Quotes three paragraphs in which the reporters (Cuvier and Geoffroy St. Hilaire) say that the mummied animals of Thebes and Memphis are perfectly similar to those of to-day. Then he goes on to say:
“I have seen them, these animals, and I believe in the conformity of their resemblance with the individuals of the same species which live to-day. Thus the animals which the Egyptians worshipped and embalmed two or three thousand years ago are still in every respect similar to those which actually live in that country.
“But it would be assuredly very singular that this should be otherwise; for the position of Egypt and its climate are still or very nearly the same as at former times. Therefore the animals which live there have not been compelled to change their habits.
“There is, then, nothing in the observation which has just been reported which should be contrary to the considerations which I have expressed on this subject; and which especially proves that the animals of which it treats have existed during the whole period of nature. It only proves that they have existed for two or three thousand years; and every one who is accustomed to reflect, and at the same time to observe that which nature shows us of the monuments of its antiquity, readily appreciates the value of a duration of two or three thousand years in comparison with it.
“Hence, as I have elsewhere said, it is sure that this appearance of the stability of things in nature will always be mistaken by the average of mankind for the reality; because in general people only judge of everything relatively to themselves.
“For the man who observes, and who in this respect only judges from the changes which he himself perceives, the intervals of these changes are stationary conditions (états) which should appear to be limitless, because of the brevity of life of the individuals of his species. Thus, as the records of his observations and the notes of facts which he has consigned to his registers only extend and mount up to several thousands of years (three to five thousand years), which is an infinitely small period of time relatively to those which have sufficed to bring about the great changes which the surface of the globe has undergone, everything seems stable to him in the planet which he inhabits, and he is inclined to reject the monuments heaped up around him or buried in the earth which he treads under his feet, and which surrounds him on all sides.[174]
. . . . . . . . .
“It seems to me [as mistaken as] to expect some small creatures which only live a year, which inhabit some corner of a building, and which we may suppose are occupied with consulting among themselves as to the tradition, to pronounce on the duration of the edifice where they occur: and that going back in their paltry history to the twenty-fifth generation, they should unanimously decide that the building which serves to shelter them is eternal, or at least that it has always existed; because it has always appeared the same to them; and since they have never heard it said that it had a beginning. Great things (grandeurs) in extent and in duration are relative.[175]
“When man wishes to clearly represent this truth he will be reserved in his decisions in regard to stability, which he attributes in nature to the state of things which he observes there.[176]
“To admit the insensible change of species, and the modifications which individuals undergo as they are gradually forced to vary their habits or to contract new ones, we are not reduced to the unique consideration of too small spaces of time which our observations can embrace to permit us to perceive these changes; for, besides this induction, a quantity of facts collected for many years throws sufficient light on the question that I examine, so that does not remain undecided; and I can say now that our sciences of observation are too advanced not to have the solution sought for made evident.
“Indeed, besides what we know of the influences and the results of heteroclite fecundations, we know positively to-day that a forced and long-sustained change, both in the habits and mode of life of animals, and in the situation, soil, and climate of plants, brings about, after a sufficient time has elapsed, a very remarkable change in the individuals which are exposed to them.
“The animal which lives a free, wandering life on plains, where it habitually exercises itself in running swiftly; the birds whose needs (besoins) require them unceasingly to traverse great spaces in the air, finding themselves enclosed, some in the compartments of our menageries or in our stables, and others in our cages or in our poultry yards, are submitted there in time to striking influences, especially after a series of regenerations under the conditions which have made them contract new habits. The first loses in large part its nimbleness, its agility; its body becomes stouter, its limbs diminish in power and suppleness, and its faculties are no longer the same. The second become clumsy; they are unable to fly, and grow more fleshy in all parts of their bodies.
“Behold in our stout and clumsy horses, habituated to draw heavy loads, and which constitute a special race by always being kept together—behold, I say, the difference in their form compared with those of English horses, which are all slender, with long necks, because for a long period they have been trained to run swiftly: behold in them the influence of a difference of habit, and judge for yourselves. You find them, then, such as they are in some degree in nature. You find there our cock and our hen in the condition we have [made] them, as also the mixed races that we have formed by mixed breeding between the varieties produced in different countries, or where they were so in the state of domesticity. You find there likewise our different races of domestic pigeons, our different dogs, etc. What are our cultivated fruits, our wheat, our cabbage, our lettuce, etc., etc., if they are not the result of changes which we ourselves have effected in these plants, in changing by our culture the conditions of their situation? Are they now found in this condition in nature? To these incontestable facts add the considerations which I have discussed in my Recherches sur les Corps vivans (p. 56 et suiv.), and decide for yourselves.
“Thus, among living bodies, nature, as I have already said, offers only in an absolute way individuals which succeed each other genetically, and which descend one from the other. So the species among them are only relative, and only temporary.
“Nevertheless, to facilitate the study and the knowledge of so many different bodies it is useful to give the name of species to the entire collection of individuals which are alike, which reproduction perpetuates in the same condition as long as the conditions of their situation do not change enough to make their habits, their character, and their form vary.
“Such is, citizens, the exact sketch of that which goes on in nature since she has existed, and of that which the observation of her acts has alone enabled us to discover. I have fulfilled my object if, in presenting to you the results of my researches and of my experience, I have been able to disclose to you that which in your studies of this kind deserves your special attention.
“You now doubtless conceive how important are the considerations which I have just exposed to you, and how wrong you would be if, in devoting yourself to the study of animals or of plants, you should seek to see among them only the multiplied distinctions that we have been obliged to establish; in a word, if you should confine yourselves to fixing in your memory the variable and indefinite nomenclature which is applied to so many different bodies, instead of studying Nature herself—her course, her means, and the constant results that she knows how to attain.”
On the next fly page are the following words: Esquisse d’une Philosophie zoologique.
IV. Lamarck’s Views as published in 1806.[177]
“Those who have observed much and have consulted the great collections, have been able to convince themselves that as gradually as the circumstances of their habitat, of exposure to their surroundings, of climate, food, mode of living, etc., have changed, the characters of size, form, of proportion between the parts, of color, of consistence, of duration, of agility, and of industry have proportionately changed.
“They have been able to see, as regards the animals, that the more frequent and longer sustained use of any organ gradually strengthens this organ, develops it, enlarges it, and gives it a power proportional to the length of time it has been used; while the constant lack of use of such an organ insensibly weakens it, causes it to deteriorate, progressively diminishes its faculties, and tends to make it waste away.[178]
“Finally, it has been remarked that all that nature has made individuals to acquire or lose by the sustained influence of circumstances where their race has existed for a long time, she has preserved by heredity in the new individuals which have originated from them (elle le conserve par la génération aux nouveaux individus qui en proviennent). These verities are firmly grounded, and can only be misunderstood by those who have never observed and followed nature in her operations.
“Thus we are assured that that which is taken for species among living bodies, and that all the specific differences which distinguish these natural productions, have no absolute stability, but that they enjoy only a relative stability; which it is very important to consider in order to fix the limits which we must establish in the determination of that which we must call species.
“It is known that different places change in nature and character by reason of their position, their ‘composition’ [we should say geological structure or features], and their climate; that which is easily perceived in passing over different places distinguished by special characteristics; behold already a cause of variation for the natural productions which inhabit these different places. But that which is not sufficiently known, and even that which people refuse to believe, is that each place itself changes after a time, in exposure, in climate, in nature, and in character, although with a slowness so great in relation to our period of time that we attribute to it a perfect stability.
“Now, in either case, these changed places proportionately change the circumstances relative to the living bodies which inhabit them, and these produce again other influences on those same bodies.
“We see from this that if there are extremes in these changes there are also gradations (nuances), that is to say, steps which are intermediate, and which fill up the interval; consequently there are also gradations in the differences which distinguish that which we call species.
“Indeed, as we constantly meet with such shades (or intermediate steps) between these so-called species, we find ourselves forced to descend to the minutest details to find any distinctions; the slightest peculiarities of form, of color, of size, and often even of differences only perceived in the aspect of the individual compared with other individuals which are related to it the more by their relations, are seized upon by naturalists to establish specific differences; so that, the slightest varieties being reckoned as species, our catalogues of species grow infinitely great, and the name of the productions of nature of the most interest to us are, so to speak, buried in these enormous lists, become very difficult to find, because now the objects are mostly only determined by characters which our senses can scarcely enable us to perceive.
“Meanwhile we should remember that nothing of all this exists in nature; that she knows neither classes, orders, genera, nor species, in spite of all the foundation which the portion of the natural series which our collection contains has seemed to afford them; and that of organic or living bodies there are, in reality, only individuals, and among different races which gradually pass (nuancent) into all degrees of organization” (p. 14).
On p. 70 he speaks of the animal chain from monad to man, ascending from the most simple to the most complex. The monad is the most simple, the most like a germ of living bodies, and from its nature passes to the volvoces, proteus, vibrios; from them nature arrives at the production of “polypes rotifères”—and then at “Radiaires,” worms, Arachnida, Crustacea, and Cirripedes.
FOOTNOTES:
[162] Discours d’ouverture du Cours de Zoologie donné dans le Muséum national d’Histoire naturelle, le 21 floréal, an 8 de la République (1800). Floréal is the name adopted by the National Convention for the eighth month of the year. In the years of the Republic 1 to 7 it extended from April 20 to May 19 inclusive, and in the years 8 to 13 from April 21 to May 20 (Century Cyclopedia of Names). The lecture, then, in which Lamarck first presented his views was delivered on some day between April 21 and May 20, 1800.
[163] Lamarck by the word génération implies heredity. He nowhere uses the word hérédité.
[164] “L’oiseau que le besoin attire sur l’eau pour y trouver la proie qui le fait vivre, écarte les doigts de ses pieds lorsqu’il veut frapper l’eau et se mouvoir à sa surface” (p. 13). If the word veut has suggested the doctrine of appetency in meaning has been pushed too far by the critics of Lamarck.
[165] This he already touched upon in his Mémoires de Physique et d’Histoire naturelle (p. 342).
[166] Système des Animaux sans Vertèbres, pp. 16 and 17.
[167] I have cited the incontestable proofs in my Hydrogéologie, and I have the conviction that one day all will be compelled to accept these great truths.
[168] Ranunculus aquaticus capillaceus (Tournef., p. 291).
[169] Ranunculus aquaticus (folio rotundo et capillaceo, Tournef., p. 291).
[170] Gramen junceum, etc. (Moris, hist. 3, sec. 8, t. 9, f. 4).
[171] Discours d’ouverture d’un Cours de Zoologie, prononcé en prairial, an XI, au Muséum d’Histoire naturelle, sur la question, Qu’est-ce que l’espèce parmi les corps vivans? (1803).
[172] Recherches sur l’Organisation des Corps vivans, p. 9.
[173] “See at the end of this discourse the sketch of a Philosophie zoologique relative to this subject.” [This sketch was not added—only the title at the end of the book.]
[174] See the Annales du Muséum d’Hist. nat., IVe cahier. 1., 1802, pp. 302, 303: Mémoires sur les Fossiles des Environs de Paris, etc. He repeats in his Discours what he wrote in 1802 in the Annales.
[175] Ibid. This is repeated from the article in the Annales.
[176] Ibid. “See my Recherches sur les Corps vivans” (Appendix, p. 141).
[177] Discours d’Ouverture du Cours des Animaux sans Vertèbres, prononcé dans le Muséum d’Histoire naturelle en mai 1806. (No imprint. 8o, pp. 108.) Only the most important passages are here translated.
[178] “We know that all the forms of organs compared to the uses of these same organs are always perfectly adapted. But there is a common error in this connection, since it is thought that the forms of organs have caused their functions (en ont amené l’emploi), whereas it is easy to demonstrate by observation that it is the uses (usages) which have given origin to the forms of organs.”
CHAPTER XVII
THE “PHILOSOPHIE ZOOLOGIQUE”
Lamarck’s mature views on the theory of descent comprise a portion of his celebrated Philosophie zoologique. We will let him tell the story of creation by natural causes so far as possible in his own words.
In the avertissement, or preface, he says that his experience has led him to realize that a body of precepts and of principles relating to the study of animals and even applicable to other parts of the natural sciences would now be useful, our knowledge of zoölogical facts having, for about thirty years, made considerable progress.
After referring to the differences in structure and faculties characterizing animals of different groups, he proceeds to outline his theory, and begins by asking:
“How, indeed, can I consider the singular modification in the structure of animals, as we glance over the series from the most perfect to the least perfect, without asking how we can account for a fact so positive and so remarkable—a fact attested to me by so many proofs? Should I not think that nature has successively produced the different living beings by proceeding from the most simple to the most compound; because in ascending the animal scale from the most imperfect up to the most perfect, the organization perfects itself and becomes gradually complicated in a most remarkable way?”
This leads him to consider what is life, and he remarks (p. xv.) that it does not exist without external stimuli. The conditions necessary for the existence of life are found completely developed in the simplest organization. We are then led to inquire how this organization, by reason of certain changes, can give rise to other organisms less simple, and finally originate creatures becoming gradually more complicated, as we see in ascending the animal scale. Then employing the two following considerations, he believes he perceives the solution of the problem which has occupied his thoughts.
He then cites as factors (1) use and disuse; (2) the movement of internal fluids by which passages are opened through the cellular tissue in which they move, and finally create different organs. Hence the movement of fluids in the interior of animals, and the influence of new circumstances as animals gradually expose themselves to them in spreading into every inhabitable place, are the two general causes which have produced the different animals in the condition we now see them. Meanwhile he perceived the importance of the preservation by heredity, though he nowhere uses that word, in the new individuals reproduced of everything which the results of the life and influencing circumstances had caused to be acquired in the organization of those which have transmitted existence to them.
In the Discours préliminaire, referring to the progression in organization of animals from the simplest to man, as also to the successive acquisition of different special organs, and consequently of as many faculties as new organs obtained, he remarks:
“Then we can perceive how needs (besoins), at the outset reduced to nullity, and of which the number gradually increases, have produced the inclination (penchant) to actions fitted to satisfy it; how the actions, becoming habitual and energetic, have caused the development of the organs which execute them; how the force which excites the organic movements may, in the simplest animals, be outside of them and yet animate them; how, then, this force has been transported and fixed in the animal itself; finally, how it then has become the source of sensibility, and in the end that of acts of intelligence.
“I shall add that if this method had been followed, then sensation would not have been regarded as the general and immediate cause of organic movements, and it would not have been said that life is a series of movements which are executed in virtue of sensations received by different organs; or, in other words, that all the vital movements are the product of impressions received by the sensitive parts.[179]
“This cause seems, up to a certain point, established as regards the most perfect animals; but had it been so relatively to all living beings, they should all be endowed with the power of sensation. But it cannot be proved that this is the case with plants, and it cannot likewise be proved that it is so with all the animals known.
“But nature in creating her organisms has not begun by suddenly establishing a faculty so eminent as that of sensation: she has had the means of producing this faculty in the imperfect animals of the first classes of the animal kingdom,” referring to the Protozoa. But she has accomplished this gradually and successively. “Nature has progressively created the different special organs, also the faculties which animals enjoy.”
He remarks that though it is indispensable to classify living forms, yet that our classifications are all artificial; that species, genera, families, orders, and classes do not exist in nature—only the individuals really exist. In the third chapter he gives the old definition of species, that they are fixed and immutable, and then speaks of the animal series, saying:
“I do not mean by this to say that the existing animals form a very simple series, and especially evenly graduated; but I claim that they form a branched series,[180] irregularly graduated, and which has no discontinuity in its parts, or which, at least, has not always had, if it is true that, owing to the extinction of some species, there are some breaks. It follows that the species which terminates each branch of the general series is connected at least on one side with other species which intergrade with it” (p. 59).
He then points out the difficulty of determining what are species in certain large genera, such as Papilio, Ichneumon, etc. How new species arise is shown by observation.
“A number of facts teaches us that in proportion as the individuals of one of our species are subjected to changes in situation, climate, mode of life or habits, they thereby receive influences which gradually change the consistence and the proportions of their parts, their form, their faculties, even their structure; so that it follows that all of them after a time participate in the changes to which they have been subjected.
“In the same climate very different situations and exposures cause simple variations in the individuals occurring there; but, after the lapse of time, the continual differences of situation of the individuals of which I speak, which live and successively reproduce under the same circumstances, produce differences in them which become, in some degree, essential to their existence, so that at the end of many successive generations these individuals, which originally belonged to another species, became finally transformed into a new species distinct from the other.
“For example, should the seeds of a grass or of any other plant natural to a moist field be carried by any means at first to the slope of a neighboring hill, where the soil, although more elevated, will yet be sufficiently moist to allow the plant to live there, and if it results, after having lived there and having passed through several generations, that it gradually reaches the dry and almost arid soil of a mountain side; if the plant succeeds in living there, and perpetuates itself there during a series of generations, it will then be so changed that any botanists who should find it there would make a distinct species of it.
“The same thing happens in the case of animals which circumstances have forced to change in climate, mode of life, and habits; but in their case the influences of the causes which I have just cited need still more time than the plants to bring about notable changes in the individuals.
“The idea of embracing, under the name of species, a collection of like individuals which are perpetuated by generation, and which have remained the same as long as nature has endured, implies the necessity that the individuals of one and the same species should not cross with individuals of a different species.
“Unfortunately observation has proved, and still proves every day, that this consideration is unfounded; for hybrids, very common among plants, and the pairings which we often observe between the individuals of very different species of animals, have led us to see that the limits between these supposed constant species are not so fixed as has been imagined.
“In truth, nothing often results from these singular unions, especially if they are very ill-assorted, and then the individuals which do result from them are usually infertile; but also, when the disparities are less great, we know that the default in question does not occur.
“But this cause only suffices to create, step by step, varieties which finally become races, and which, with time, constitute what we call species.
“To decide whether the idea which is formed of the species has any real foundation, let us return to the considerations which I have already explained; they lead us to see:
“1. That all the organized bodies of our globe are true productions of Nature, which she has successively formed after the lapse of much time;
“2. That, in her course. Nature has begun, and begins over again every day, to form the simplest organisms, and that she directly creates only those, namely, which are the first germs (ébauches) of organization, which are designated by the expression of spontaneous generations;
“3. That the first germs of the animal and plant having been formed in appropriate places and circumstances, the faculties of a beginning life and of an organic movement established, have necessarily gradually developed the organs, and that with time they have diversified them, as also the parts;
“4. That the power of growth in each part of the organized body being inherent in the first created forms of life, it has given rise to different modes of multiplication and of regeneration of individuals; and that consequently the progress acquired in the composition of the organization and in the shape and diversity of the parts has been preserved;
“5. That with the aid of sufficient time, of circumstances which have been necessarily favorable, of changes of condition that every part of the earth’s surface has successively undergone—in a word, by the power which new situations and new habits have of modifying the organs of living beings, all those which now exist have been gradually formed such as we now see them;
“6. Finally, that, according to a similar order of things, living beings having undergone each of the more or less great changes in the condition of their structure and parts, that which we call a species among them has been gradually and successively so formed, having only a relative constancy in its condition, and not being as old as Nature herself.
“But, it will be said, when it is supposed that by the aid of much time and of an infinite variation in circumstances, Nature has gradually formed the different animals known to us, shall we not be stopped in this supposition by the simple consideration of the admirable diversity which we observe in the instincts of different animals, and by that of the marvels of every kind presented by their different kinds of industry?
“Shall we dare to extend the spirit of system so far as to say that it is Nature who has herself alone created this astonishing diversity of means, of contrivances, of skill, of precautions, of patience, of which the industry of animals offers us so many examples? What we observe in this respect in the simple class of insects, is it not a thousand times more than sufficient to make us realize that the limit to the power of Nature in nowise permits her to herself produce so many marvels, but to force the most obstinate philosopher to recognize that here the will of the Supreme Author of all things has been necessary, and has alone sufficed to create so many admirable things?
“Without doubt, one would be rash or, rather, wholly insensate, to pretend to assign limits to the power of the first Author of all things; but, aside from that, no one could dare to say that this infinite power could not will that which Nature even shows us it has willed”[181] (p. 67).
Referring to the alleged proof of the fixity of species brought forward by Cuvier in the Annales du Muséum d’Histoire naturelle (i., pp. 235 and 236) that the mummied birds, crocodiles, and other animals of Egypt present no differences from those now living, Lamarck says:
“It would assuredly be very singular if it were otherwise, because the position of Egypt and its climate are still almost exactly what they were at that epoch. Moreover, the birds which live there still exist under the same circumstances as they were then, not having been obliged to change their habits.
“Moreover, who does not perceive that birds, which can so easily change their situation and seek places which suit them are less subject than many other animals to the variations of local circumstances, and hence less restricted in their habits.”
He adds the fact that the animals in question have inhabited Egypt for two or three thousand years, and not necessarily from all time, and that this is not time enough for marked changes. He then gives the following definition of species, which is the best ever offered: “Species, then, have only a relative stability, and are invariable only temporarily.”
“Yet, to facilitate the study and knowledge of so many different organisms it is useful to give the name of species to every similar collection of similar individuals which are perpetuated by heredity (génération) in the same condition, so long as the circumstances of their situation do not change enough to render variable their habits, character, and form.”
He then discusses fossil species in the way already described in Chapter III. (p. 75).
The subject of the checks upon over-population by the smaller and weaker animals, or the struggle for existence, is thus discussed in Chapter IV.:
“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.