Lamarck, the Founder of Evolution Part 21

The only place where we have seen any statement of Lamarck's earlier opinions is in his _Recherches sur les Causes des princ.i.p.aux Faits physiques_, which was written, as the "advertis.e.m.e.nt" states, "about eighteen years" before its publication in 1794. The treatise was actually presented April 22, 1780, to the Academie des Sciences.[161] It will be seen by the following pa.s.sages, which we translate, that, as Huxley states, this view presents a striking contrast to those to be found in the _Philosophie zoologique_:

"685. Although my sole object in this article [article premier, p. 188] has only been to treat of the physical cause of the maintenance of life of organic beings, still I have ventured to urge at the outset that the existence of these astonis.h.i.+ng beings by no means depends on nature; that all which is meant by the word nature cannot give life--namely, that all the faculties of matter, added to all possible circ.u.mstances, and even to the activity pervading the universe, cannot produce a being endowed with the power of organic movement, capable of reproducing its like, and subject to death.

"686. All the individuals of this nature which exist are derived from similar individuals, which, all taken together, const.i.tute the entire species. However, I believe that it is as impossible for man to know the physical origin of the first individual of each species as to a.s.sign also physically the cause of the existence of matter or of the whole universe. This is at least what the result of my knowledge and reflection leads me to think. If there exist any varieties produced by the action of circ.u.mstances, these varieties do not change the nature of the species (_ces varietes ne denaturent point les especes_); but doubtless we are often deceived in indicating as a species what is only a variety; and I perceive that this error may be of consequence in reasoning on this subject"

(tome ii., pp. 213-214).

It must apparently remain a matter of uncertainty whether this opinion, so decisively stated, was that of Lamarck at thirty-two years of age, and which he allowed to remain, as then stated, for eighteen years, or whether he inserted it when reading the proofs in 1794. It would seem as if it were the expression of his views when a botanist and a young man.

In his _Memoires de Physique et d'Histoire naturelle_, which was published in 1797, there is nothing said bearing on the stability of species, and though his work is largely a repet.i.tion of the _Recherches_, the author omits the pa.s.sages quoted above. Was this period of six years, between 1794 and 1800, given to a reconsideration of the subject resulting in favor of the doctrine of descent?

Huxley quotes these pa.s.sages, and then in a footnote (p. 211), after stating that Lamarck's _Recherches_ was not published before 1794, and stating that at that time it presumably expressed Lamarck's mature views, adds: "It would be interesting to know what brought about the change of opinion manifested in the _Recherches sur l'Organisation des Corps vivans_, published only seven years later."

In the appendix to this book (1802) he thus refers to his change of views: "I have for a long time thought that _species_ were constant in nature, and that they were const.i.tuted 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" (p. 141).

Some clew in answer to the question as to when Lamarck changed his views is afforded by an almost casual statement by Lamarck in the addition ent.i.tled _Sur les Fossiles_ to his _Systeme des Animaux sans Vertebres_ (1801), where, after speaking of fossils as extremely valuable monuments for the study of the revolutions the earth has pa.s.sed through at different regions on its surface, and of the changes living beings have there themselves successively undergone, he adds in parenthesis: "_Dans mes lecons j'ai toujours insiste sur ces considerations._" Are we to infer from this that these evolutionary views were expressed in his first course, or in one of the earlier courses of zoological lectures--_i.e._, soon after his appointment in 1793--and if not then, at least one or two, or perhaps several, years before the year 1800? For even if the change in his views were comparatively sudden, he must have meditated upon the subject for months and even, perhaps, years, before finally committing himself to these views in print. So strong and bold a thinker as Lamarck had already shown himself in these fields of thought, and one so inflexible and unyielding in holding to an opinion once formed as he, must have arrived at such views only after long reflection. There is also every reason to suppose that Lamarck's theory of descent was conceived by himself alone, from the evidence which lay before him in the plants and animals he had so well studied for the preceding thirty years, and that his inspiration came directly from nature and not from Buffon, and least of all from the writings of Erasmus Darwin.

FOOTNOTES:

[158] See the comparative summary of the views of the founders of evolution at the end of Chapter XVII.

[159] While Rousseau was living at Montmorency "his thought wandered confusedly round the notion of a treatise to be called 'Sensitive Morality or the Materialism of the Age,' the object of which was to examine the influence of external agencies, such as light, darkness, sound, seasons, food, noise, silence, motion, rest, on our corporeal machine, and thus, indirectly, upon the soul also."--_Rousseau_, by John Morley (p. 164).

[160] Butler's _Evolution, Old and New_ (p. 244), and Isidore Geoffroy St. Hilaire's _Histoire naturelle generale_, tome ii., p. 404 (1859).

[161] After looking in vain through both volumes of the _Recherches_ for some expression of Lamarck's earlier views, I found a mention of it in Osborn's _From the Greeks to Darwin_, p. 152, and reference to Huxley's _Evolution in Biology_, 1878 ("Darwiniana," p. 210), where the paragraphs translated above are quoted in the original.

CHAPTER XVI

THE STEPS IN THE DEVELOPMENT OF LAMARCK'S VIEWS ON EVOLUTION BEFORE THE PUBLICATION OF HIS _PHILOSOPHIE ZOOLOGIQUE_

I. _From the Systeme des Animaux sans Vertebres_ (1801).

The first occasion on which, so far as his published writings show, Lamarck expressed his evolutional views was in the opening lecture[162]

of his course on the invertebrate animals delivered in the spring of 1800, and published in 1801 as a preface to his _Systeme des Animaux sans Vertebres_, this being the first sketch or prodromus of his later great work on the invertebrate animals. In the preface of this book, referring to the opening lecture, he says: "I have glanced at some important and philosophic views that the nature and limits of this work do not permit me to develop, but which I propose to take up elsewhere with the details necessary to show on what facts they are based, and with certain explanations which would prevent any one from misunderstanding them." It may be inferred from this that he had for some time previous meditated on this theme. It will now be interesting to see what factors of evolution Lamarck employed in this first sketch of his theory.

After stating the distinctions existing between the vertebrate and invertebrate animals, and referring to the great diversity of animal forms, he goes on to say that Nature began with the most simply organized, and having formed them, "then with the aid of much time and of favorable circ.u.mstances she formed all the others."

"It appears, as I have already said, that _time_ and _favorable conditions_ are the two princ.i.p.al means which nature has employed in giving existence to all her productions. We know that for her time has no limit, and that consequently she has it always at her disposal.

"As to the circ.u.mstances of which she has had need and of which she makes use every day in order to cause her productions to vary, we can say that they are in a manner inexhaustible.

"The essential ones arise from the influence and from all the environing media (_milieux_), from the diversity of local causes (_diversite des lieux_), of habits, of movements, of action, finally of means of living, of preserving their lives, of defending themselves, of multiplying themselves, etc. Moreover, as the result of these different influences the faculties, developed and strengthened by use (_usage_), became diversified by the new habits maintained for long ages, and by slow degrees the structure, the consistence, in a word the nature, the condition of the parts and of the organs consequently partic.i.p.ating in all these influences, became preserved and were propagated by generation.[163]

"The bird which necessity (_besoin_) drives to the water to find there the prey needed for its subsistence separates the toes of its feet when it wishes to strike the water[164] and move on its surface. The skin, which unites these toes at their base, contracts in this way the habit of extending itself. Thus in time the broad membranes which connect the toes of ducks, geese, etc., are formed in the way indicated.

"But one accustomed to live perched on trees has necessarily the end of the toes lengthened and shaped in another way. Its claws are elongated, sharpened, and are curved and bent so as to seize the branches on which it so often rests.

"Likewise we perceive that the sh.o.r.e bird, which does not care to swim, but which, however, is obliged (a _besoin_) to approach the water to obtain its prey, will be continually in danger of sinking in the mud, but wis.h.i.+ng to act so that its body shall not fall into the liquid, it will contract the habit of extending and lengthening its feet. Hence it will result in the generations of these birds which continue to live in this manner, that the individuals will find themselves raised as if on stilts, on long naked feet; namely, denuded of feathers up to and often above the thighs.

"I could here pa.s.s in review all the cla.s.ses, all the orders, all the genera and species of animals which exist, and make it apparent that the conformation of individuals and of their parts, their organs, their faculties, etc., is entirely the result of circ.u.mstances to which the race of each species has been subjected by nature.

"I could prove that it is not the form either of the body or of its parts which gives rise to habits, to the mode of life of animals, but, on the contrary, it is the habits, the mode of life, and all the influential circ.u.mstances which have, with time, made up the form of the body and of the parts of animals. With the new forms new faculties have been acquired, and gradually nature has reached the state in which we actually see her" (pp. 12-15).

He then points out the gradation which exists from the most simple animal up to the most composite, since from the monad, which, so to speak, is only an animated point, up to the mammals, and from them up to man, there is evidently a shaded gradation in the structure of all the animals. So also among the plants there is a graduated series from the simplest, such as _Mucor viridescens_, up to the most complicated plant.

But he hastens to say that by this regular gradation in the complication of the organization he does not mean to infer the existence of a linear series, with regular intervals between the species and genera:

"Such a series does not exist; but I speak of a series almost regularly graduated in the princ.i.p.al groups (_ma.s.ses_) such as the great families; series most a.s.suredly existing, both among animals and among plants, but which, as regards genera and especially species, form in many places lateral ramifications, whose extremities offer truly isolated points."

This is the first time in the history of biological science that we have stated in so scientific, broad, and modern form the essential principles of evolution. Lamarck insists that time without limit and favorable conditions are the two princ.i.p.al means or factors in the production of plants and animals. Under the head of favorable conditions he enumerates variations in climate, temperature, the action of the environment, the diversity of local causes, change of habits, movement, action, variation in means of living, of preservation of life, of means of defence, and varying modes of reproduction. As the result of the action of these different factors, the faculties of animals, developed and strengthened by use, become diversified by the new habits, so that by slow degrees the new structures and organs thus arising become preserved and transmitted by heredity.

In this address it should be noticed that nothing is said of willing and of internal feeling, which have been so much misunderstood and ridiculed, or of the direct or indirect action of the environment. He does speak of the bird as wis.h.i.+ng to strike the water, but this, liberally interpreted, is as much a physiological impulse as a mental desire. No reference also is made to geographical isolation, a factor which he afterwards briefly mentioned.

Although Lamarck does not mention the principle of selection, he refers in the following way to compet.i.tion, or at least to the checks on the too rapid multiplication of the lower invertebrates:

"So were it not for the immense consumption as food which is made in nature of animals which compose the lower orders of the animal kingdom, these animals would soon overpower and perhaps destroy, by their enormous numbers, the more highly organized and perfect animals which compose the first cla.s.ses and the first orders of this kingdom, so great is the difference in the means and facility of multiplying between the two.

"But nature has antic.i.p.ated the dangerous effects of this vast power of reproduction and multiplication. She has prevented it on the one hand by considerably limiting the duration of life of these beings so simply organized which compose the lower cla.s.ses, and especially the lowest orders of the animal kingdom. On the other hand, both by making these animals the prey of each other, thus incessantly reducing their numbers, and also by determining through the diversity of climates the localities where they could exist, and by the variety of seasons--_i.e._, by the influences of different atmospheric conditions--the time during which they could maintain their existence.

"By means of these wise precautions of nature everything is well balanced and in order. Individuals multiply, propagate, and die in different ways. No species predominates up to the point of effecting the extinction of another, except, perhaps, in the highest cla.s.ses, where the multiplication of the individuals is slow and difficult; and as the result of this state of things we conceive that in general species are preserved" (p. 22).

Here we have in antic.i.p.ation the doctrine of Malthus, which, as will be remembered, so much impressed Charles Darwin, and led him in part to work out his principle of natural selection.

The author then taking up other subjects, first a.s.serts that among the changes that animals and plants unceasingly bring about by their production and _debris_, it is not the largest and most perfect animals which have caused the most considerable changes, but rather the coral polyps, etc.[165] He then, after dilating on the value of the study of the invertebrate animals, proceeds to define them, and closes his lecture by describing the seven cla.s.ses into which he divides this group.

II. _Recherches sur l'Organisation des Corps vivans, 1802 (Opening Discourse)._

The following is an abstract with translations of the most important pa.s.sages relating to evolution:

That the portion of the animal kingdom treated in these lectures comprises more species than all the other groups taken together is, however, the least of those considerations which should interest my hearers.

"It is the group containing the most curious forms, the richest in marvels of every kind, the most astonis.h.i.+ng, especially from the singular facts of organization that they present, though it is that hitherto the least considered under these grand points of view.

"How much better than learning the names and characters of all the species is it to learn of the origin, relation, and mode of existence of all the natural productions with which we are surrounded.

"_First Part: Progress in structure of living beings in proportion as circ.u.mstances favor them._

"When we give continued attention to the examination of the organization of different living beings, to that of different systems which this organization presents in each organic kingdom, finally to certain changes which are seen to be undergone in certain circ.u.mstances, we are convinced:

"1. That the nature of organic movement is not only to develop the organization but also to multiply the organs and to fulfil the functions, and that at the outset this organic movement continually tends to restrict to functions special to certain parts the functions which were at first general--_i.e._, common to all parts of the body;

"2. That the result of _nutrition_ is not only to supply to the developing organization what the organic movement tends to form, but besides, also by a forced inequality between the matters which are a.s.similated and those which are dissipated by losses, this function at a certain term of the duration of life causes a progressive deterioration of the organs, so that as a necessary consequence it inevitably causes death;