accumulated and disposable. As a matter of fact, the principal source of energy usable on the surface of our planet is the sun. So the problem was this: to obtain from the sun that it should partially and provisionally suspend, here and there, on the surface of the earth, its continual outpour of usable energy, and store a certain quantity of it, in the form of unused energy, in appropriate reservoirs, whence it could be drawn at the desired moment, at the desired spot, in the desired direction. The sub- stances forming the food of animals are just such reservoirs. Made of very complex molecules holding a considerable amount of chemical energy in the potential state, they are like explosives which only need a spark to set free the energy stored within them. Now, it is probable that life tended at the beginning to compass at one and the same time both the manufacture of the explosive and the explosion by which it is utilized. In this case, the same organism that bad directly stored the energy of the solar radiation would have expended it in free movements in space. And for that reason we must presume that the first hving b^ngs sought on the one hand to accumulate, without
oeaang, energy borrowed from the eun, and on the other hand to expend it, in a discontinuous and explosive way, in movements of locomotion. Even to-day, perhaps, a chlorophyl-bearing Infusorian such as the Euglena may Bymbolize this primordial tendency of life, though in a mean form, incapable of evolving. Is the divergent development of the two kingdoms related to what one may call the oblivion of each kingdom as regards one of the two halves of the programme? Or rather, which is more Ukely, was the very nature of the matter, that life found confronting it on our planet, opposed to the possibihty of the two tendencies evolving very far together in the same organism? What is certain is that the vegetable has trended principally in the first direction and the animal in the second. But if, from the very first, in making the explosive, nature had for object the explosion, then it is the evolution of the animal, rather than that of the vege- table, that indicates, on the whole, the fundamental di- rection of life.
The "harmony" of the two kingdoms, the comple- mentary characters they display, might then be due to the fact that they develop two tendencies which at first were fused in one. The more the single original tendency grows, the harder it finds it to keep united in the same hving being those two elements which in the rudimentary state implied each other. Hence a parting in two, hence two divergent evolutions; hence also two scries of char- acters oppased in certain points, complementary in others, but, whether opposed or complementary, always preserving an appearance of kinship. While the animal evolved, not without accidents along the way, toward a freer and freer expenditure of discontinuous energy, the plant per- fected rather its system of accumulation ^^ithout mo\'ing. W« shall not dwell on this second point. Suffice it to
say that the plant must have been greatly beneBted, in its turn, by a new di\'ision, analogous to that between plants and animals. White the primitive vegetable cell had to fix by itself both its carbon and its nitrogen, it became able almost to give up the second of these two functions as soon as microscopic vegetables came forward which leaned in this direction exclusively, and even special- ized diversely in this still complicated business. The microbes that fix the nitrogen of the air and those which convert the ammoniacal compounds into nitrous ones, and these again into nitrates, have, by the same splitting up of a tendency primitively one, rendered to the whole vegetable world the same kind of service as the vegetables in general have rendered to animals. If a special kingdom were to be made for these microscopic vegetables, it might be said that in the microbes of the soil, the vegetables and the animals, we have before us the analysis, carried out by the matter that life found at its disposal on our planet, of all that life contained, at the outset, in a state of reciprocal imphcation. Is this, properly speaking, a "division of labor"? These words do not give the exact idea of evolution, such as we conceive it. Wherever there is division of labor, there is assodalion and also convergence of effort. Now, the evolution we are speaking of is never achieved by means of association, but by dissociation; it never tends toward convergence, but toward divergence of efforts. The harmony between terms that are mutually complementary in certain points is not, in our opinion, produced, in course of progress, by a reciprocal adapta- tion; on the contrary, it is complete only at the start. It arises from an original identity, from the fact that the evolutionary process, splaying out like a sheaf, sunders, in proportion to their simultaneous growth, terms which at first completed each other so well that they coalesced.
(OH&P.
Now, the elements into which a tendency splits ap are far from possessing the same importance, or, above all, the same power to evolve. We have just distinguished three different kingdoms, if one may so express it, in the organized world. While the first comprises only micro- organisms which have remained in the rudimentary state, animals and vegetables have taken their flight toward very lofty fortunes. Such, indeed, is generally the case when a tendency divides. Among the divergent develop- ments to which it gives rise, some go on indefinitely, others come more or less quickly to the end of their tether. These latter do not issue directly from the primitive tendency, but from one of the elements into which it has divided; they are residual developments made and left behind on the way by some truly elementary tendency which continues to evolve. Now, these truly elementary ten- dencies, we think, bear a mark by which they may be recognized.