Chapter 19

"Owing to the extreme multiplication of the small species, and especially of the most imperfect animals, the multiplicity of individuals might be prejudicial to the preservation of the species, to that of the progress acquired in the improvement of the organization--in a word, to the general order, if nature had not taken precautions to keep this multiplication within due limits over which she would never pass.

"Animals devour one another, except those which live only on plants; but the latter are exposed to being devoured by the carnivorous animals.

"We know that it is the strongest and the best armed which devour the weaker, and that the larger kinds devour the smaller. Nevertheless, the individuals of a single species rarely devour each other: they war upon other races.[182]

"The multiplication of the small species of animals is so considerable, and the renewals of their generations are so prompt, that these small species would render the earth uninhabitable to the others if nature had not set a limit to their prodigious multiplication. But since they serve as prey for a multitude of other animals, as the length of their life is very limited, and as the lowering of the temperature kills them, their numbers are always maintained in proper proportions for the preservation of their races and that of others.

"As to the larger and stronger animals, they would be too dominant and injure the preservation of other races if they should multiply in too great proportions. But their races devouring each other, they would only multiply slowly and in a small number at a time; this would maintain in this respect the kind of equilibrium which should exist.

"Finally, only man, considered separately from all which is characteristic of him, seems capable of multiplying indefinitely, because his intelligence and his resources secure him from seeing his increase arrested by the voracity of any animals. He exercises over them such a supremacy that, instead of fearing the larger and stronger races of animals, he is thus rather capable of destroying them, and he continually checks their increase.

"But nature has given him numerous passions, which, unfortunately, developing with his intelligence, thus place a great obstacle to the extreme multiplication of the individuals of his species.

"Indeed, it seems as if man had taken it upon himself unceasingly to reduce the number of his fellow-creatures; for never, I do not hesitate to say, will the earth be covered with the population that it could maintain. Several of its habitable parts would always be alternately very sparsely populated, although the time for these alternate changes would be to us measureless.

"Thus by these wise precautions everything is preserved in the established order; the changes and perpetual renewals which are observable in this order are maintained within limits over which they cannot pass; the races of living beings all subsist in spite of their variations; the progress acquired in the improvement of the organization is not lost; everything which appears to be disordered, overturned, anomalous, reënters unceasingly into the general order, and even coöperates with it; and especially and always the will of the sublime Author of nature and of all existing things is invariably executed" (pp. 98-101).

In the sixth chapter the author treats of the degradation and simplification of the structure from one end to the other of the animal series, proceeding, as he says, inversely to the general order of nature, from the compound to the more simple. Why he thus works out this idea of a general degradation is not very apparent, since it is out of tune with his views, so often elsewhere expressed, of a progressive evolution from the simple to the complex, and to his own classification of the animal kingdom, beginning as it does with the simplest forms and ending with man. Perhaps, however, he temporarily adopts the prevailing method of beginning with the highest forms in order to bring out clearly the successive steps in inferiority or degradation presented in descending the animal scale.

We will glean some passages of this chapter which bear on his theory of descent. Speaking of the different kinds of aquatic surroundings he remarks:

"In the first place it should be observed that in the waters themselves she [Nature] presents considerably diversified circumstances; the fresh waters, marine waters, calm or stagnant waters, running waters or streams, the waters of warm climates, those of cold regions, finally those which are shallow and those which are very deep, offer many special circumstances, each of which acts differently on the animals living in them. Now, in a degree equal to the make-up of the organization, the races of animals which are exposed to either of these circumstances have been submitted to special influences and have been diversified by them."

He then, after referring to the general degradation of the Batrachians, touches upon the atrophy of legs which has taken place in the snakes:

"If we should consider as a result of _degradation_ the loss of legs seen in the snakes, the _Ophidia_ should be regarded as constituting the lowest order of reptiles; but it would be an error to admit this consideration. Indeed, the serpents being animals which, in order to hide themselves, have adopted the habit of gliding directly along the ground, their body has lengthened very considerably and disproportionately to its thickness. Now, elongated legs proving disadvantageous to their necessity of gliding and hiding, very short legs, being only four in number, since they are vertebrate animals, would be incapable of moving their bodies. Thus the habits of these animals have been the cause of the disappearance of their legs, and yet the _batrachians_, which have them, offer a more degraded organization, and are nearer the fishes" (p. 155).

Referring on the next page to the fishes, he remarks:--

"Without doubt their general form, their lack of a constriction between the head and the body to form a neck, and the different fins which support them in place of legs, are the results of the influence of the dense medium which they inhabit, and not that of the _dégradation_ of their organization. But this modification (_dégradation_) is not less real and very great, as we can convince ourselves by examining their internal organs; it is such as to compel us to assign to the fishes a rank lower than that of the reptiles."

He then states that the series from the lamprey and fishes to the mammals is not a regularly gradated one, and accounts for this "because the work of nature has been often changed, hindered, and diverted in direction by the influences which singularly different, even contrasted, circumstances have exercised on the animals which are there found exposed in the course of a long series of their renewed generations."

Lamarck thus accounts for the production of the radial symmetry of the medusæ and echinoderms, his _Radiaires_. At the present day this symmetry is attributed perhaps more correctly to their more or less fixed mode of life.

"It is without doubt by the result of this means which nature employs, at first with a feeble energy with _polyps_, and then with greater developments in the _Radiata_, that the radial form has been acquired; because the subtile ambient fluids, penetrating by the alimentary canal, and being expansive, have been able, by an incessantly renewed repulsion from the centre towards every point of the circumference, to give rise to this radiated arrangement of parts.

"It is by this cause that, in the Radiata, the intestinal canal, although still very imperfect, since more often it has only a single opening, is yet complicated with numerous radiating vasculiform, often ramified, appendages.

"It is, doubtless, also by this cause that in the soft Radiates, as the medusæ, etc., we observe a constant isochronic movement, movement very probably resulting from the successive intermissions between the masses of subtile fluids which penetrate into the interior of these animals and those of the same fluids which escape from it, often being spread throughout all their parts.

"We cannot say that the isochronic movements of the soft Radiates are the result of their respiration; for below the vertebrate animals nature does not offer, in that of any animal, these alternate and measured movements of inspiration and expiration. Whatever may be the respiration of Radiates, it is extremely slow, and is executed without perceptible movements" (p. 200).

_The Influence of Circumstances on the Actions and Habits of Animals._

It is in Chapter VII. that the views of Lamarck are more fully presented than elsewhere, and we therefore translate all of it as literally as possible, so as to preserve the exact sense of the author.

"We do not here have to do with a line of argument, but with the examination of a positive fact, which is more general than is supposed, and which has not received the attention it deserves, doubtless because, very often, it is quite difficult to discover. This fact consists in the influence which circumstances exert on the different organisms subjected to them.

"In truth, for a long time there has been noticed the influence of different states of our organization on our character, our propensities (_penchants_), our actions, and even our ideas; but it seems to me that no one has yet recognized that of our actions and of our habits on our organization itself. Now, as these actions and these habits entirely depend on the circumstances in which we habitually find ourselves, I shall try to show how great is the influence which these circumstances exercise on the general form, on the condition of the parts, and even on the organization of living bodies. It is therefore this very positive fact which is to be the subject of this chapter.

"If we have not had numerous occasions to plainly recognize the effects of this influence on certain organisms which we have transported under entirely new and different circumstances, and if we had not seen these effects and the changes resulting from them produced, in a way, under our very eyes, the important fact in question would have always remained unknown.

"The influence of circumstances is really continuously and everywhere active on living beings, but what renders it difficult for us to appreciate this influence is that its effects only become sensible or recognizable (especially in the animals) at the end of a long period.

"Before stating and examining the proofs of this fact, which deserves our attention, and which is very important for a zoölogical philosophy, let us resume the thread of the considerations we had begun to discuss.

"In the preceding paragraph we have seen that it is now an incontrovertible fact that, in considering the animal scale in a sense the inverse of that of nature, we find that there exists in the groups composing this scale a continuous but irregular modification (_dégradation_) in the organization of animals which they comprise, an increasing simplification in the organization of these organisms; finally, a proportionate diminution in the number of faculties of these beings.

"This fact once recognized may throw the greatest light on the very order which nature has followed in the production of all the existing animals; but it does not show why the structure of animals in its increasing complexity from the more imperfect up to the most perfect offers only an irregular gradation, whose extent presents a number of anomalies or digressions which have no appearance of order in their diversity.

"Now, in seeking for the reason of this singular irregularity in the increasing complexity of organization of animals, if we should consider the outcome of the influences that the infinitely diversified circumstances in all parts of the globe exercise on the general form, the parts, and the very organization of these animals, everything will be clearly explained.

"It will, indeed, be evident that the condition in which we find all animals is, on one side, the result of the increasing complexity of the organization which tends to form a regular gradation, and, on the other, that it is that of the influences of a multitude of very different circumstances which continually tend to destroy the regularity in the gradations of the increasing complexity of the organization.

"Here it becomes necessary for me to explain the meaning I attach to the expression _circumstances influencing the form and structure of animals_--namely, that in becoming very different they change, with time, both their form and organization by proportionate modifications.

"Assuredly, if these expressions should be taken literally, I should be accused of an error; for whatever may be the circumstances, they do not directly cause any modification in the form and structure of animals.

"But the great changes in the circumstances bring about in animals great changes in their needs, and such changes in their needs necessarily cause changes in their actions. Now, if the new needs become constant or very permanent, the animals then assume new _habits_, which are as durable as the needs which gave origin to them. We see that this is easily demonstrated and even does not need any explanation to make it clearer.

"It is then evident that a great change in circumstances having become constant in a race of animals leads these animals into new habits.

"Now, if new circumstances, having become permanent in a race of animals, have given to these animals new _habits_--that is to say, have led them to perform new actions which have become habitual--there will from this result the use of such a part by preference to that of another, and in certain cases the total lack of use of any part which has become useless.

"Nothing of all this should be considered as a hypothesis or as a mere peculiar opinion; they are, on the contrary, truths which require, in order to be made evident, only attention to and the observation of facts.

"We shall see presently by the citation of known facts which prove it, on one side that the new wants, having rendered such a part necessary, have really by the result of efforts given origin to this part, and that as the result of its sustained use it has gradually strengthened it, developed, and has ended in considerably increasing its size; on the other side we shall see that, in certain cases, the new circumstances and new wants having rendered such a part wholly useless, the total lack of use of this part has led to the result that it has gradually ceased to receive the development which the other parts of the animal obtain; that it gradually becomes emaciated and thin; and that finally, when this lack of use has been total during a long time, the part in question ends in disappearing. All this is a positive fact; I propose to give the most convincing proofs.

"In the plants, where there are no movements, and, consequently, no habits properly so called, great changes in circumstances do not bring about less great differences in the development of their parts; so that these differences originate and develop certain of them, while they reduce and cause several others to disappear. But here everything operates by the changes occurring in the nutrition of the plant, in its absorptions and transpirations, in the amount of heat, light, air, and humidity which it habitually receives; finally, in the superiority that certain of the different vital movements may assume over others.

"Between individuals of the same species, some of which are constantly well nourished, and in circumstances favorable to their entire development, while the others live under reversed circumstances, there is brought about a difference in the condition of these individuals which gradually becomes very remarkable. How many examples could I not cite regarding animals and plants, which would confirm the grounds for this view! Now, if the circumstances remain the same, rendering habitual and constant the condition of individuals badly fed, diseased, or languishing, their internal organization becomes finally modified, and reproduction between the individuals in question preserves the acquired modifications, and ends in giving rise to a race very distinct from that of the individuals which unceasingly meet with circumstances favorable to their development.

"A very dry spring-time is the cause of the grass of a field growing very slowly, remaining scraggy and puny, flowering and fruiting without growing much.

"A spring interspersed with warm days and rainy days makes the same grass grow rapidly, and the harvest of hay is then excellent.

"But if any cause perpetuates the unfavorable circumstances surrounding these plants, they vary proportionally, at first in their appearance and general condition, and finally in several particulars of their characters.

"For example, if some seed of any of the grasses referred to should be carried into an elevated place, on a dry and stony greensward much exposed to the winds, and should germinate there, the plant which should be able to live in this place would always be badly nourished, and the individuals reproduced there continuing to exist under these depressing circumstances, there would result a race truly different from that living in the field, though originating from it. The individuals of this new race would be small, scraggy, and some of their organs, having developed more than others, would then offer special proportions.

"Those who have observed much, and who have consulted the great collections, have become convinced that in proportion as the circumstances of habitat, exposure, climate, food, mode of life, etc., come to change, the characters of size, form, proportion between the parts, color, consistence, agility, and industry in the animals change proportionally.

"What nature accomplishes after a long time, we bring about every day by suddenly changing, in the case of a living plant, the circumstances under which it and all the individuals of its species exist.

"All botanists know that the plants which they transplant from their birthplace into gardens for cultivation gradually undergo changes which at last render them unrecognizable. Many plants naturally very hairy then become glabrous, or almost so; many of those which were creeping and trailing, then become erect; others lose their spines or their prickles; others still, from the woody and perennial condition which their stem possesses in a warm climate, pass, in our climate, into an herbaceous condition, and among these several are nothing more than annual plants; finally, the dimensions of their parts themselves undergo very considerable changes. These effects of changes of circumstances are so well known that botanists prefer not to describe garden plants, at least only those which have been newly cultivated.

"Is not cultivated wheat (_Triticum sativum_) only a plant brought by man into the condition in which we actually see it? Who can tell me in what country such a plant lives in a state of nature--that is to say, without being there the result of its culture in some neighboring region?

"Where occur in nature our cabbage, lettuce, etc., in the condition in which we see them in our kitchen-gardens? Is it not the same as regards a number of animals which domestication has changed or considerably modified?

"What very different races among our fowls and domestic pigeons, which we have obtained by raising them in different circumstances and in different countries, and how vainly do we now endeavor to rediscover them in nature!

"Those which are the least changed, without doubt by a more recent process of domestication, and because they do not live in a climate which is foreign to them, do not the less possess, in the condition of some of their parts, great differences produced by the habits which we have made them contract. Thus our ducks and our domestic geese trace back their type to the wild ducks and geese; but ours have lost the power of rising into the high regions of the air, and of flying over extensive regions; finally, a decided change has been wrought in the state of their parts compared with that of animals of the race from which they have descended.

"Who does not know that such a native bird, which we raise in a cage and which lives there five or six years in succession, and after that replaced in nature--namely, set free--is then unable to fly like its fellows which have always been free? The slight change of circumstance operating on this individual has only diminished its power of flight, and doubtless has not produced any change in the shape of its parts. But if a numerous series of generations of individuals of the same race should have been kept in captivity for a considerable time, there is no doubt but that even the form of the parts of these individuals would gradually undergo notable changes. For a much stronger reason, if, instead of a simple captivity constantly maintained over them, this circumstance had been at the same time accompanied by a change to a very different climate, and if these individuals by degrees had been habituated to other kinds of food, and to other kinds of movements to obtain it; certainly these circumstances, united and becoming constant, would insensibly form a new and special race.

"Where do we find, in nature, this multitude of races of _dogs_, which, as the result of domesticity to which we have reduced these animals, have been brought into their present condition? Where do we find these bull-dogs, greyhounds, water spaniels, spaniels, pug-dogs, etc., etc., races which present among themselves much greater differences than those which we admit to be specific in wild animals of the same genus?

"Without doubt, a primitive single race, very near the wolf, if it is not itself the true type, has been submitted by man, at some period, to the process of domestication. This race, which then offered no difference between its individuals, has been gradually dispersed by man into different countries, with different climates; and after a time these same individuals, having undergone the influences of their habitats, and of the different habits they were obliged to contract in each country, have undergone remarkable changes, and have formed different special races. Now, the man who, for commercial reasons or from interests of any other kind, travels a very great distance, having carried into a densely populated place, as for example a great capital, different races of dogs originated in some very distant country, then the increase of these races by heredity (_génération_) has given rise successively to all those we now know.

"The following fact proves, as regards plants, how a change in any important circumstance leads to a change in the parts of their organisms.

"So long as _Ranunculus aquatilis_ is submerged in the water, its leaves are all finely incised and the divisions hair-like; but when the stalks of this plant reach the surface of the water, the leaves which grow out in the air are wider, rounded, and simply lobed. If some feet from the same plant the roots succeed in pushing into a soil only damp, without being submerged, their stalks then are short, none of their leaves are divided into capillary divisions, which gives rise to _Ranunculus hederaceus_, which the botanists regard as a species whenever they meet with it.

"There is no doubt that as regards animals important changes in the circumstances under which they are accustomed to live do not produce alteration in their organs; for here the changes are much slower in operating than in plants, and, consequently, are to us less marked, and their cause less recognizable.

"As to the circumstances which have so much power in modifying the organs of living beings, the most influential are, doubtless, the diversity of the surroundings in which they live; but besides this there are many others which, in addition, have a considerable influence in the production of the effects in question.

"It is known that different localities change in nature and quality owing to their position, their nature, and their climate, as is easily seen in passing over different places distinguished by special features; hence we see a cause of variation for the animals and plants which live in these different places. But what we do not sufficiently know, and even what we generally refuse to believe, is that each place itself changes with time in exposure, in climate, in nature, and quality, although with a slowness so great in relation to our own continuance that we attribute to it a perfect stability.

"Now, in either case, these changed localities proportionally change the circumstances relative to the organisms which inhabit them, and the latter then give rise to other influences bearing on these same beings.

"We perceive from this that, if there are extremes in these changes, there are also gradations--namely, degrees which are intermediate and which fill the interval. Consequently there are also gradations in the differences which distinguish what we call _species_.

"It is then evident that the whole surface of the earth offers, in the nature and situation of the matters which occupy its different points, a diversity of circumstances which is throughout in relation with that of the forms and parts of animals, independent of the special diversity which necessarily results from the progress of the composition of organization in each animal.

"In each locality where animals can live, the circumstances which establish there an order of things remain for a long time the same, and really change there only with a slowness so great that man cannot directly notice them. He is obliged to consult monuments to recognize that in each one of these places the order of things that he discovers there has not always been the same, and to perceive that it will change more.

"The races of animals which live in each of these places should, then, retain their customary habits there also for a long time; hence to us seems an apparent constancy of races which we call _species_--constancy which has originated among us the idea that these races are as ancient as nature.

"But in the different points of the earth's surface which can be inhabited, nature and the situation of the places and climates constitute there, for the animals as for the plants, _different circumstances_ of all sorts of degrees. The animals which inhabit these different places should then differ from each other, not only on account of the state of nature of the organization in each race, but, besides, by reason of the habits that the individuals of each race there are forced to have; so, in proportion as he traverses the larger parts of the earth's surface the observing naturalist sees circumstances changing in a manner somewhat noticeable; he constantly sees that the species change proportionately in their characters.

"Now, the true order of things necessary to consider in all this consists in recognizing:

"1. That every slight change maintained under the circumstances where occur each race of animals, brings about in them a real change in their wants.

"2. That every change in the wants of animals necessitates in them other movements (_actions_) to satisfy the new needs, and consequently other habits.

"3. That every new want necessitating new actions to satisfy it, demands of the animal which feels it both the more frequent use of such of its parts of which before it made less use, which develops and considerably enlarges them, and the use of new parts which necessity has caused to insensibly develop in it by the effects of its inner feelings; which I shall constantly prove by known facts.

"Thus, to arrive at a knowledge of the true causes of so many different forms and so many different habits of which the known animals offer us examples, it is necessary to consider that circumstances infinitely diversified, but all slowly changing, into which the animals of each race are successively thrown, have caused, for each of them, new wants and necessarily changes in their habits. Moreover, this truth, which cannot be denied, being once recognized, it will be easy to see how the new needs have been able to be satisfied, and the new habits formed, if any attention be given to the two following laws of nature, which observation always confirms:

"_First Law._

"In every animal which has not exceeded the term of its development, the more frequent and sustained use of any organ gradually strengthens this organ, develops and enlarges it, and gives it a strength proportioned to the length of time of such use; while the constant lack of use of such an organ imperceptibly weakens it, causes it to become reduced, progressively diminishes its faculties, and ends in its disappearance.

"_Second Law._

"Everything which nature has caused individuals to acquire or lose by the influence of the circumstances to which their race may be for a long time exposed, and consequently by the influence of the predominant use of such an organ, or by that of the constant lack of use of such part, it preserves by heredity (_génération_) and passes on to the new individuals which descend from it, provided that the changes thus acquired are common to both sexes, or to those which have given origin to these new individuals.

"These are the two fundamental truths which can be misunderstood only by those who have never observed or followed nature in its operations, or only by those who allow themselves to fall into the error which I have combated.

"Naturalists having observed that the forms of the parts of animals compared with the uses of these parts are always in perfect accord, have thought that the forms and conditions of parts have caused the function; but this is a mistake, for it is easy to demonstrate by observation that it is, on the contrary, the needs and uses of organs which have developed these same parts, which have even given origin to them where they did not exist, and which consequently have given rise to the condition in which we observe them in each animal.

"If this were not so, it would have been necessary for nature to have created for the parts of animals as many forms as the diversity of circumstances in which they have to live had required, and that these forms and also the circumstances had never varied.

"This is certainly not the existing order of things, and if it were really such, we should not have the race-horses of England; we should not have our great draft horses, so clumsy and so different from the first named, for nature herself has not produced their like; we should not, for the same reason, have terrier dogs with bow legs, greyhounds so swift in running, water-spaniels, etc.; we should not have tailless fowls, fantail pigeons, etc.; finally, we could cultivate the wild plants as much as we pleased in the rich and fertile soil of our gardens without fearing to see them change by long culture.

"For a long time we have felt the force of the saying which has passed into the well-known proverb--_habits form a second nature_.

"Assuredly, if the habits and nature of each animal can never vary, the proverb is false, has no foundation, and does not apply to the instances which led to its being spoken.

"If we should seriously consider all that I have just stated, it might be thought that I had good reason when in my work entitled _Recherches sur les Corps vivans_ (p. 50) I established the following proposition:

"'It is not the organs--that is to say, the nature and form of the parts of the body of an animal--which have given rise to its habits and its special faculties; but it is, on the contrary, its habits, its manner of life, and the circumstances in which are placed the individuals from which it originates, which have, with time, brought about the form of its body, the number and condition of its organs, finally, the faculties which it enjoys.'

"If we weigh this proposition, and if we recall all the observations which nature and the state of things continually lead us to do, then its importance and its solidity will become more evident.

"Time and favorable circumstances are, as I have already said, the two principal means which nature employs to give existence to all her productions: we know that time for her has no limits, and that consequently it is ever at her disposal.

"As to the circumstances of which she has need, and which she uses still daily to cause variations in all that she continues to produce, we can say that they are, in some degree, for her inexhaustible.

"The principal circumstances arise from the influence of climate; from those of different temperatures of the atmosphere, and from all the environing media; from that of the diversity of different localities and their situation; from that of habits, the ordinary movements, the most frequent actions; finally, from that of means of preservation, of mode of living, of defence, of reproduction, etc.

"Moreover, owing to these diverse influences, the faculties increase and become stronger by use, become differentiated by the new habits preserved for long ages, and insensibly the organization, the consistence--in a word, the nature and condition of parts, as also of the organs--participate in the results of all these influences, become preserved, and are propagated by generation.

"These truths, which are only the results of the two natural laws above stated, are in every case completely confirmed by facts; they clearly indicate the course of nature in all the diversity of its products.

"But instead of contenting ourselves with generalities which might be considered as hypothetical, let us directly examine the facts, and consider, in the animals, the result of the use or disuse of their organs on the organs themselves, according to the habits that each race has been compelled to contract.

"I shall now attempt to prove that the constant lack of exercise of organs at first diminishes their faculties, gradually impoverishes them, and ends by making them disappear, or even causing them to be atrophied, if this lack of use is perpetuated for a very long time through successive generations of animals of the same race.

"I shall next prove that, on the contrary, the habit of exercising an organ, in every animal which has not attained the limit of the diminution of its faculties, not only perfects and increases the faculties of this organ, but, besides, enables it to acquire developments and dimensions which insensibly change it; so that with time it renders it very different from the same organ in another animal which exercises it much less.

"_The lack of use of an organ, become constant by the habits formed, gradually impoverishes this organ, and ends by causing it to disappear and even to destroy it._

"As such a proposition can only be admitted on proof, and not by its simple announcement, let us prove it by the citation of the leading known facts on which it is based.

"The vertebrate animals, whose plan of organization is in all nearly the same, although they offer much diversity in their parts, have jaws armed with _teeth_; moreover, those among them which circumstances have placed in the habit of swallowing their food without previous _mastication_ are exposed to the result that their teeth become undeveloped. These teeth, then, either remain concealed between the bony edges of the jaws, without appearing above, or even their gums are found to have been atrophied.

"In the baleen whales, which have been supposed to be completely deprived of teeth, M. Geoffroy has found them concealed in the jaws of the _foetus_ of this animal. This professor has also found in the birds the groove where the teeth should be situated; but they are no longer to be seen there.

"In the class even of mammals, which comprises the most perfect animals, and chiefly those in which the vertebrate plan of organization is most perfectly carried out, not only the baleen has no usable teeth, but the ant-eater (_Myrmecophaga_) is also in the same condition, whose habit of not masticating its food has been for a long time established and preserved in its race.

"The presence of eyes in the head is a characteristic of a great number of different animals, and becomes an essential part of the plan of organization of vertebrates.

"Nevertheless the mole, which owing to its habits makes very little use of vision, has only very small eyes, which are scarcely visible, since they exercise these organs to a very slight extent.

"The _Aspalax_ of Olivier (_Voyage en Egypte et en Perse_, ii. pl. 28 f. 2), which lives under ground like the mole, and which probably exposes itself still less than that animal to the light of day, has totally lost the power of sight; also it possesses only vestiges of the organ of which it is the seat; and yet these vestiges are wholly concealed under the skin and other parts which cover them, and do not permit the least access to the light.

"The _Proteus_, an aquatic reptile allied to the salamander in its structure, and which lives in the dark subterranean waters of deep caves, has, like the _Aspalax_, only vestiges of the organs of sight--vestiges which are covered and concealed in the same manner.

"We turn to a decisive consideration relative to this question.

"Light does not penetrate everywhere; consequently animals which habitually live in situations where it does not penetrate lack the occasion of exercising the organs of sight, if nature has provided them with them. Moreover, the animals which make part of the plan of organization in which _eyes_ are necessarily present, have originally had them. However, since we find them among those which are deprived of the use of this organ, and which have only vestiges concealed and covered over, it should be evident that the impoverishment and even the disappearance of these organs are the result of a constant lack of exercise.

"What proves it is that the organ of _hearing_ is never in this condition, and that we always find it in the animals when the nature of their organization should require its existence; the reason is as follows.

"The _cause of sound_, that which, moved by the shock or the vibrations of bodies, transmits to the organ of hearing the impression which it receives, penetrates everywhere, traverses all the media, and even the mass of the densest bodies: from this it results that every animal which makes a part of a plan of organization to which _hearing_ is essential, has always occasion to exercise this organ in whatever situation it lives. So, among the _vertebrate animals_ we see none deprived of their organs of hearing; but in the groups below them, when the same organs are once wanting, we do not again find them.

"It is not so with the organ of sight, for we see this organ disappear, reappear, and again disappear, in proportion to the possibility or impossibility of the animal's exercising it.

"In the _acephalous molluscs_, the great development of the mantle of these molluscs has rendered their eyes and even their head entirely useless. These organs, also forming a part of a plan of organization which should comprise them, have disappeared and atrophied from constant lack of use.

"Finally, it is a part of the plan of organization of _reptiles_, as in other vertebrate animals, to have four legs appended to their skeleton. The serpents should consequently have four, though they do not form the lowest order of reptiles, and are not so near the fishes as the batrachians (the frogs, the salamanders, etc.).

"However, the serpents having taken up the habit of gliding along the ground, and of concealing themselves in the grass, their body, owing to continually repeated efforts to elongate itself so as to pass through narrow spaces, has acquired a considerable length disproportionate to its size. Moreover, limbs would have been very useless to these animals, and consequently would not have been employed: because long legs would have interfered with their need of gliding, and very short legs, not being more than four in number, would have been incapable of moving their body. Hence the lack of use of these parts having been constant in the races of these animals, has caused the total disappearance of these same parts, although really included in the plan of organization of the animals of their class.

"Many insects which by the natural character of their order, and even of their genus, should have wings, lack them more or less completely from disuse. A quantity of Coleoptera, Orthoptera, Hymenoptera, and of Hemiptera, etc., afford examples; the habits of these animals do not require them to make use of their wings.

"But it is not sufficient to give the explanation of the cause which has brought about the condition of the organs of different animals--a condition which we see to be always the same in those of the same species; we must besides observe the changes of condition produced in the organs of one and the same individual during its life, by the single result of a great change in the special habits in the individuals of its species. The following fact, which is one of the most remarkable, will serve to prove the influence of habits on the condition of organs, and show how changes wrought in the habits of an individual, produce the condition of the organs which are brought into action during the exercise of these habits.

"M. Tenon, member of the Institute, has given an account to the Class of Sciences, that having examined the intestinal canal of several men who had been hard drinkers all their lives, he had constantly found it to be shortened to an extraordinary extent, compared with the same organ in those not given to such a habit.

"We know that hard drinkers, or those who are addicted to drunkenness, take very little solid food, that they eat very lightly, and that the beverage which they take in excess frequently suffices to nourish them.

"Moreover, as fluid aliments, especially spirituous liquors, do not remain a long time either in the stomach or in the intestines, the stomach and the remainder of the intestinal canal lose the habit of being distended in intemperate persons, so also in sedentary persons and those engaged in mental labor, who are habituated to take but little food. Gradually and at length their stomach becomes contracted, and their intestines shortened.

"We are not concerned here with the shrinkage and shortening produced by a puckering of the parts, which permit ordinary extension, if instead of a continued emptiness these viscera should be filled; the shrinkage and shortening in question are real, considerable, and such that these organs would burst open rather than yield suddenly to the causes which would require ordinary extension.

"In circumstances of persons of the same age, compare a man who, in order to devote himself to habitual study and mental work, which have rendered his digestion more difficult, has contracted the habit of eating lightly, with another who habitually takes a good deal of exercise, walks out often, and eats heartily; the stomach of the first will be weakened, and a small quantity of food will fill it, while that of the second will be not only maintained in its ordinary health but even strengthened.

"We have here the case of an organ much modified in its dimensions and in its faculties by the single cause of a change in habits during the life of the individual.

"_The frequent use of an organ become constant by habit increases the faculties of this organ, even develops it, and enables it to acquire dimensions and a power of action which it does not possess in animals which exercise less._

"We have just said that the lack of employment of an organ which necessarily exists modifies it, impoverishes it, and ends by its disappearing entirely.

"I shall now demonstrate that the continued employment of an organ, with the efforts made to draw out its powers under circumstances where it would be of service, strengthens, extends, and enlarges this organ, or creates a new one which can exercise the necessary functions.

"The bird which necessity drives to the water to find there prey fitted for its sustenance, opens the digits of its feet when it wishes to strike the water and propel itself along its surface. The skin which unites these digits at their base, by these acts of spreading apart being unceasingly repeated contracts the habit of extending; so that after a while the broad membranes which connect the digits of ducks, geese, etc., are formed as we see them. The same efforts made in swimming--_i.e._, in pushing back the water, in order to advance and to move in this liquid--have likewise extended the membrane situated between the digits of the frogs, the sea-turtles, the otter, beaver, etc.

"On the contrary, the bird whose mode of life habituates it to perch on trees, and which is born of individuals who have all contracted this habit, has necessarily the digits of the feet longer and shaped in another way than those of the aquatic animals which I have just mentioned. Its claws, after a while, became elongated, pointed, and curved or hook-like in order to grasp the branches on which the animal often rests.

"Likewise we see that the shore bird, which is not inclined to swim, and which moreover has need of approaching the edge of the water to find there its prey, is in continual danger of sinking in the mud. Now, this bird, wishing to act so that its body shall not fall into the water, makes every effort to extend and elongate its legs. It results from this that the long-continued habit that this bird and the others of its race contract, of extending and continually elongating their legs, is the _cause_ of the individuals of this race being raised as if on stilts, having gradually acquired long, naked legs, which are denuded of feathers up to the thighs and often above them (_Système des Animaux sans Vertèbres_, p. 16).

"We also perceive that the same bird, wishing to catch fish without wetting its body, is obliged to make continual efforts to lengthen its neck. Now, the results of these habitual efforts in this individual and in those of its race have enabled them, after a time, to singularly elongate them--as, indeed, is proved by the long neck of all shore birds.

"If any swimming birds, such as the swan and the goose, whose legs are short, nevertheless have a very long neck, it is because these birds in swimming on the surface of the water have the habit of plunging their head down as far as they can, to catch aquatic larvæ and different animalcules for food, and because they make no effort to lengthen their legs.

"When an animal to satisfy its wants makes repeated efforts to elongate its tongue, it will acquire a considerable length (the ant-eater, green wood-pecker); when it is obliged to seize anything with this same organ, then its tongue will divide and become forked. That of the humming-birds, which seize with their tongue, and that of the lizard and serpents, which use it to feel and examine objects in front of them, are proofs of what I advocate.

"Wants, always occasioned by circumstances, and followed by sustained efforts to satisfy them, are not limited in results, in modifying--that is to say, in increasing or diminishing--the extent and the faculties of organs; but they also come to displace these same organs when certain of these wants become a necessity.

"The fishes which habitually swim in large bodies of water, having need of seeing laterally, have, in fact, their eyes placed on the sides of the head. Their bodies, more or less flattened according to the _species_, have their sides perpendicular to the plane of the water, and their eyes are placed in such a way that there is an eye on each flattened side. But those fishes whose habits place them under the necessity of constantly approaching the shores, and especially the shelving banks or where the slope is slight, have been forced to swim on their flattened faces, so as to be able to approach nearer the edge of the water. In this situation, receiving more light from above than from beneath, and having a special need of being always attentive to what is going on above them, this need has forced one of their eyes to undergo a kind of displacement, and to assume the very singular situation which is familiar to us in the _soles_, _turbots_, _dabs_, etc. (_Pleuronectes_ and _Achirus_). The situation of these eyes is asymmetrical, because this results from an incomplete change. Now, this change is entirely completed in the rays, where the transverse flattening of the body is entirely horizontal, as also the head. Also the eyes of the rays, both situated on the upper side, have become symmetrical.

"The serpents which glide along the surface of the ground are obliged chiefly to see elevated objects, or what are above their eyes. This necessity has brought an influence to bear on the situation of the organs of vision in these animals; and, in fact, they have the eyes placed in the lateral and upper parts of the head, so as to easily perceive what is above or at their sides; but they only see for a short distance what is in front of them. Moreover, forced to supply the lack of ability to see and recognize what is in front of their head, and which might injure them, they need only to feel such objects with the aid of their tongue, which they are obliged to dart out with all their power. This habit has not only contributed to render the tongue slender, very long and retractile, but has also led in a great number of species to its division, so as to enable them to feel several objects at once; it has likewise allowed them to form an opening at the end of their head, to enable the tongue to dart out without their being obliged to open their jaws.

"Nothing is more remarkable than the result of habits in the herbivorous mammals.

"The quadruped to whom circumstances and the wants which they have created have given for a long period, as also to others of its race, the habit of browsing on grass, only walks on the ground, and is obliged to rest there on its four feet the greater part of its life, moving about very little, or only to a moderate extent. The considerable time which this sort of creature is obliged to spend each day to fill itself with the only kind of food which it requires, leads it to move about very little, so that it uses its legs only to stand on the ground, to walk, or run, and they never serve to seize hold of or to climb trees.

"From this habit of daily consuming great amounts of food which distend the organs which receive it, and of only moving about to a limited extent, it has resulted that the bodies of these animals are thick, clumsy, and massive, and have acquired a very great volume, as we see in elephants, rhinoceroses, oxen, buffaloes, horses, etc.

"The habit of standing upright on their four feet during the greater part of the day to browse has given origin to a thick hoof which envelops the extremity of the digits of their feet; and as their toes are not trained to make any movement, and because they have served no other use than as supports, as also the rest of the leg, the most of them are short, are reduced in size, and even have ended by totally disappearing. Thus in the _pachyderms_, some have five toes enveloped in horn, and consequently their foot is divided into five parts; others have only four, and still others only three. But in the _ruminants_, which seem to be the most ancient of mammals, which are limited only to standing on the ground, there are only two digits on each foot, and only a single one is to be found in the _solipedes_ (the horse, the ass).

"Moreover, among these herbivorous animals, and especially among the ruminants, it has been found that from the circumstances of the desert countries they inhabit they are incessantly exposed to be the prey of carnivorous animals, and find safety only in precipitous flight. Necessity has forced them to run swiftly; and from the habit they have thus acquired their body has become slenderer and their limbs much more delicate: we see examples in the antelopes, the gazelles, etc.

"Other dangers in our climate to which are continually exposed the deer, the roebuck, the fallow-deer, of perishing from the chase made by man, have reduced them to the same necessity, restrained them to similar habits, and have given rise to the same results.

"The ruminating animals only using their legs as supports, and not having strong jaws, which are only exercised in cutting and browsing on grass, can only fight by striking with the head, by directing against each other the _vertex_ of this part.

"In their moments of anger, which are frequent, especially among the males, their internal feelings, by their efforts, more strongly urge the fluids toward this part of their head, and it there secretes the corneous matter in some, and osseous matter mixed with corneous matter in others, which gives origin to solid protuberances; hence the origin of horns and antlers, with which most of these animals have the head armed.

"As regards habits, it is curious to observe the results in the special form and height of the giraffe (_camelopardalis_); we know that this animal, the tallest of mammals, inhabits the interior of Africa, and that it lives in localities where the earth, almost always arid and destitute of herbage, obliges it to browse on the foliage of trees, and to make continual efforts to reach it. It has resulted from this habit, maintained for a long period in all the individuals of its race, that its forelegs have become longer than the hinder ones, and that its neck is so elongated that the giraffe, without standing on its hind legs, raises its head and reaches six meters in height (almost twenty feet).

"Among the birds, the ostriches, deprived of the power of flight, and raised on very long legs, probably owe their singular conformation to analogous circumstances.

"The result of habits is as remarkable in the carnivorous mammals as it is in the herbivorous, but it presents effects of another kind.

"Indeed, those of these mammals which are habituated, as their race, both to climb as well as to scratch or dig in the ground, or to tear open and kill other animals for food, have been obliged to use the digits of their feet; moreover, this habit has favored the separation of their digits, and has formed the claws with which they are armed.

"But among the carnivores there are some which are obliged to run in order to overtake their prey; moreover, since these need and consequently have the habit of daily tearing with their claws and burying them deeply in the body of another animal, to seize and then to tear the flesh, and have been enabled by their repeated efforts to procure for these claws a size and curvature which would greatly interfere in walking or running on stony soil, it has resulted in this case that the animal has been obliged to make other efforts to draw back these too salient and curved claws which would impede it, and hence there has resulted the gradual formation of those special sheaths in which the cats, tigers, lions, etc., withdraw their claws when not in action.

"Thus the efforts in any direction whatever, maintained for a long time or made habitually by certain parts of a living body to satisfy necessities called out by nature or by circumstances, develop these parts and make them acquire dimensions and a shape which they never would have attained if these efforts had not become the habitual action of the animals which have exercised them. The observations made on all the animals known will everywhere furnish examples.

"Can any of them be more striking than that which the _kangaroo_ offers us? This animal, which carries its young in its abdominal pouch, has adopted the habit of holding itself erect, standing only on its hind feet and tail, and only changing its position by a series of leaps, in which it preserves its erect attitude so as not to injure its young.

"Let us see the result:

"1. Its fore legs, of which it makes little use, and on which it rests only during the instant when it leaves its erect attitude, have never reached a development proportionate to that of the other parts, and have remained thin, very small, and weak;

"2. The hind legs, almost continually in action, both for supporting the body and for leaping, have, on the contrary, obtained a considerable development, and have become very large and strong;

"3. Finally, the tail, which we see is of much use in supporting the animal and in the performance of its principal movements, has acquired at its base a thickness and a strength extremely remarkable.

"These well-known facts are assuredly well calculated to prove what results from the habitual use in the animals of any organ or part; and if, when there is observed in an animal an organ especially well developed, strong, and powerful, it is supposed that its habitual use has not produced it, that its continual disuse will make it lose nothing, and, finally, that this organ has always been such since the creation of the species to which this animal belongs, I will ask why our domestic ducks cannot fly like wild ducks--in a word, I might cite a multitude of examples which prove the differences in us resulting from the exercise or lack of use of such of our organs, although these differences might not be maintained in the individuals which follow them genetically, for then their products would be still more considerable.

"I shall prove, in the second part, that when the will urges an animal to any action, the organs which should execute this action are immediately provoked by the affluence of subtile fluids (the nervous fluid), which then become the determining cause which calls for the action in question. A multitude of observations prove this fact, which is now indisputable.

"It results that the multiplied repetitions of these acts of organization strengthen, extend, develop, and even create the organs which are necessary. It is only necessary attentively to observe that which is everywhere occurring to convince ourselves of the well-grounded basis of this cause of organic developments and changes.

"Moreover, every change acquired in an organ by a habit of use sufficient to have produced it is then preserved by heredity (_génération_) if it is common to the individuals which, in fecundation, unite in the reproduction of their species. Finally, this change is propagated, and thus is transmitted to all the individuals which succeed and which are submitted to the same circumstances, unless they have been obliged to acquire it by the means which have in reality created it.

"Besides, in reproductive unions the crossings between the individuals which have different qualities or forms are necessarily opposed to the continuous propagation of these qualities and these forms. We see that in man, who is exposed to so many diverse circumstances which exert an influence on him, the qualities or the accidental defects which he has been in the way of acquiring, are thus prevented from being preserved and propagated by generation. If, when some particular features of form or any defects are acquired, two individuals under this condition should always pair, they would reproduce the same features, and the successive generations being confined to such unions, a special and distinct race would then be formed. But perpetual unions between individuals which do not have the same peculiarities of form would cause all the characteristics acquired by special circumstances to disappear.

"From this we can feel sure that if distances of habitation did not separate men the intermixture by generation would cause the general characteristics which distinguish the different nations to disappear.

"If I should choose to pass in review all the classes, all the orders, all the genera, and all the species of animals which exist, I should show that the structure of individuals and their parts, their organs, their faculties, etc., etc., are in all cases the sole result of the circumstances in which each species is found to be subjected by nature and by the habits which the individuals which compose it have been obliged to contract, and which are only the product of a power primitively existing, which has forced the animals into their well-known habits.

"We know that the animal called the _ai_, or the sloth (_Bradypus tridactylus_), is throughout life in a condition so very feeble that it is very slow and limited in its movements, and that it walks on the ground with much difficulty. Its movements are so slow that it is thought that it cannot walk more than fifty steps in a day. It is also known that the structure of this animal is in direct relation with its feeble state or its inaptitude for walking; and that should it desire to make any other movements than those which it is seen to make, it could not do it.

"Therefore, supposing that this animal had received from nature its well-known organization, it is said that this organization has forced it to adopt the habits and the miserable condition it is in.

"I am far from thinking so; because I am convinced that the habits which the individuals of the race of the _ai_ were originally compelled to contract have necessarily brought their organization into its actual state.

"Since continual exposure to dangers has at some time compelled the individuals of this species to take refuge in trees and to live in them permanently, and then feed on their leaves, it is evident that then they would give up making a multitude of movements that animals which live on the ground perform.

"All the needs of the _ai_ would then be reduced to seizing hold of the branches, to creeping along them or to drawing them in so as to reach the leaves, and then to remain on the tree in a kind of inaction, so as to prevent falling. Besides, this kind of sluggishness would be steadily provoked by the heat of the climate; for in warm-blooded animals the heat urges them rather to repose than to activity.

"Moreover, during a long period of time the individuals of the race of the _ai_ having preserved the habit of clinging to trees and of making only slow and slightly varied movements, just sufficient for their needs, their organization has gradually become adapted to their new habits, and from this it will result:

"1. That the arms of these animals making continual efforts readily to embrace the branches of trees, would become elongated;

"2. That the nails of their digits would acquire much length and a hooked shape, by the continued efforts of the animal to retain its hold;

"3. That their digits never having been trained to make special movements, would lose all mobility among themselves, would become united, and would only preserve the power of bending or of straightening out all together;

"4. That their thighs, continually embracing both the trunks and the larger branches of trees, would contract a condition of habitual separation which would tend to widen the pelvis and to cause the cotyloid cavities to be directed backward;

"5. Finally, that a great number of their bones would become fused, and hence several parts of their skeleton would assume an arrangement and a figure conformed to the habits of these animals, and contrary to what would be necessary for them to have for other habits.

"Indeed, this can never be denied, because, in fact, nature on a thousand other occasions shows us, in the power exercised by circumstances on habits, and in that of the influence of habits on forms, dispositions, and the proportion of the parts of animals, truly analogous facts.

"A great number of citations being unnecessary, we now see to what the case under discussion is reduced.

"The fact is that divers animals have each, according to their genus and their species, special habits, and in all cases an organization which is perfectly adapted to these habits.

"From the consideration of this fact, it appears that we should be free to admit either one or the other of the following conclusions, and that only one of them is susceptible of proof.

"_Conclusion admitted up to this day_: Nature (or its Author), in creating the animals, has foreseen all the possible kinds of circumstances in which they should live, and has given to each species an unchanging organization, as also a form determinate and invariable in its different parts, which compels each species to live in the places and in the climate where we find it, and has there preserved its known habits.

"_My own conclusion_: Nature, in producing in succession every species of animal, and beginning with the least perfect or the simplest to end her work with the most perfect, has gradually complicated their structure; and these animals spreading generally throughout all the inhabitable regions of the globe, each species has received, through the influence of circumstances to which it has been exposed, the habits which we have observed, and the modifications in its organs which observation has shown us it possesses.

"The first of these two conclusions is that believed up to the present day--namely, that held by nearly every one; it implies, in each animal, an unchanging organization and parts which have never varied, and which will never vary; it implies also that the circumstances of the places which each species of animal inhabits will never vary in these localities; for should they vary, the same animals could not live there, and the possibility of discovering similar forms elsewhere, and of transporting them there, would be forbidden.

"The second conclusion is my own: it implies that, owing to the influence of circumstances on habits, and as the result of that of habits on the condition of the parts and even on that of the organization, each animal may receive in its parts and its organization, modifications susceptible of becoming very considerable, and of giving rise to the condition in which we find all animals.

"To maintain that this second conclusion is unfounded, it is necessary at first to prove that each point of the surface of the globe never varies in its nature, its aspect, its situation whether elevated or depressed, its climate, etc., etc.; and likewise to prove that any part of animals does not undergo, even at the end of a long period, any modification by changes of circumstances, and by the necessity which directs them to another kind of life and action than that which is habitual to them.

"Moreover, if a single fact shows that an animal for a long time under domestication differs from the wild form from which it has descended, and if in such a species in domesticity we find a great difference in conformation between the individuals submitted to such habits and those restricted to different habits, then it will be certain that the first conclusion does not conform to the laws of nature, and that, on the contrary, the second is perfectly in accord with them.

"Everything combines then to prove my assertion--namely, that it is not the form, either of the body or of its parts, which gives rise to habits, and to the mode of life among animals; but that it is on the contrary the habits, the manner of living, and all the other influencing circumstances which have, after a time, constituted the form of the body and of the parts of animals. With the new forms, new faculties have been acquired, and gradually nature has come to form the animals as we actually see them.

"Can there be in natural history a consideration more important, and to which we should give more attention, than that which I have just stated?

"We will end this first part with the principles and the exposition of the natural classification of animals."

In the fourth chapter of the third part (vol. ii. pp. 276-301) Lamarck treats of the internal feelings of certain animals, which provoke wants (_besoins_). This is the subject which has elicited so much adverse criticism and ridicule, and has in many cases led to the wholesale rejection of all of Lamarck's views. It is generally assumed or stated by Lamarck's critics, who evidently did not read his book carefully, that while he claimed that the plants were evolved by the direct action of the physical factors, that in the case of all the animals the process was indirect. But this is not correct. He evidently, as we shall see, places the lowest animals, those without (or what he supposed to be without) a nervous system, in the same category as the plants. He distinctly states at the outset that only certain animals and man are endowed with this singular faculty, "which consists in being able to experience _internal emotions_ which provoke the wants and different external or internal causes, and which give birth to the power which enables them to perform different actions."

"The nervous fluid," he says, "can, then, undergo movements in certain parts of its mass, as well as in every part at once; moreover, it is these latter movements which constitute the _general movements_ (_ébranlements_) of this fluid, and which we now proceed to consider.

"The general movements of the nervous fluid are of two kinds; namely,

"1. Partial movements (_ébranlements_), which finally become general and end in a reaction. It is the movements of this sort which produce feeling. We have treated of them in the third chapter.

"2. The movements which are general from the time they begin, and which form no reaction. It is these which constitute internal emotions, and it is of them alone of which we shall treat.

"But previously, it is necessary to say a word regarding the _feeling of existence_, because this feeling is the source from which the inner emotions originate.

"_On the Feeling of Existence._

"The feeling of existence (_sentiment d'existence_), which I shall call _inner feeling_,[183] so as to separate from it the idea of a general condition (_généralité_) which it does not possess, since it is not common to all living beings and not even to all animals, is a very obscure feeling, with which are endowed those animals provided with a nervous system sufficiently developed to give them the faculty of feeling.

"This sentiment, very obscure as it is, is nevertheless very powerful, for it is the source of inner emotions which test (_éprouvent_) the individuals possessing it, and, as the result, this singular force urges these individuals to themselves produce the movements and the actions which their wants require. Moreover this feeling, considered as a very active _motor_, only acts thus by sending to the muscles which necessarily cause these movements and actions the nervous fluid which excites them....

"Indeed, as the result of organic or vital movements which are produced in every animal, that which possesses a nervous system sufficiently developed has physical sensibility and continually receives in every inner and sensitive part impressions which continually affect it, and which it feels in general without being able to distinguish any single one.

"The sentiment of existence [consciousness] is general, since almost every sensitive part of the body shares in it. 'It constitutes this _me_ (_moi_) with which all animals, which are only sensitive, are penetrated, without perceiving it, but which those possessing a brain are able to notice, having the power of thought and of giving attention to it. Finally, it is in all the source of a power which is aroused by wants, which acts effectively only by emotion, and through which the movements and actions derive the force which produces them'....

"Finally, the inner feeling only manifests its power, and causes movements, when there exists a system for muscular movement, which is always dependent on the nervous system, and cannot take place without it."

The author then states that these emotions of the organic sense may operate in the animals and in man either without or with an act of their will.

"From what has been said, we cannot doubt but that the inner and general feeling which urges the animals possessing a nervous system fitted for feeling should be susceptible of being aroused by the causes which affect it; moreover, these causes are always the need both of satisfying hunger, of escaping dangers, of avoiding pain, of seeking pleasure, or that which is agreeable to the individual, etc.

"The emotions of the inner feeling can only be recognized by man, who alone pays attention to them, but he only perceives those which are strong, which excite his whole being, such as a view from a precipice, a tragic scene, etc."

Lamarck then divides the emotions into physical and moral, the latter arising from our ideas, thoughts--in short, our intellectual acts--in the account of which we need not follow him.

In the succeeding chapter (V.) the author dilates on the force which causes actions in animals. "We know," he says "that plants can satisfy their needs without moving, since they find their food in the environing _milieux_. But it is not the same with animals, which are obliged to move about to procure their sustenance. Moreover, most of them have other wants to satisfy, which require other kinds of movements and acts." This matter is discussed in the author's often leisurely and prolix way, with more or less repetition, which we will condense.

The lowest animals--those destitute of a nervous system--move in response to a stimulus from without. Nature has gradually created the different organs of animals, varying the structure and situation of these organs according to circumstances, and has progressively improved their powers. She has begun by borrowing from without, so to speak--from the environment--the _productive force_, both of organic movements and those of the external parts. "She has thus transported this force [the result of heat, electricity, and perhaps others (p. 307)] into the animal itself, and, finally, in the most perfect animals she has placed a great part of this force at their disposal, as I will soon show."

This force incessantly introduced into the lowest animals sets in motion the visible fluids of the body and excites the irritability of their contained parts, giving rise to different contractile movements which we observe; hence the appearance of an irresistible propensity (_penchant_) which constrains them to execute those movements which by their continuity or their repetition give rise to habits.

The most imperfect animals, such as the _Infusoria_, especially the monads, are nourished by absorption and by "an internal inhibition of absorbed matters." "They have," he says, "no power of seeking their food, they have not even the power of recognizing it, but they absorb it because it comes in contact with every side of them (_avec tous les points de leur individu_), and because the water in which they live furnishes it to them in sufficient abundance."

"These frail animals, in which the subtile fluids of the environing _milieux_ constitute the stimulating cause of the orgasm, of irritability and of organic movements, execute, as I have said, contractile movements which, provoked and varied without ceasing by this stimulating cause, facilitate and hasten the absorptions of which I have just spoken." ...

_On the Transportation of the force-producing Movements in the Interior of Animals._

"If nature were confined to the employment of its first means--namely, of a force entirely external and foreign to the animal--its work would have remained very important; the animals would have remained machines totally passive, and she would never have given origin in any of these living beings to the admirable phenomena of sensibility, of inmost feelings of existence which result therefrom, of the power of action, finally, of ideas, by which she can create the most wonderful of all, that of thought--in a word, intelligence.

"But, wishing to attain these grand results, she has by slow degrees prepared the means, in gradually giving consistence to the internal parts of animals; in differentiating the organs, and in multiplying and farther forming the fluids contained, etc., after which she has transported into the interior of these animals that force productive of movements and of actions which in truth it would not dominate at first, but which she has come to place, in great part, at their disposition when their organization should become very much more perfect.

"Indeed, from the time that the animal organization had sufficiently advanced in its structure to possess a nervous system--even slightly developed, as in insects--the animals provided with this organization were endowed with an intimate sense of their existence, and from that time the force productive of movements was conveyed into the very interior of the animal.

"I have already made it evident that this internal force which produces movements and actions should derive its origin in the intimate feeling of existence which animals with a nervous system possess, and that this feeling, solicited or aroused by needs, should then start into motion the subtile fluid contained in the nerves and carry it to the muscles which should act, this producing the actions which the needs require.

"Moreover, every want felt produces an emotion in the inner feeling of the individual which experiences it; and from this emotion of the feeling in question arises the force which gives origin to the movement of the parts which are placed in activity....

"Thus, in the animals which possess the power of acting--namely, the force productive of movements and actions--the inner feeling, which on each occasion originates this force, being excited by some need, places in action the power or force in question; excites the movement of displacement in the subtile fluid of the nerves--which the ancients called _animal spirits_; directs this fluid towards that of its organs which any want impels to action; finally makes this same fluid flow back into its habitual reservoirs when the needs no longer require the organ to act.

"The inner feeling takes the place of the _will_; for it is now important to consider that every animal which does not possess the special organ in which or by which it executes thoughts, judgments, etc., has in reality no will, does not make a choice, and consequently cannot control the movements which its inner feeling excites. _Instinct_ directs these actions, and we shall see that this direction always results from emotions of the inner feeling, in which intelligence has no part, and from the organization even which the habits have modified, in such a manner that the needs of animals which are in this category, being necessarily limited and always the same in the same species, the inner feeling and, consequently, the power of acting, always produces the same actions.

"It is not the same in animals which besides a nervous system have a brain [the author meaning the higher vertebrates], and which make comparisons, judgments, thoughts, etc. These same animals control more or less their power of action according to the degree of perfection of their brain; and although they are still strongly subjected to the results of their habits, which have modified their structure, they enjoy more or less freedom of the will, can choose, and can vary their acts, or at least some of them."

Lamarck then treats of the consumption and exhaustion of the nervous fluid in the production of animal movements, resulting in fatigue.

He next occupies himself with the origin of the inclination to the same actions, and of instinct in animals.

"The cause of the well-known phenomenon which constrains almost all animals to always perform the same acts, and that which gives rise in man to a propensity (_penchant_) to repeat every action, becoming habitual, assuredly merits investigation.

"The animals which are only 'sensible'[184]--namely, which possess no brain, cannot think, reason, or perform intelligent acts, and their perceptions being often very confused--do not reason and can scarcely vary their actions. They are, then, invariably bound by habits. Thus the insects, which of all animals endowed with feeling have the least perfect nervous system,[185] have perceptions of objects which affect them, and seem to have memory of them when they are repeated. Yet they can vary their actions and change their habits, though they do not possess the organ whose acts could give them the means.

"_On the Instincts of Animals._

"We define instinct as the sum (_ensemble_) of the decisions (_déterminations_) of animals in their actions; and, indeed, some have thought that these determinations were the product of a rational choice, and consequently the fruit of experience. Others, says Cabanis, may think with the observers of all ages that several of these decisions should not be ascribed to any kind of reasoning, and that, without ceasing as for that to have their source in physical sensibility, they are most often formed without the will of the individuals able to have any other part than in better directing the execution. It should be added, without the will having any part in it; for when it does not act, it does not, of course, direct the execution.

"If it had been considered that all the animals which enjoy the power of sensation have their inner feeling susceptible of being aroused by their needs, and that the movements of their nervous fluids, which result from these emotions, are constantly directed by this inner sentiment and by habits, then it has been felt that in all the animals deprived of intelligence all the decisions of action can never be the result of a rational choice, of judgment, of profitable experience--in a word, of will--but that they are subjected to needs which certain sensations excite, and which awaken the inclinations which urge them on.

"In the animals even which enjoy the power of performing certain intelligent acts, it is still more often the inner feeling and the inclinations originating from habits which decide, without choice, the acts which animals perform.

"Moreover, although the executing power of movements and of actions, as also the cause which directs them, should be entirely internal, it is not well, as has been done,[186] to limit to internal impressions the primary cause or provocation of these acts, with the intention to restrict to external impressions that which provokes intelligent acts; for, from what few facts are known bearing on these considerations, we are convinced that, either way, the causes which arouse and provoke acts are sometimes internal and sometimes external, that these same causes give rise in reality to impressions all of which act internally.

"According to the idea generally attached to the word _instinct_ the faculty which this word expresses is considered as a light which illuminates and guides animals in their actions, and which is with them what reason is to us. No one has shown that instinct can be a force which calls into action; that this force acts effectively without any participation of the will, and that it is constantly directed by acquired inclinations."

There are, the author states, two kinds of causes which can arouse the inner feeling (organic sense)--namely, those which depend on intellectual acts, and those which, without arising from it, immediately excite it and force it to direct its power of acting in the direction of acquired inclinations.

"These are the only causes of this last kind, which constitute all the acts of _instinct_; and as these acts are not the result of deliberation, of choice, of judgment, the actions which arise from them always satisfy, surely and without error, the wants felt and the propensities arising from habits.

"Hence, _instinct_ in animals is an inclination which necessitates that from sensations provoked while giving rise to wants the animal is impelled to act without the participation of any thought or any act of the will.

"This propensity owes to the organization what the habits have modified in its favor, and it is excited by impressions and wants which arouse the organic sense of the individual and put it in the way of sending the nervous fluid in the direction which the propensity in activity needs to the muscles to be placed in action.

"I have already said that the habit of exercising such an organ, or such a part of the body, to satisfy the needs which often spring up, should give to the subtile fluid which changes its place where is to be operated the power which causes action so great a facility in moving towards this organ, where it has been so often employed, that this habit should in a way become inherent in the nature of the individual, which is unable to change it.

"Moreover, the wants of animals possessing a nervous system being, in each case, dependent on the Structure of these organisms, are:

"1. Of obtaining any kind of food;

"2. Of yielding to sexual fecundation which excites in them certain sensations;

"3. Of avoiding pain;

"4. Of seeking pleasure or happiness.

"To satisfy these wants they contract different kinds of habits, which are transformed into so many propensities, which they can neither resist nor change. From this originate their habitual actions, and their special propensities to which we give the name of instinct.[187]

"This propensity of animals to preserve their habits and to renew the actions resulting from them being once acquired, is then propagated by means of reproduction or generation, which preserves the organization and the disposition of parts in the state thus attained, so that this same propensity already exists in the new individuals even before they have exercised it.

"It is thus that the same habits and the same _instinct_ are perpetuated from generation to generation in the different species or races of animals, without offering any notable variation,[188] so long as it does not suffer change in the circumstances essential to the mode of life."

"_On the Industry of Certain Animals._

"In those animals which have no brain that which we call _industry_ as applied to certain of their actions does not deserve such a name, for it is a mistake to attribute to them a faculty which they do not possess.

"Propensities transmitted and received by heredity (_génération_); habits of performing complicated actions, and which result from these acquired propensities; finally, different difficulties gradually and habitually overcome by as many emotions of the organic sense (_sentiment intérieur_), constitute the sum of actions which are always the same in the individuals of the same race, to which we inconsiderately give the name of _industry_.

"The instinct of animals being formed by the habit of satisfying the four kinds of wants mentioned above, and resulting from the propensities acquired for a long time which urge them on in a way determined for each species, there comes to pass, in the case of some, only a complication in the actions which can satisfy these four kinds of wants, or certain of them, and, indeed, only the different difficulties necessary to be overcome have gradually compelled the animal to extend and make contrivances, and have led it, without choice or any intellectual act, but only by the emotions of the organic sense, to perform such and such acts.

"Hence the origin, in certain animals, of different complicated actions, which has been called _industry_, and which are so enthusiastically admired, because it has always been supposed, at least tacitly, that these actions were contrived and deliberately planned, which is plainly erroneous. They are evidently the fruit of a necessity which has expanded and directed the habits of the animals performing them, and which renders them such as we observe.

"What I have just said is especially applicable to the invertebrate animals, in which there enters no act of intelligence. None of these can indeed freely vary its actions; none of them has the power of abandoning what we call its _industry_ to adopt any other kind.

"There is, then, nothing wonderful in the supposed industry of the ant-lion (_Myrmeleon formica-leo_), which, having thrown up a hillock of movable sand, waits until its booty is thrown down to the bottom of its funnel by the showers of sand to become its victim; also there is none in the manoeuvre of the oyster, which, to satisfy all its wants, does nothing but open and close its shell. So long as their organization is not changed they will always, both of them, do what we see them do, and they will do it neither voluntarily nor rationally.

"This is not the case with the vertebrate animals, and it is among them, especially in the birds and mammals, that we observe in their actions traces of a true _industry_; because in difficult cases their intelligence, in spite of their propensity to habits, can aid them in varying their actions. These acts, however, are not common, and are only slightly manifested in certain races which have exercised them more, as we have had frequent occasion to remark."

Lamarck then (chapter vi.) examines into the nature of the _will_, which he says is really the principle underlying all the actions of animals. The will, he says, is one of the results of thought, the result of a reflux of a portion of the nervous fluid towards the parts which are to act.

He compares the brain to a register on which are imprinted ideas of all kinds acquired by the individual, so that this individual provokes at will an effusion of the nervous fluid on this register, and directs it to any particular page. The remainder of the second volume (chapter vii.) is devoted to the understanding, its origin and that of ideas. The following additions relative to chapters vii. and viii. of the first part of this work are from vol. ii., pp. 451-466.

In the last of June, 1809, the menagerie of the Museum of Natural History having received a Phoca (_Phoca vitulina_), Lamarck, as he says, had the opportunity of observing its movements and habits. After describing its habits in swimming and moving on land and observing its relation to the clawed mammals, he says his main object is to remark that the seals do not have the hind legs arranged in the same direction as the axis of their body, because these animals are constrained to habitually use them to form a caudal fin, closing and widening, by spreading their digits, the paddle (_palette_) which results from their union.

"The morses, on the contrary, which are accustomed to feed on grass near the shore, never use their hind feet as a caudal fin; but their feet are united together with the tail, and cannot separate. Thus in animals of similar origin we see a new proof of the effect of habits on the form and structure of organs."

He then turns to the flying mammals, such as the flying squirrel (_Sciurus volans_, _ærobates_, _petaurista_, _sagitta_, and _volucella_), and then explains the origin of their adaptation for flying leaps.

"These animals, more modern than the seals, having the habit of extending their limbs while leaping to form a sort of _parachute_, can _only_ make a very prolonged leap when they glide down from a tree or spring only a short distance from one tree to another. Now, by frequent repetitions of such leaps, in the individuals of these races the skin of their sides is expanded on each side into a loose membrane, which connects the hind and fore legs, and which, enclosing a volume of air, prevents their sudden falling. These animals are, moreover, without membranes between the fingers and toes.

"The Galeopithecus (_Lemur volans_), undoubtedly a more ancient form but with the same habits as the flying squirrel (_Pteromys Geoff._), has the skin of the _flancs_ more ample, still more developed, connecting not only the hinder with the fore legs, but in addition the fingers and the tail with the hind feet. Moreover, they leap much farther than the flying squirrels, and even make a sort of flight.[189]

"Finally, the different bats are probably mammals still older than the Galeopithecus, in the habit of extending their membrane and even their fingers to encompass a greater volume of air, so as to sustain their bodies when they fly out into the air.

"By these habits, for so long a period contracted and preserved, the bats have obtained not only lateral membranes, but also an extraordinary elongation of the fingers of their fore feet (with the exception of the thumb), between which are these very ample membranes uniting them; so that these membranes of the hands become continuous with those of the flanks, and with those which connect the tail with the two hind feet, forming in these animals great membranous wings with which they fly perfectly, as everybody knows.

"Such is then the power of habits, which have a singular influence on the conformation of parts, and which give to the animals which have for a long time contracted certain of them, faculties not found in other animals.

"As regards the amphibious animals of which I have often spoken, it gives me pleasure to communicate to my readers the following reflections which have arisen from an examination of all the objects which I have taken into consideration in my studies, and seen more and more to be confirmed.

"I do not doubt but that the mammals have in reality originated from them, and that they are the veritable cradle (_berceau_) of the entire animal kingdom.

"Indeed, we see that the least perfect animals (and they are the most numerous) live only in the water; hence it is probable, as I have said (vol. ii., p. 85), that it is only in the water or in very humid places that nature causes and still forms, under favorable conditions, direct or spontaneous generations which have produced the simplest animalcules and those from which have successively been derived all the other animals.

"We know that the Infusoria, the polyps, and the Radiata only live in the water; that the worms even only live some in the water and others in very damp places.

"Moreover, regarding the worms, which seem to form an initial branch of the animal scale, since it is evident that the Infusoria form another branch, we may suppose that among those of them which are wholly aquatic--namely, which do not live in the bodies of other animals, such as the Gordius and many others still unknown--there are doubtless a great many different aquatic forms; and that among these aquatic worms, those which afterwards habitually expose themselves to the air have probably produced amphibious insects, such as the mosquitoes, the ephemeras, etc., etc., which have successively given origin to all the insects which live solely in the air. But several races of these having changed their habits by the force of circumstances, and having formed habits of a life solitary, retired, or hidden, have given rise to the arachnides, almost all of which also live in the air.

"Finally, those of the arachnides which have frequented the water, which have consequently become progressively habituated to live in it, and which finally cease to expose themselves to the air--this indicates the relations which, connecting the Scolopendræ to Julus, this to the Oniscus, and the last to Asellus, shrimps, etc., have caused the existence of all the Crustacea.

"The other aquatic worms which are never exposed to the air, multiplying and diversifying their races with time, and gradually making progress in the complication of their structure, have caused the formation of the Annelida, Cirripedia, and molluscs, which together form an uninterrupted portion of the animal scale.

"In spite of the considerable hiatus which we observe between the known molluscs and the fishes, the molluscs, whose origin I have just indicated, have, by the intermediation of those yet remaining unknown, given origin to the fishes, as it is evident that the latter have given rise to the reptiles.

"In continuing to consult the probabilities on the origin of different animals, we cannot doubt but that the reptiles, by two distinct branches which circumstances have brought about, have given rise on one side to the formation of birds, and on the other to that of amphibious mammals, which have given in their turn origin to all the other mammals.[190]

"Indeed, the fishes having caused the formation of Batrachia, and these of the Ophidian reptiles, both having only one auricle in the heart, nature has easily come to give a heart with a double auricle to other reptiles which constitute two special branches; finally, she has easily arrived at the end of forming, in the animals which had originated from each of these branches, a heart with two ventricles.

"Thus, among the reptiles whose heart has a double auricle, on the one side, the Chelonians seem to have given origin to the birds; if, independently of several relations which we cannot disregard, I should place the head of a tortoise on the neck of certain birds, I should perceive almost no disparity in the general physiognomy of the factitious animal; and on the other side, the saurians, especially the 'planicaudes,' such as the crocodiles, seem to have given origin to the amphibious mammals.

"If the branch of the Chelonians has given rise to birds, we can yet presume that the palmipede aquatic birds, especially the _brevipennes_, such as the penguins and the _manchots_, have given origin to the monotremes.

"Finally, if the branch of saurians has given rise to the amphibious mammals, it will be most probable that this branch is the source whence all the mammals have taken their origin.

"I therefore believe myself authorized to think that the terrestrial mammals originally descended from those aquatic mammals that we call Amphibia. Because the latter being divided into three branches by the diversity of the habits which, with the lapse of time, they have adopted, some have caused the formation of the Cetacea, others that of the ungulated mammals, and still others that of the unguiculate mammals.

"For example, those of the Amphibia which have preserved the habit of frequenting the shores differ in the manner of taking their food. Some among them accustoming themselves to browse on herbage, such as the morses and lamatines, gradually gave origin to the ungulate mammals, such as the pachyderms, ruminants, etc.; the others, such as the Phocidæ, contracting the habit of feeding on fishes and marine animals, caused the existence of the unguiculate mammals, by means of races which, while becoming differentiated, became entirely terrestrial.

"But those aquatic mammals which would form the habit of never leaving the water, and only rising to breathe at the surface, would probably give origin to the different known cetaceans. Moreover, the ancient and complete habitation of the Cetacea in the ocean has so modified their structure that it is now very difficult to recognize the source whence they have derived their origin.

"Indeed, since the enormous length of time during which these animals have lived in the depths of the sea, never using their hind feet in seizing objects, their disused feet have wholly disappeared, as also their skeleton, and even the pelvis serving as their attachment.

"The alteration which the cetaceans have undergone in their limbs, owing to the influence of the medium in which they live and the habits which they have there contracted, manifests itself also in their fore limbs, which, entirely enveloped by the skin, no longer show externally the fingers in which they end; so that they only offer on each side a fin which contains concealed within it the skeleton of a hand.

"Assuredly, the cetaceans being mammals, it entered into the plan of their structure to have four limbs like the others, and consequently a pelvis to sustain their hind legs. But here, as elsewhere, that which is lacking in them is the result of atrophy brought about, at the end of a long time, by the want of use of the parts which were useless.

"If we consider that in the Phocæ, where the pelvis still exists, this pelvis is impoverished, narrowed, and with no projections on the hips, we see that the lessened (_médiocre_) use of the hind feet of these animals must be the cause, and that if this use should entirely cease, the hind limbs and even the pelvis would in the end disappear.

"The considerations which I have just presented may doubtless appear as simple conjectures, because it is possible to establish them only on direct and positive proofs. But if we pay any attention to the observations which I have stated in this work, and if then we examine carefully the animals which I have mentioned, as also the result of their habits and their surroundings, we shall find that these conjectures will acquire, after this examination, an eminent probability.

"The following _tableau_[191] will facilitate the comprehension of what I have just stated. It will be seen that, in my opinion, the animal scale begins at least by two special branches, and that in the course of its extent some branchlets (_rameaux_) would seem to terminate in certain places.

"This series of animals beginning with two branches where are situated the most imperfect, the first of these branches received their existence only by direct or spontaneous generation.

"A strong reason prevents our knowing the changes successively brought about which have produced the condition in which we observe them; it is because we are never witnesses of these changes. Thus we see the work when done, but never watching them during the process, we are naturally led to believe that things have always been as we see them, and not as they have progressively been brought about.

"Among the changes which nature everywhere incessantly produces in her _ensemble_, and her laws remain always the same, such of these changes as, to bring about, do not need much more time than the duration of human life, are easily understood by the man who observes them; but he cannot perceive those which are accomplished at the end of a considerable time.

"If the duration of human life only extended to the length of a _second_, and if there existed one of our actual clocks mounted and in movement, each individual of our species who should look at the hour-hand of this clock would never see it change its place in the course of his life, although this hand would really not be stationary. The observations of thirty generations would never learn anything very evident as to the displacement of this hand, because its movement, only being that made during half a minute, would be too slight to make an impression; and if observations much more ancient should show that this same hand had really moved, those who should see the statement would not believe it, and would suppose there was some error, each one having always seen the hand on the same point of the dial-plate.

"I leave to my readers all the applications to be made regarding this supposition.

"_Nature_, that immense totality of different beings and bodies, in every part of which exists an eternal circle of movements and changes regulated by law; totality alone unchangeable, so long as it pleases its SUBLIME AUTHOR to make it exist, should be regarded as a whole constituted by its parts, for a purpose which its Author alone knows, and not exclusively for any one of them.

"Each part necessarily is obliged to change, and to cease to be one in order to constitute another, with interests opposed to those of all; and if it has the power of reasoning it finds this whole imperfect. In reality, however, this whole is perfect, and completely fulfils the end for which it was designed."

The last work in which Lamarck discussed the theory of descent was in his introduction to the _Animaux sans Vertèbres_. But here the only changes of importance are his four laws, which we translate, and a somewhat different phylogeny of the animal kingdom.

The four laws differ from the two given in the _Philosophie zoologique_ in his theory (the second law) accounting for the origin of a new organ, the result of a new need.

"_First law_: Life, by its proper forces, continually tends to increase the volume of every body which possesses it, and to increase the size of its parts, up to a limit which it brings about.

"_Second law_: The production of a new organ in an animal body results from the supervention of a new want (_besoin_) which continues to make itself felt, and of a new movement which this want gives rise to and maintains.

"_Third law_: The development of organs and their power of action are constantly in ratio to the employment of these organs.

"_Fourth law_: Everything which has been acquired, impressed upon, or changed in the organization of individuals, during the course of their life is preserved by generation and transmitted to the new individuals which have descended from those which have undergone those changes."

In explaining the second law he says:

"The foundation of this law derives its proof from the third, in which the facts known allow of no doubt; for, if the forces of action of an organ, by their increase, further develop this organ--namely, increase its size and power, as is constantly proved by facts--we may be assured that the forces by which it acts, just originated by a new want felt, would necessarily give birth to the organ adapted to satisfy this new want, if this organ had not before existed.

"In truth, in animals so low as not to be able to _feel_, it cannot be that we should attribute to a felt want the formation of a new organ, this formation being in such a case the product of a mechanical cause, as that of a new movement produced in a part of the fluids of the animal.

"It is not the same in animals with a more complicated structure, and which are able to _feel_. They feel wants, and each want felt, exciting their inner feeling, forthwith sets the fluids in motion and forces them towards the point of the body where an action may satisfy the want experienced. Now, if there exists at this point an organ suitable for this action, it is immediately cited to act; and if the organ does not exist, and only the felt want be for instance pressing and continuous, gradually the organ originates, and is developed on account of the continuity and energy of its employment.

"If I had not been convinced: 1, that the thought alone of an action which strongly interests it suffices to arouse the _inner feeling_ of an individual; 2, that a felt want can itself arouse the feeling in question; 3, that every emotion of _inner feeling_, resulting from a want which is aroused, directs at the same instant a mass of nervous fluid to the points to be set in activity, that it also creates a flow thither of the fluids of the body, and especially nutrient ones; that, finally, it then places in activity the organs already existing, or makes efforts for the formation of those which would not have existed there, and which a continual want would therefore render necessary--I should have had doubts as to the reality of the law which I have just indicated.

"But, although it may be very difficult to verify this law by observation, I have no doubt as to the grounds on which I base it, the necessity of its existence being involved in that of the third law, which is now well established.

"I conceive, for example, that a _gasteropod mollusc_, which, as it crawls along, finds the need of feeling the bodies in front of it, makes efforts to touch those bodies with some of the foremost parts of its head, and sends to these every time supplies of nervous fluids, as well as other fluids--I conceive, I say, that it must result from this reiterated afflux towards the points in question that the nerves which abut at these points will, by slow degrees, be extended. Now, as in the same circumstances other fluids of the animal flow also to the same places, and especially nourishing fluids, it must follow that two or more tentacles will appear and develop insensibly under those circumstances on the points referred to.

"This is doubtless what has happened to all the races of _Gasteropods_, whose wants have compelled them to adopt the habit of feeling bodies with some part of their head.

"But if there occur, among the _Gasteropods_, any races which, by the circumstances which concern their mode of existence or life, do not experience such wants, then their head remains without tentacles; it has even no projection, no traces of tentacles, and this is what has happened in the case of _Bullæa_, _Bulla_, and _Chiton_."

In the _Supplément à la Distribution générale des Animaux_ (Introduction, p. 342), concerning the real order of origin of the invertebrate classes, Lamarck proposes a new genealogical tree. He states that the order of the animal series "is far from simple, that it is branching, and seems even to be composed of several distinct series;" though farther on (p. 456) he adds:

"Je regarde _l'ordre de la production_ des animaux comme formé de deux séries distinctes.

"Ainsi, je soumets à la méditation des zoologistes l'ordre présumé de la _formation_ des animaux, tel que l'exprime le tableau suivant:"

In the matter of the origin of instinct, as in evolution in general, Lamarck appears to have laid the foundation on which Darwin's views, though he throws aside Lamarck's factors, must rest. The "inherited habit" theory is thus stated by Lamarck.

Instinct, he claims, is not common to all animals, since the lowest forms, like plants, are entirely passive under the influences of the surrounding medium; they have no wants, are automata.

"But animals with a nervous system have _wants_, _i.e._, they feel hunger, sexual desires, they desire to avoid pain or to seek pleasure, etc. To satisfy these wants they contract habits, which are gradually transformed into so many propensities which they can neither resist nor change. Hence arise habitual actions and special _propensities_, to which we give the name of _instinct_.

"These propensities are inherited and become innate in the young, so that they act instinctively from the moment of birth. Thus the same habits and instincts are perpetuated from one generation to another, with no _notable_ variations, so long as the species does not suffer change in the circumstances essential to its mode of life."

The same views are repeated in the introduction to the _Animaux sans Vertèbres_ (1815), and again in 1820, in his last work, and do not need to be translated, as they are repetitions of his previously published views in the _Philosophie zoologique_.

Unfortunately, to illustrate his thoughts on instinct Lamarck does not give us any examples, nor did he apparently observe to any great extent the habits of animals. In these days one cannot follow him in drawing a line--as regards the possession of instincts--between the lowest organisms, or Protozoa, and the groups provided with a nervous system.

_Lamarck's meaning of the word "besoins," or wants or needs._--Lamarck's use of the word wants or needs (_besoins_) has, we think, been greatly misunderstood and at times caricatured or pronounced as "absurd." The distinguished French naturalist, Quatrefages, although he was not himself an evolutionist, has protested against the way Lamarck's views have been caricatured. By nearly all authors he is represented as claiming that by simply "willing" or "desiring" the individual bird or other animal radically and with more or less rapidity changed its shape or that of some particular organ or part of the body. This is, as we have seen, by no means what he states. In no instance does he speak of an animal as simply "desiring" to modify an organ in any way. The doctrine of appetency attributed to Lamarck is without foundation. In all the examples given he intimates that owing to changes in environment, leading to isolation in a new area separating a large number of individuals from their accustomed habitat, they are driven by necessity (_besoin_) or new needs to adopt a new or different mode of life--new habits. These efforts, whatever they may be--such as attempts to fly, swim, wade, climb, burrow, etc., continued for a long time "in all the individuals of its species," or the great number forced by competition to migrate and become segregated from the others of the original species--finally, owing to the changed surroundings, affect the mass of individuals thus isolated, and their organs thus exercised in a special direction undergo a slow modification.

Even so careful a writer as Dr. Alfred R. Wallace does not quite fairly, or with exactness, state what Lamarck says, when in his classical essay of 1858 he represents Lamarck as stating that the giraffe acquired its long neck by _desiring_ to reach the foliage of the more lofty shrubs, and constantly stretching its neck for the purpose. On the contrary, he does not use the word "desiring" at all. What Lamarck does say is that--

"The giraffe lives in dry, desert places, without herbage, so that it is obliged to browse on the leaves of trees, and is continually forced to reach up to them. It results from this habit, continued for a long time in all the individuals of its species, that its fore limbs have become so elongated that the giraffe, without raising itself erect on its hind legs, raises its head and reaches six meters high (almost twenty feet)."[192]

We submit that this mode of evolution of the giraffe is quite as reasonable as the very hypothetical one advanced by Mr. Wallace;[193] _i.e._, that a variety occurred with a longer neck than usual, and these "at once secured a fresh range of pasture over the same ground as their shorter-necked companions, and on the first scarcity of food were thereby enabled to outlive them." Mr. Wallace's account also of Lamarck's general theory appears to us to be one-sided, inadequate, and misleading. He states it thus: "The hypothesis of Lamarck--that progressive changes in species have been produced by the attempts of animals to increase the development of their own organs, and thus modify their structure and habits." This is a caricature of what Lamarck really taught. Wants, needs (_besoins_), volitions, desires, are not mentioned by Lamarck in his two fundamental laws (see p. 303), and when the word _besoins_ is introduced it refers as much to the physiological needs as to the emotions of the animal resulting from some new environment which forces it to adopt new habits such as means of locomotion or of acquiring food.

It will be evident to one who has read the original or the foregoing translations of Lamarck's writings that he does not refer so much to mental desires or volitions as to those physiological wants or needs thrust upon the animal by change of circumstances or by competition; and his _besoins_ may include lust, hunger, as well as the necessity of making muscular exertions such as walking, running, leaping, climbing, swimming, or flying.

As we understand Lamarck, when he speaks of the incipient giraffe or long-necked bird as making efforts to reach up or outwards, the efforts may have been as much physiological, reflex, or instinctive as mental. A recent writer, Dr. R. T. Jackson, curiously and yet naturally enough uses the same phraseology as Lamarck when he says that the long siphon of the common clam (Mya) "was brought about by the effort to reach the surface, induced by the habit of deep burial" in its hole.[194]

On the other hand, can we in the higher vertebrates entirely dissociate the emotional and mental activities from their physiological or instinctive acts? Mr. Darwin, in his _Expressions of the Emotions in Man and Animals_, discusses in an interesting and detailed way the effects of the feelings and passions on some of the higher animals.

It is curious, also, that Dr. Erasmus Darwin went at least as far as Lamarck in claiming that the transformations of animals "are in part produced by their own exertions in consequence of their desires and aversions, of their pleasures and their pains, or of irritations or of associations."

Cope, in the final chapter of his _Primary Factors of Organic Evolution_, entitled "The Functions of Consciousness," goes to much farther extremes than the French philosopher has been accused of doing, and unhesitatingly attributes consciousness to all animals. "Whatever be its nature," he says, "the preliminary to any animal movement which is not automatic is an effort." Hence he regards effort as the immediate source of all movement, and considers that the control of muscular movements by consciousness is distinctly observable; in fact, he even goes to the length of affirming that reflex acts are the product of conscious acts, whereas it is plain enough that reflex acts are always the result of some stimulus.

Another case mentioned by Lamarck in his _Animaux sans Vertèbres_, which has been pronounced as absurd and ridiculous, and has aided in throwing his whole theory into disfavor, is his way of accounting for the development of the tentacles of the snail, which is quoted on p. 348.

This account is a very probable and, in fact, the only rational explanation. The initial cause of such structures is the intermittent stimulus of occasional contact with surrounding objects, the irritation thus set up causing a flow of the blood to the exposed parts receiving the stimuli. The general cause is the same as that concerned in the production of horns and other hard defensive projections on the heads of various animals.

In commenting on this case of the snail, Professor Cleland, in his just and discriminating article on Lamarck, says:

"However absurd this may seem, it must be admitted that, unlimited time having been once granted for organs to be developed in series of generations, the objections to their being formed in the way here imagined are only such as equally apply to the theory of their origin by natural selection.... In judging the reasonableness of the second law of Lamarck [referring to new wants, see p. 346] as compared with more modern and now widely received theories, it must be observed that it is only an extension of his third law; and that third law is a fact. The strengthening of the blacksmith's arm by use is proverbially notorious. It is, therefore, only the sufficiency of the Lamarckian hypothesis to explain the first commencement of new organs which is in question, if evolution by the mere operation of forces acting in the organic world be granted; and surely the Darwinian theory is equally helpless to account for the beginning of a new organ, while it demands as imperatively that every stage in the assumed hereditary development of an organ must have been useful.... Lamarck gave great importance to the influence of new wants acting indirectly by stimulating growth and use. Darwin has given like importance to the effects of accidental variations acting indirectly by giving advantage in the struggle for existence. The speculative writings of Darwin have, however, been interwoven with a vast number of beautiful experiments and observations bearing on his speculations, though by no means proving his theory of evolution; while the speculations of Lamarck lie apart from his wonderful descriptive labors, unrelieved by intermixture with other matters capable of attracting the numerous class who, provided they have new facts set before them, are not careful to limit themselves to the conclusions strictly deducible therefrom. But those who read the _Philosophie Zoologique_ will find how many truths often supposed to be far more modern are stated with abundant clearness in its pages." (_Encyc. Brit._, art. "Lamarck.")

COMPARATIVE SUMMARY OF THE VIEWS OF THE FOUNDERS OF THE THEORY OF EVOLUTION, WITH DATES OF PUBLICATION.

-------------+-------------+------------------------+------------+------------ |Erasmus | |Geoffroy St.|Charles Buffon |Darwin |Lamarck |Hilaire |Darwin (1761-1778). |(1790-1794). |(1801-1809-1815). |(1795-1831).|(1859). -------------+-------------+------------------------+------------+------------ | | | | All animals |All animals |All organisms arose from|Unity of |Universal possibly |derived from |germs. First germ |organization|tendency to derived from |a single |originated by |in animal |fortuitous a single |filament. |spontaneous generation. |kingdom. |variability type. | |Development from the | |assumed. | |simple to the complex. |Change of | Time, its | |Animal series not |"milieu | great length,| |continuous, but |ambiant," | stated. | |tree-like; graduated |direct. | | |from monad to man; | | Immutability | |constructed the first | | of species | |phylogenetic tree. | | stated and | | |Founded the |Struggle then denied. |Time, great |Time, great length of, |doctrine of |for |length of, |definitely postulated; |homologies. |existence. Nature |definitely |its duration practically| | advances by |demanded. |unlimited. | | gradations, | | | | passing from | |Uniformitarianism of | | one species | |Hutton and of Lyell |Founder of | to another by| |anticipated. |teratology. | imperceptible| | | | degrees. |Effects of |Effects of favorable |His embryo- | |change of |circumstances, such as |logical | Changes in |climate, |changes of environment, |studies | distribution |direct |climate, soil, food, |influenced | of land and |(briefly |temperature; direct in |his | water as |stated). |case of plants and |philosophic | causing | |lowest animals, indirect|views. | variation. | |in case of the higher | | | |animals and man. | | Effects of | | | | changes of | |Conditions of existence | | climate, | |remaining constant, | | direct. | |species do not vary and | |Competition | |vice-versa. | |strongly Effects of | | | |advocated. changes of | |Struggle for existence; | | food. | |stronger devour the | |Natural |Domesti- |weaker. Competition | |selection. Effects of |cation |stated in case of ai or |Species are | domesti- |briefly |sloth. Balance of |"different |Sexual cation. |referred to. |nature. |modifi- |selection. | | |cations of | Effects of |Effects of |Effects of use and |one and the |Effects of use. (The |use: |disuse, discussed at |same type." |use and only examples|characters |length. | |disuse (in given are the|produced by | | |some callosities |their own |Vestigial structures the| |cases). on legs of |exertions in |remains of organs | | camel, of |consequence |actively used by | | baboon, and |of their |ancestors of present | | the |desires, |forms. | | thickening by|aversions, | | | use of soles |lust, hunger,|New wants or necessities| | on man's |and security.|induced by changes of | | feet.) | |climate, habitat, etc., | | |Sexual |result in production of | | |selection, |new propensities, new | | |law of |habits, and functions. | | |battle. | | | | |Change of habits | | |Protective |originate organs; change| | |mimicry. |of functions create new | | | |organs; formation of new| | |Origin of |habits precede the | | |organs before|origin of new or | | |development |modification of organs | | |of their |already formed. | | |functions. | | | | |Geographical isolation | |Isolation |Inheritance |suggested as a factor in| |"an |of acquired |case of man. | |important |characters | | |element." |(vaguely |Swamping effects of | | |stated). |crossing. | | | | | | |Instincts |Lamarck's definition of | | |result of |species the most | | |imitation. |satisfactory yet stated.| | | | | | |Opposed |Inheritance of acquired | |Inheritance |preformation |characters. | |of acquired |views of | | |characters. |Haller and |Instinct the result of | | |Bonnet. |inherited habits. | | | | | | | |Opposed preformation | | | |views; epigenesis | | | |definitely stated and | | | |adopted. | | | | | | -------------+-------------+------------------------+------------+------------

FOOTNOTES:

[179] [Cabanis.] _Rapp. du Phys. et du Moral de l'Homme_, pp. 38 à 39, et 85.

[180] Lamarck's idea of the animal series was that of a branched one, as shown by his genealogical tree on p. 193, and he explains that the series begins at least by two special branches, these ending in branchlets. He thus breaks entirely away from the old idea of a continuous ascending series of his predecessors Bonnet and others. Professor R. Hertwig therefore makes a decided mistake and does Lamarck a great injustice in his "Zoölogy," where he states: "Lamarck, in agreement with the then prevailing conceptions, regarded the animal kingdom as a series grading from the lowest primitive animal up to man" (p. 26); and again, on the next page, he speaks of "the theory of Geoffroy St.-Hilaire and Lamarck" as having in it "as a fundamental error the doctrine of the serial arrangement of the animal world" (English Trans.). Hertwig is in error, and could never have carefully read what Lamarck did say, or have known that he was the first to throw aside the serial arrangement, and to sketch out a genealogical tree.

[181] The foregoing pages (283-286) are reprinted by the author from the _Discours_ of 1803. See pp. 266-270.

[182] Perrier thus comments on this passage: "_Ici nous sommes bien près, semble-t-il, non seulement de la lutte pour la vie telle one la concevra Darwin, mais même de la sélection naturelle. Malheureusement, au lieu de poursuivre l'idée, Lamarck aussitôt s'engage dans une autre voie_," etc. (_La Philosophie zoologique avant Darwin_, p. 81).

[183] The expression "_sentiment intérieur_" may be nearly equivalent to the "organic sense" of modern psychologists, but more probably corresponds to our word consciousness.

[184] Lamarck's division of _Animaux sensibles_ comprises the insects, arachnids, crustacea, annelids, cirrhipedes, and molluscs.

[185] Rather a strange view to take, as the brain of insects is now known to be nearly as complex as that of mammals.

[186] Richerand, _Physiologie_. vol ii. p. 151.

[187] "As all animals do not have the power of performing voluntary acts, so in like manner _instinct_ is not common to all animals: for those lacking the nervous system also want the organic sense, and can perform no instinctive acts.

"These imperfect animals are entirely passive, they do nothing of themselves, they have no wants, and nature as regards them treats them as she does plants. But as they are irritable in their parts, the means which nature employs to maintain their existence enables them to execute movements which we call actions."

It thus appears that Lamarck practically regards the lowest animals as automata, but we must remember that the line he draws between animals with and without a nervous system is an artificial one, as some of the forms which he supposed to be destitute of a nervous system are now known to possess one.

[188] It should be noticed that Lamarck does not absolutely state that there are no variations whatever in instinct. His words are much less positive: "_Sans offrer de variation notable._" This dues not exclude the fact, discovered since his time, that instincts are more or less variable, thus affording grounds for Darwin's theory of the origin of new kinds of instincts from the "accidental variation of instincts." Professor James' otherwise excellent version of Lamarck's view is inexact and misleading when he makes Lamarck say that instincts are "perpetuated _without variation_ from one generation to another, so long as the outward conditions of existence remain the same" (_The Principles of Psychology_, vol. ii., p. 678, 1890). He leaves out the word notable. The italics are ours. Farther on (p. 337), it will be seen that Lamarck acknowledges that in birds and mammals instinct is variable.

[189] It is interesting to compare with this Darwin's theory of the origin of the same animals, the flying squirrels and Galeopithecus (_Origin of Species_, 5th edition, New York, pp. 173-174), and see how he invokes the Lamarckian factors of change of "climate and vegetation" and "changing conditions of life," to originate the variations before natural selection can act. His account is a mixture of Lamarckism with the added Darwinian factors of competition and natural selection. We agree with this view, that the change in environment and competition sets the ball in motion, the work being finished by the selective process. The act of springing and the first attempts at flying also involve strong emotions and mental efforts, and it can hardly be denied that these Lamarckian factors came into continual play during the process of evolution of these flying creatures.

[190] This sagacious, though crude suggestion of the origin of birds and mammals from the reptiles is now, after the lapse of nearly a century, being confirmed by modern morphologists and palæontologists.

[191] Reproduced on page 193.

[192] This is taken from my article, "Lamarck and Neo-lamarckianism," in the _Open Court_, Chicago, February, 1897. Compare also "Darwin Wrong," etc., by R. F. Licorish, M.D., Barbadoes, 1898, reprinted in _Natural Science_, April, 1899.

[193] _Natural Selection_, pp. 41-42.

[194] _American Naturalist_, 1891, p. 17.