Lamarck, the Founder of Evolution Part 24

"If among living bodies there are any the consideration of whose organization and of the phenomena which they produce can enlighten us as to the power of nature and its course relatively to the existence of these bodies, also as to the variations which they undergo, we certainly have to seek for them in the lowest cla.s.ses of the two organic kingdoms (the animals and the plants). It is in the cla.s.ses which comprise the living bodies whose organization is the least complex that we can observe and bring together facts the most luminous, observations the most decisive on the origin of these bodies, on their reproduction and their admirable diversification, finally on the formation and the development of their different organs, the whole process being aided by the concurrence of generations, of time, and of circ.u.mstances.

"It is, indeed, among living bodies the most multiplied, the most numerous in nature, the most prompt and easy to regenerate themselves, that we should seek the most instructive facts bearing on the course of nature and on the means she has employed to create her innumerable productions. In this case we perceive that, relatively to the animal kingdom, we should chiefly give our attention to the invertebrate animals, because their enormous multiplicity in nature, the singular diversity of their systems of organization and of their means of multiplication, their increasing simplification, and the extreme fugacity of those which compose the lowest orders of these animals, show us much better than the others the true course of nature, and the means which she has used and which she is still incessantly employing to give existence to all the living bodies of which we have knowledge.

"Her course and her means are without doubt the same for the production of the different plants which exist. And, indeed, though it is not believed, as some naturalists have wrongly held, but without proof, that plants are bodies more simple in organization than the most simple animals, it is a veritable error which observation plainly denies.

"Truly, vegetable substance is less surcharged with const.i.tuent principles than any animal substance whatever, or at least most of them, but the substance of a living body and the organization of these bodies are two very different things. But there is in plants, as in animals, a true gradation in organization from the plant simplest in organization and parts up to plants the most complex in structure and with the most diversified organs.

"If there is some approach, or at least some comparison to make between vegetables and animals, this can only be by opposing plants the most simply organized, like fungi and algae, to the most imperfect animals like the polyps, and especially the amorphous polyps, which occur in the lowest order.

"At present we clearly see that in order to bring about the existence of animals of all the cla.s.ses, of all the orders, and of all the genera, nature has had to begin by giving existence to those which are the most simple in organization and lacking most in organs and faculties, the frailest in const.i.tuency, the most ephemeral, the quickest and easiest to multiply; and we shall find in the _amorphous_ or _microscopic polyps_ the most striking examples of this simplification of organization, and the indication that it is solely among them that occur the astonishing germs of animality.

"At present we only know the princ.i.p.al law of the organization, the power of the exercise of the functions of life, the influence of the movement of fluids in the supple parts of organic bodies, and the power which the regenerations have of conserving the progress acquired in the composition of organs.

"At present, finally, relying on numerous observations, seeing that with the aid of much time, of changes in local circ.u.mstances, in climates, and consequently in the habits of animals, the progression in the complication of their organization and in the diversity of their parts has gradually operated (_a du s'operer_) in a way that all the animals now known have been successively formed such as we now see them, it becomes possible to find the solution of the following question:

"What is a _species_ among living beings?

"All those who have much to do with the study of natural history know that naturalists at the present day are extremely embarra.s.sed in defining what they mean by the word species.

"In truth, observation for a long time has shown us, and shows us still in a great number of cases, collections of individuals which resemble each other so much in their organization and by the _ensemble_ of their parts that we do not hesitate to regard these collections of similar individuals as const.i.tuting so many species.

"From this consideration we call _species_ every collection of individuals which are alike or almost so, and we remark that the regeneration of these individuals conserves the species and propagates it in continuing successively to reproduce similar individuals.

"Formerly it was supposed that each species was immutable, as old as nature, and that she had caused its special creation by the Supreme Author of all which exists.

"But we can impose on him laws in the execution of his will, and determine the mode which he has been pleased to follow in this respect, so it is only in this way that he permits us to recognize it by the aid of observation. Has not his infinite power created an order of things which successively gives existence to all that we see as well as to all that which exists and which we do not know?

"a.s.suredly, whatever has been his will, the omnipotence of his power is always the same; and in whatever way this supreme will has been manifested, nothing can diminish its greatness. As regards, then, the decrees of this infinite wisdom, I confine myself to the limits of a simple observer of nature. Then, if I discover anything in the course that nature follows in her creations, I shall say, without fear of deceiving myself, that it has pleased its author that she possesses this power.

"The idea that was held as to species among living bodies was quite simple, easy to grasp, and seemed confirmed by the constancy in the similar form of the individuals which reproduction or generation perpetuated. There still occur among us a very great number of these pretended species which we see every day.

"However, the farther we advance in the knowledge of the different organized bodies with which almost every part of the surface of the globe is covered, the more does our embarra.s.sment increase in determining what should be regarded as species, and the greater is the reason for limiting and distinguishing the genera.

"As we gradually gather the productions of nature, as our collections gradually grow richer, we see almost all the gaps filled up, and our lines of demarcation effaced. We find ourselves compelled to make an arbitrary determination, which sometimes leads us to seize upon the slightest differences between varieties to form of them the character of that which we call species, and sometimes one person designates as a variety of such a species individuals a little different, which others regard as const.i.tuting a particular species.

"I repeat, the richer our collections become, the more numerous are the proofs that all is more or less shaded (_nuance_), that the remarkable differences become obliterated, and that the more often nature leaves it at our disposal to establish distinctions only minute, and in some degree trivial peculiarities.

"But some genera among animals and plants are of such an extent, from the number of species they contain, that the study and the determination of these species are now almost impossible. The species of these genera, arranged in series and placed together according to their natural relations, present, with those allied to them, differences so slight that they shade into each other; and because these species are in some degree confounded with one another they leave almost no means of determining, by expression in words, the small differences which distinguish them.

"There are also those who have been for a long time, and strongly, occupied with the determination of the species, and who have consulted rich collections, who can understand up to what point species, among living bodies, merge one into another (_fondent les unes dans les autres_), and who have been able to convince themselves, in the regions (_parties_) where we see isolated species, that this is only because there are wanting other species which are more nearly related, and which we have not yet collected.

"I do not mean to say by this that the existing animals form a very simple series, one everywhere equally graduated; but I say that they form a branching series, irregularly graduated, and which has no discontinuity in its parts, or which at best has not always had, if it is true that it is to be found anywhere (_s'il est vrai qu'il s'en trouve quelque part_). It results from this that the species which terminates each branch of the general series holds a place at least on one side apart from the other allied species which intergrade with them. Behold this state of things, so well known, which I am now compelled to demonstrate.

"I have no need (_besoin_) of any hypothesis or any supposition for this: I call to witness all observing naturalists.

"Not only many genera, but entire orders, and some cla.s.ses even, already present us with portions almost complete of the state of things which I have just indicated.

"However, when in this case we have arranged the species in series, and they are all well placed according to their natural relations, if you select one of them, and it results in making a leap (_saut pardessus_) over to several others, you take another one of them a little less remote; these two species, placed in comparison, will then present the greatest differences from each other. It is thus that we had begun to regard most of the productions of nature which occur at our door. Then the generic and specific distinctions were very easy to establish. But now that our collections are very much richer, if you follow the series that I have cited above, from the species that you first chose up to that which you took in the second place, and which is very different from the first, you have pa.s.sed from shade to shade without having remarked any differences worth noticing.

"I ask what experienced zoologist or botanist is there who has not thoroughly realized that which I have just explained to you?

"Or how can one study, or how can one be able to determine in a thorough way the species, among the mult.i.tude of known polyps of all orders of radiates, worms, and especially of insects, where the simple genera of Papilio, Phalaena, Noctua, Tinea, Musca, Ichneumon, Curculio, Capricorn, Scarabaeus, Cetonia, etc., etc., already contain so many closely allied species which shade into each other, are almost confounded one with another? What a host of molluscan sh.e.l.ls exist in every country and in all seas which elude our means of distinction, and exhaust our resources in this respect! Ascend to the fishes, to the reptiles, to the birds, even to the mammals, and you will see, except the lacunae which are still to be filled, everywhere shadings which take place between allied species, even the genera, and where after the most industrious study we fail to establish good distinctions. Does not botany, which considers the other series, comprising the plants, offer us, in its different parts, a state of things perfectly similar? In short, what difficulties do not arise in the study and in the determination of species in the genera Lichena, Fucus, Carex, Poa, Piper, Euphorbia, Erica, Hieracium, Solanum, Geranium, Mimosa, etc., etc.?

"When these genera were established but a small number of species were known, and then it was easy to distinguish them; but at present almost all the gaps between them are filled, and our specific differences are necessarily minute and very often insufficient.

"From this state of things well established we see what are the causes which have given rise to them; we see whether nature possesses the means for this, and if observation has been able to give us our explanation of it.

"A great many facts teach us that gradually as the individuals of one of our species change their situation, climate, mode of life, or habits, they thus receive influences which gradually change the consistence and the proportions of their parts, their form, their faculties, even their organization; so that all of them partic.i.p.ate eventually in the changes which they have undergone.

"In the same climate, very different situations and exposures at first cause simple variations in the individuals which are found exposed there; but, as time goes on, the continual differences of situation of individuals of which I have spoken, which live and successively reproduce in the same circ.u.mstances, give rise among them to differences which are, in some degree, essential to their being, in such a way that at the end of many successive generations these individuals, which originally belonged to another species, are at the end transformed into a new species, distinct from the other.

"For example, if the seeds of a gra.s.s, or of every other plant natural to a humid field, should be transplanted, by an accident, at first to the slope of a neighboring hill, where the soil, although more elevated, would yet be quite cool (_frais_) so as to allow the plant to live, and then after having lived there, and pa.s.sed through many generations there, it should gradually reach the poor and almost arid soil of a mountain side--if the plant should thrive and live there and perpetuate itself during a series of generations, it would then be so changed that the botanists who should find it there would describe it as a separate species.

"The same thing happens to animals which circ.u.mstances have forced to change their climate, manner of living, and habits; but for these the influences of the causes which I have just cited need still more time than in the case of plants to produce the notable changes in the individuals, though in the long run, however, they always succeed in bringing them about.

"The idea of defining under the word _species_ a collection of similar individuals which perpetuate the same by generation, and which have existed thus as anciently as nature, implies the necessity that the individuals of one and the same species cannot mix, in their acts of generation, with the individuals of a different species. Unfortunately observation has proved, and still proves every day, that this consideration has no basis; for the hybrids, very common among plants, and the unions which are often observed between the individuals of very different species among animals, have made us perceive that the limits between these species, supposed to be constant, are not so rigid as is supposed.

"In truth, nothing often results from these singular unions, especially when they are very incongruous, as the individuals which result from them are usually sterile; but also, when the disparities are less great, it is known that the drawbacks (_defauts_) with which it has to do no longer exist. However, this means alone suffices to gradually create the varieties which have afterwards arisen from races, and which, with time, const.i.tute that which we call _species_.

"To judge whether the idea which is formed of species has any real foundation, let us return to the considerations which I have already stated; they are, namely--

"1. That all the organic bodies of our globe are veritable productions of nature, which she has created in succession at the end of much time.

"2. That in her course nature has begun, and begins anew every day, by forming the simplest organic bodies, and that she directly forms only these--that is to say, only these first primitive germs (_ebauches_) of organization, which have been badly characterized by the expression of "spontaneous generations" (_qu'on a designees mal-a-propos par l'expression de Generations spontanees_).

"3. That the first germs (_ebauches_) of the animals and plants were formed in favorable places and circ.u.mstances. The functions of life beginning and an organic movement established, these have necessarily gradually developed the organs, so that after a time and under suitable circ.u.mstances they have been differentiated, as also the different parts (_elles les ont diversifies ainsi qui les parties_).

"4. That the power of increase in each portion of organic bodies being inherited at the first production (_effets_) of life, it has given rise to different modes of multiplication and of regeneration of individuals; and in that way the progress acquired in the composition of the organization and in the forms and the diversity of the parts has been preserved.

"5. That with the aid of sufficient time, of circ.u.mstances which have been necessarily favorable, of changes that all parts of the surface of the globe have successively undergone in their condition--in a word, with the power that new situations and new habits have in modifying the organs of bodies endowed with life--all those which now exist have been imperceptibly formed such as we see them.

"6. Finally, that according to a similar order of things, living beings, having undergone each of the more or less great changes in the condition of their organization and of their parts, that which is designated as a species among them has been insensibly and successively so formed, can have only a relative constancy in its condition, and cannot be as ancient as nature.

"But, it will be said, when it is necessary to suppose that, with the aid of much time and of an infinite variation in circ.u.mstances, nature has gradually formed the different animals that we know, would we not be stopped in this supposition by the sole consideration of the admirable diversity which we observe in the instinct of different animals, and by that of the marvels of all sorts which their different kinds of industry present?

"Will one dare to carry the spirit of system (_porter l'esprit de systeme_) to the point of saying that it is nature, and she alone, which creates this astonishing diversity of means, of ruses, of skill, of precautions, of patience, of which the industry of animals offers us so many examples! What we observe in this respect in the cla.s.s of insects alone, is it not a thousand times more than is necessary to compel us to perceive that the limits of the power of nature by no means permit her herself to produce so many marvels, and to force the most obstinate philosophy to recognize that here the will of the supreme author of all things has been necessary, and has alone sufficed to cause the existence of so many admirable things?

"Without doubt one would be rash, or rather wholly unreasonable, to pretend to a.s.sign limits to the power of the first author of all things; and by that alone no one can dare to say that this infinite power has not been able to will that which nature herself shows us she has willed.

"This being so, if I discover that nature herself brings about or causes all the wonders just cited; that she creates the organization, the life, even feeling; that she multiplies and diversifies, within limits which are not known to us, the organs and faculties of organic bodies the existence of which she sustains or propagates; that she has created in animals by the single way of _need_, which establishes and directs the habits, the source of all actions, from the most simple up to those which const.i.tute _instinct_, industry, finally reason, should I not recognize in this power of nature--that is to say, of existing things--the execution of the will of its sublime author, who has been able to will that it should have this power? Shall I any the less wonder at the omnipotence of the power of the first cause of all things, if it has pleased itself that things should be thus, than if by so many (separate) acts of his omnipotent will he should be occupied and occupy himself still continually with details of all the special creations, all the variations, and all the developments and perfections, all the destructions and all the renewals--in a word, with all the changes which are in general produced in things which exist?

"But I intend to prove in my 'Biologie' that nature possesses in her _faculties_ all that is necessary to have to be able herself to produce that which we admire in her works; and regarding this subject I shall then enter into sufficient details which I am here obliged to omit.[173]

"However, it is still objected that all we see stated regarding the state of living bodies are unalterable conditions in the preservation of their form, and it is thought that all the animals whom history has transmitted to us for two or three thousand years have always remained the same, and have lost nothing nor acquired anything in the perfecting of their organs and in the form of their parts.

"While this apparent stability has for a long time been accepted as true, it has just been attempted to establish special proofs in a report on the collections of natural history brought from Egypt by the citizen Geoffroy."

Quotes three paragraphs in which the reporters (Cuvier and Geoffroy St. Hilaire) say that the mummied animals of Thebes and Memphis are perfectly similar to those of to-day. Then he goes on to say: