Lamarck, the Founder of Evolution: His Life and Work

by A. S. Packard

“Ascend from the most simple to the most compound, depart from the most imperfect animalcule and ascend along the scale up to the animal richest in structure and faculties; constantly preserve the order of relation in the group, then you will hold the true thread which connects all the productions of nature; you will have a just idea of its progress, and you will be convinced that the most simple of its living productions have successively given existence to all the others.

“The series which constitutes the animal scale resides in the distribution of the groups, and not in that of the individuals and species.

“I have already said[166] that by this shaded graduation in the complication of structure I do not mean to speak of the existence of a linear and regular series of species or even genera: such a series does not exist. But I speak of a quite regularly graduated series in the principal groups, i.e., in the principal system of organizations known, which give rise to classes and to great families, series most assuredly existing both among animals and plants, although in the consideration of genera, and especially in that of species, it offers many lateral ramifications whose extremities are truly isolated points.

“However, although there has been denied, in a very modern work, the existence in the animal kingdom of a single series, natural and at the same time graduated, in the composition of the organization of beings which it comprehends, series in truth necessarily formed of groups subordinated to each other as regards structure and not of isolated species or genera, I ask where is the well-informed naturalist who would now present a different order in the arrangement of the twelve classes of the animal kingdom of which I have just given an account?

“I have already stated what I think of this view, which has seemed sublime to some moderns, and indorsed by Professor Hermann.”

Each distinct group or mass of forms has, he says, its peculiar system of essential organs, but each organ considered by itself does not follow as regular a course in its degradations (modifications).

“Indeed, the least important organs, or those least essential to life, are not always in relation to each other in their improvement or their degradation; and an organ which in one species is atrophied may be very perfect in another. These irregular variations in the perfecting and in the degradation of non-essential organs are due to the fact that these organs are oftener than the others submitted to the influences of external circumstances, and give rise to a diversity of species so considerable and so singularly ordered that instead of being able to arrange them, like the groups, in a single simple linear series under the form of a regular graduated scale, these very species often form around the groups of which they are part lateral ramifications, the extremities of which offer points truly isolated.

“There is needed, in order to change each internal system of organization, a combination of more influential circumstances, and of more prolonged duration than to alter and modify the external organs.

“I have observed, however, that, when circumstances demand, nature passes from one system to another without making a leap, provided they are allies. It is, indeed, by this faculty that she has come to form them all in succession, in proceeding from the simple to the more complex.

“It is so true that she has the power, that she passes from one system to the other, not only in two different families which are allied, but she also passes from one system to the other in the same individual.

“The systems of organization which admit as organs of respiration true lungs are nearer to systems which admit gills than those which require tracheæ. Thus not only does nature pass from gills to lungs in allied classes and families, as seen in fishes and reptiles, but in the latter she passes even during the life of the same individual, which successively possesses each system. We know that the frog in the tadpole state respires by gills, while in the more perfect state of frog it respires by lungs. We never see that nature passes from a system with tracheæ to a system with lungs.

“It is not the organs, i.e., the nature and form of the parts of the body of an animal, which give rise to the special habits and faculties, but, on the contrary, its habits, its mode of life, and the circumstances in which individuals are placed, which have, with time, brought about the form of its body, the number and condition of its organs, finally the faculties which it possesses.

. . . . . . . . .

“Time and favorable circumstances are the two principal means which nature employs to give existence to all her productions. We know that time has for her no limit, and that consequently she has it always at her disposition.

“As to the circumstances of which she has need (besoin) and which she employs every day to bring about variations in all that she continues to produce, we can say that they are in her in some degree inexhaustible.

“The principal ones arise from the influence of climate, from that of different temperatures, of the atmosphere, and from all environing surroundings (milieux); from that of the diversity of places and their situations; from that of the most ordinary habitual movements, of actions the most frequent; finally from that of the means of preservation, of the mode of life, of defence, of reproduction, etc.

“Moreover, as the result of these different influences the faculties increase and strengthen themselves by use, diversify themselves by the new habits preserved through long periods, and insensibly the conformation, the consistence—in a word, the nature and state of the parts and also of the organs—consequently participate in all these influences, are preserved and propagate themselves by generation” (Système des Animaux sans Vertèbres, p. 12).

. . . . . . . . .

“It is easy for any one to see that the habit of exercising an organ in every living being which has not reached the term of diminution of its faculties not only makes this organ more perfect, but even makes it acquire developments and dimensions which insensibly change it, with the result that with time it renders it very different from the same organ considered in another organism which has not, or has but slightly, exercised it. It is also very easy to prove that the constant lack of exercise of an organ gradually reduces it and ends by atrophying it.”

Then follow the facts regarding the mole, spalax, ant-eater, and the lack of teeth in birds, the origin of shore birds, swimming birds and perching birds, which are stated farther on.

“Thus the efforts in any direction, maintained for a long time or made habitually by certain parts of a living body, to satisfy the needs called out (exigés) by nature or by circumstances, develop these parts and cause them to acquire dimensions and a form which they never would have obtained if these efforts had not become an habitual action of the animals which have exercised them. Observations made on all the animals known would furnish examples of this.

“When the will determines an animal to any kind of action, the organs whose function it is to execute this action are then immediately provoked by the flowing there of subtile fluids, which become the determining cause of movements which perform the action in question. A multitude of observations support this fact, which now no one would doubt.

“It results from this that multiplied repetitions of these acts of organization strengthen, extend, develop, and even create the organs which are there needed. It is only necessary to closely observe that which is everywhere happening in this respect to firmly convince ourselves of this cause of developments and organic changes.

“However, each change acquired in an organ by habitual use sufficient to have formed (opéré) it is preserved by generation, if it is common to the individuals which unite in the reproduction of their kind. Finally, this change propagates itself and is then handed down (se passe) to all the individuals which succeed and which are submitted to the same circumstances, without their having been obliged to acquire it by the means which have really created it.

“Besides, in the unions between the sexes the intermixtures between individuals which have different qualities or forms are necessarily opposed to the constant propagation of these qualities and forms. We see that which in man, who is exposed to such different circumstances which influence individuals, prevents the qualities of accidental defects which they have happened to acquire from being preserved and propagated by heredity (génération).

“You can now understand how, by such means and an inexhaustible diversity of circumstances, nature, with sufficient length of time, has been able to and should produce all these results.

“If I should choose here to pass in review all the classes, orders, genera, and species of animals in existence I could make you see that the structure of individuals and their organs, faculties, etc., is solely the result of circumstances to which each species and all its races have been subjected by nature, and of habits that the individuals of this species have been obliged to contract.

“The influences of localities and of temperatures are so striking that naturalists have not hesitated to recognize the effects on the structure, the developments, and the faculties of the living bodies subject to them.

“We have long known that the animals inhabiting the torrid zone are very different from those which live in the other zones. Buffon has remarked that even in latitudes almost the same the animals of the new continent are not the same as those of the old.

“Finally the Count Lacépède, wishing to give to this well-founded fact the precision which he believed it susceptible, has traced twenty-six zoölogical divisions on the dry parts of the globe, and eighteen over the ocean; but there are many other influences than those which depend on localities and temperatures.

“Everything tends, then, to prove my assertion—namely, that it is not the form either of the body or of its parts which has given rise to habits and to the mode of life of animals, but, on the contrary, it is the habits, the mode of life, and all the other influential circumstances which have with time produced the form of the bodies and organs of animals. With new forms new faculties have been acquired, and gradually nature has arrived at the state where we actually see it.

. . . . . . . . .

“Finally as it is only at that extremity of the animal kingdom where occur the most simply organized animals that we meet those which may be regarded as the true germs of animality, and it is the same at the same end of the vegetable series; is it not at this end of the scale, both animal and vegetable, that nature has commenced and recommenced without ceasing the first germ of her living production? Who is there, in a word, who does not see that the process of perfection of those of these first germs which circumstances have favored will gradually and after the lapse of time give rise to all the degrees of perfection and of the composition of the organization, from which will result this multiplicity and this diversity of living beings of all orders with which the exterior surface of our globe is almost everywhere filled or covered?

“Indeed, if the manner (usage) of life tends to develop the organization, and even to form and multiply the organs, as the state of an animal which has just been born proves it, compared to that where it finds itself when it has reached the term where its organs (beginning to deteriorate) cease to make new developments; if, then, each particular organ undergoes remarkable changes, according as it is exercised and according to the manner of which I have shown you some examples, you will understand that in carrying you to the end of the animal chain where are found the most simple organizations, and that in considering among these organizations those whose simplicity is so great that they lie at the very door of the creative power of nature, then this same nature—that is to say, the state of things which exist—has been to form directly the first beginnings of organization; she has been able, consequently, by the manner of life and the aid of circumstances which favor its duration, to progressively render perfect its work, and to carry it to the point where we now see it.

“Time is wanting to present to you the series of results of my researches on this interesting subject, and to develop—

“1. What really is life.

“2. How nature herself creates the first traces of organization in appropriate groups where it had not existed.

“3. How the organic or vital movement is excited by it and held together with the aid of a stimulating and active cause which she has at her disposal in abundance in certain climates and in certain seasons of the year.

“4. Finally, how this organic movement, by the influence of its duration and by that of the multitude of circumstances which modify its effects, develops, arranges, and gradually complicates the organs of the living body which possesses them.

“Such has been without doubt the will of the infinite wisdom which reigns throughout nature; and such is effectively the order of things clearly indicated by the observation of all the facts which relate to them.” (End of the opening discourse.)

Appendix (p. 141).

On Species in Living Bodies.

“I have for a long time thought that species were constant in nature, and that they were constituted by the individuals which belong to each of them.

“I am now convinced that I was in error in this respect, and that in reality only individuals exist in nature.

“The origin of this error, which I have shared with many naturalists who still hold it, arises from the long duration, in relation to us, of the same state of things in each place which each organism inhabits; but this duration of the same state of things for each place has its limits, and with much time it makes changes in each point of the surface of the globe, which produces changes in every kind of circumstances for the organisms which inhabit it.

“Indeed, we may now be assured that nothing on the surface of the terrestrial globe remains in the same state. Everything, after a while, undergoes different changes, more or less prompt, according to the nature of the objects and of circumstances. Elevated areas are constantly being lowered, and the loose material carried down to the lowlands. The beds of rivers, of streams, of even the sea, are gradually removed and changed, as also the climate;[167] in a word, the whole surface of the earth gradually undergoes a change in situation, form, nature, and aspect. We see on every hand what ascertained facts prove; it is only necessary to observe and to give one’s attention to be convinced of it.

“However, if, relatively to living beings, the diversity of circumstances brings about for them a diversity of habits, a different mode of existence, and, as the result, modifications in their organs and in the shape of their parts, one should believe that very gradually every living body whatever would vary in its organization and its form.

“All the modifications that each living being will have undergone as the result of change of circumstances which have influenced its nature will doubtless be propagated by heredity (génération). But as new modifications will necessarily continue to operate, however slowly, not only will there continually be found new species, new genera, and even new orders, but each species will vary in some part of its structure and its form.

“I very well know that to our eyes there seems in this respect a stability which we believe to be constant, although it is not so truly; for a very great number of centuries may form a period insufficient for the changes of which I speak to be marked enough for us to appreciate them. Thus we say that the flamingo (Phœnicopterus) has always had as long legs and as long a neck as have those with which we are familiar; finally, it is said that all animals whose history has been transmitted for 2,000 or 3,000 years are always the same, and have lost or acquired nothing in the process of perfection of their organs and in the form of their different parts. We may be assured that this appearance of stability of things in nature will always be taken for reality by the average of mankind, because in general it judges everything only relatively to itself.

“But, I repeat, this consideration which has given rise to the admitted error owes its source to the very great slowness of the changes which have gone on. A little attention given to the facts which I am about to cite will afford the strongest proof of my assertion.

“What nature does after a great length of time we do every day by suddenly changing, as regards a living being, the circumstances in which it and all the individuals of its species are placed.

“All botanists know that the plants which they transplant from their natal spot into gardens for cultivation there gradually undergo changes which in the end render them unrecognizable. Many plants naturally very hairy, there become glabrous or nearly so; a quantity of those which were procumbent or trailing there have erect stems; others lose their spines or their thorns; finally, the dimensions of parts undergo changes which the circumstances of their new situation infallibly produce. This is so well known that botanists prefer not to describe them, at least unless they are newly cultivated. Is not wheat (Triticum sativum) a plant brought by man to the state wherein we actually see it, which otherwise I could not believe? Who can now say in what place its like lives in nature?

“To these known facts I will add others still more remarkable, and which confirm the view that change of circumstances operates to change the parts of living organisms.

“When Ranunculus aquatilis lives in deep water, all it can do while growing is to make the end of its stalks reach the surface of the water where they flourish. Then all the leaves of the plant are finely cut or pinked.[168] If the same plant grows in shallower water the growth of its stalks may give them sufficient extent for the upper leaves to develop out of the water; then its lower leaves only will be divided into hair-like joints, while the upper ones will be simple, rounded, and a little lobed.[169] This is not all: when the seeds of the same plant fall into some ditch where there is only water or moisture sufficient to make them germinate, the plant develops all its leaves in the air, and then none of them is divided into capillary points, which gives rise to Ranunculus hederaceus, which botanists regard as a species.

“Another very striking proof of the effect of a change of circumstances on a plant submitted to it is the following:

“It is observed that when a tuft of Juncus bufonius grows very near the edge of the water in a ditch or marsh this rush then pushes out filiform stems which lie in the water, are there deformed, becoming disturbed (traçantes), proliferous, and very different from that of Juncus bufonius which grows out of water. This plant, modified by the circumstances I have just indicated, has been regarded as a distinct species; it is the Juncus supinus of Rotte.[170]

“I could also give citations to prove that the changes of circumstances relative to organisms necessarily change the influences which they undergo on the part of all that which environs them or which acts on them, and so necessarily bring about changes in their size, their shape, their different organs.

“Then among living beings nature seems to me to offer in an absolute manner only individuals which succeed one another by generation.

“However, in order to facilitate the study and recognition of these organisms, I give the name of species to every collection of individuals which during a long period resemble each other so much in all their parts that these individuals only present small accidental differences which, in plants, reproduction by seeds causes to disappear.

“But, besides that at the end of a long period the totality of individuals of such a species change as the circumstances which act on them, those of these individuals which from special causes are transported into very different situations from those where the others occur, and then constantly submitted to other influences—the former, I say, assume new forms as the result of a long habit of this other mode of existence, and then they constitute a new species, which comprehends all the individuals which occur in the same condition of existence. We see, then, the faithful picture of that which happened in this respect in nature, and of that which the observation of its acts can alone discover to us.”

III. Lamarck’s Views on Species, as published in 1803.

In the opening lecture[171] of his course at the Museum of Natural History, delivered in prairial (May 20–June 18), 1803, we have a further statement of the theoretical views of Lamarck on species and their origin. He addresses his audience as “Citoyens,” France still being under the régime of the Republic.

The brochure containing this address is exceedingly rare, the only copy existing, as far as we know, being in the library of the Museum of Natural History in Paris. The author’s name is not even given, and there is no imprint. Lamarck’s name, however, is written on the outside of the cover of the copy we have translated. At the end of the otherwise blank page succeeding the last page (p. 46) is printed the words: Esquisse d’un Philosophie zoologique, the preliminary sketch, however, never having been added.

He begins by telling his hearers that they should not desire to burden their memories with the infinite details and immense nomenclature of the prodigious quantity of animals among which we distinguish an illimitable number of species, “but what is more worthy of you, and of more educational value, you should seek to know the course of nature.” “You may enter upon the study of classes, orders, genera, and even of the most interesting species, because this would be useful to you; but you should never forget that all these subdivisions, which could not, however, be well spared, are artificial, and that nature does not recognize any of them.”

“In the opening lecture of my last year’s course I tried to convince you that it is only in the organization of animals that we find the foundation of the natural relations between the different groups, where they diverge and where they approach each other. Finally, I tried to show you that the enormous series of animals which nature has produced presents, from that of its extremities where are placed the most perfect animals, down to that which comprises the most imperfect, or the most simple, an evident modification, though irregularly defined (nuancé), in the structure of the organization.

“To-day, after having recalled some of the essential considerations which form the base of this great truth; after having shown you the principal means by which nature is enabled to create (opérer) her innumerable productions and to vary them infinitely; finally, after having made you see that in the use she has made of her power of generating and multiplying living beings she has necessarily proceeded from the more simple to the more complex, gradually complicating the organization of these bodies, as also the composition of their substance, while also in that which she has done on non-living bodies she has occupied herself unremittingly in the destruction of all preëxistent combinations, I shall undertake to examine under your eyes the great question in natural history—What is a species among organized beings?

“When we consider the series of animals, beginning at the end comprising the most perfect and complicated, and passing down through all the degrees of this series to the other end, we see a very evident modification in structure and faculties. On the contrary, if we begin with the end which comprises animals the most simple in organization, the poorest in faculties and in organs—in a word, the most imperfect in all respects—we necessarily remark, as we gradually ascend in the series, a truly progressive complication in the organization of these different animals, and we see the organs and faculties of these beings successively multiplying and diversifying in a most remarkable manner.

“These facts once known present truths which are, to some extent, eternal; for nothing here is the product of our imagination or of our arbitrary principles; that which I have just explained rests neither on systems nor on any hypothesis: it is only the very simple result of the observation of nature; hence I do not fear to advance the view that all that one can imagine, from any motives whatever, to contradict these great verities will always be destroyed by the evidence of the facts with which it deals.

“To these facts it is necessary to add these very important considerations, which observation has led me to perceive, and the basis of which will always be recognized by those who pay attention to them; they are as follows:

“Firstly, the exercise of life, and consequently of organic movement, constitutes its activity, tends, without ceasing, not only to develop and to extend the organization, but it tends besides to multiply the organs and to isolate them in special centres (foyers). To make sure whether the exercise of life tends to extend and develop the organization, it suffices to consider the state of the organs of any animal which has just been born, and to compare them in this condition with what they are when the animal has attained the period when its organs cease to receive any new development. Then we will see on what this organic law is based, which I have published in my Recherches sur les Corps vivans (p. 8), i.e., that—

“‘The special property of movement of fluids in the supple parts of the living body which contain them is to open (frayer) there routes, places of deposit and tissues; to create there canals, and consequently different organs; to cause these canals and these organs to vary there by reason of the diversity both of the movements as well as the nature of the fluids which occur there; finally to enlarge, to elongate, to divide and to gradually strengthen (affermir) these canals and their organs by the matters which are formed in the fluids in motion, which incessantly separate themselves, and a part of which is assimilated and united with organs while the rest is rejected.’

“Secondly, the continual employment of an organ, especially if it is strongly exercised, strengthens this organ, develops it, increases its dimensions, enlarges and extends its faculties.

“This second law of effects of exercise of life has been understood for a long time by those observers who have paid attention to the phenomena of organization.

“Indeed, we know that all the time that an organ, or a system of organs, is rigorously exercised throughout a long time, not only its power, and the parts which form it, grow and strengthen themselves, but there are proofs that this organ, or system of organs, at that time attracts to itself the principal active forces of the life of the individual, because it becomes the cause which, under these conditions, makes the functions of other organs to be diminished in power.

“Thus not only every organ or every part of the body, whether of man or of animals, being for a long period and more vigorously exercised than the others, has acquired a power and facility of action that the same organ could not have had before, and that it has never had in individuals which have exercised less, but also we consequently remark that the excessive employment of this organ diminishes the functions of the others and proportionately enfeebles them.

“The man who habitually and vigorously exercises the organ of his intelligence develops and acquires a great facility of attention, of aptitude for thought, etc., but he has a feeble stomach and strongly limited muscular powers. He, on the contrary, who thinks little does not easily, and then only momentarily fixes his attention, while habitually giving much exercise to his muscular organs, has much vigor, possesses an excellent digestion, and is not given to the abstemiousness of the savant and man of letters.

“Moreover, when one exercises long and vigorously an organ or system of organs, the active forces of life (in my opinion, the nervous fluid) have taken such a habit of acting (porter) towards this organ that they have formed in the individual an inclination to continue to exercise which it is difficult for it to overcome.

“Hence it happens that the more we exercise an organ, the more we use it with facility, the more does it result that we perceive the need (besoin) of continuing to use it at the times when it is placed in action. So we remark that the habit of study, of application, of work, or of any other exercise of our organs or of any one of our organs, becomes with time an indispensable need to the individual, and often a passion which it does not know how to overcome.

“Thirdly, finally, the effort made by necessity to obtain new faculties is aided by the concurrence of favorable circumstances; they create (créent) with time the new organs which are adapted (propres) to their faculties, and which as the result develop after long use (qu’en suite un long emploi développe).

“How important is this consideration, and what light it spreads on the state of organization of the different animals now living!

“Assuredly it will not be those who have long been in the habit of observing nature, and who have followed attentively that which happens to living individuals (to animals and to plants), who will deny that a great change in the circumstances of their situation and of their means of existence forces them and their race to adopt new habits; it will not be those, I say, who attempt to contest the foundation of the consideration which I have just exposed.

“They can readily convince themselves of the solidity of that which I have already published in this respect.[172]

“I have felt obliged to recall to you these great considerations, a sketch of which I traced for you last year, and which I have stated for the most part in my different works, because they serve, as you have seen, as a solution of the problem which interests so many naturalists, and which concerns the determination of species among living bodies.

“Indeed, if in ascending in the series of animals from the most simply organized animalcule, as from the monad, which seems to be only an animated point, up to the animals the most perfect, or whose structure is the most complicated—in a word, up to animals with mammæ—you observe in the different orders which comprise this great series a gradation, shaded (nuancé), although irregular, in the composition of the organization and in the increasing number of faculties, is it not evident that in the case where nature would exert some active power on the existence of these organized bodies she has been able to make them exist only by beginning with the most simple, and that she has been able to form directly among the animals only that which I call the rough sketches or germs (ébauches) of animality—that is to say, only these animalcules, almost invisible and to some extent without consistence, that we see develop spontaneously and in an astonishing abundance in certain places and under certain circumstances, while only in contrary circumstances are they totally destroyed?

“Do we not therefore perceive that by the action of the laws of organization, which I have just now indicated, and by that of different means of multiplication which are due to them (qui en dérivent), nature has in favorable times, places, and climates multiplied her first germs (ébauches) of animality, given place to developments of their organizations, rendered gradually greater the duration of those which have originally descended from them, and increased and diversified their organs? Then always preserving the progress acquired by the reproductions of individuals and the succession of generations, and aided by much time and by a slow but constant diversity of circumstances, she has gradually brought about in this respect the state of things which we now observe.

“How grand is this consideration, and especially how remote is it from all that is generally thought on this subject! Moreover, the astonishment which its novelty and its singularity may excite in you requires that at first you should suspend your judgment in regard to it. But the observation which establishes it is now on record (consignée), and the facts which support it exist and are incessantly renewed; however, as they open a vast field to your studies and to your own researches, it is to you yourselves that I appeal to pronounce on this great subject when you have sufficiently examined and followed all the facts which relate to it.

“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 classes of the two organic kingdoms (the animals and the plants). It is in the classes 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 circumstances.

“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 constituent 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 algæ, 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 classes, 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 constituency, 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 principal 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 circumstances, 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 dû s’opérer) 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 embarrassed 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 constituting 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?

“Assuredly, 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 embarrassment 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 constituting a particular species.

“I repeat, the richer our collections become, the more numerous are the proofs that all is more or less shaded (nuancé), 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 classes 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 passed from shade to shade without having remarked any differences worth noticing.

“I ask what experienced zoölogist 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 multitude of known polyps of all orders of radiates, worms, and especially of insects, where the simple genera of Papilio, Phalæna, Noctua, Tinea, Musca, Ichneumon, Curculio, Capricorn, Scarabæus, 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 shells 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 lacunæ 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 participate 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 circumstances, 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 grass, 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 passed 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 circumstances 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 (défauts) 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, constitute 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 (ébauches) of organization, which have been badly characterized by the expression of “spontaneous generations” (qu’on a désignées mal-à-propos par l’expression de Générations spontanées).

“3. That the first germs (ébauches) of the animals and plants were formed in favorable places and circumstances. 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 circumstances they have been differentiated, as also the different parts (elles les ont diversifiés 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 circumstances 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 circumstances, 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 système) 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 class 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 assign 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 constitute 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.”