THEORY OF DEVELOPMENT ACCORDING TO GOETHE AND OKEN.
Scientific Insufficiency of all Conceptions of a Creation of Individual Species.—Necessity of the Counter Theories of Development.—Historical Survey of the Most Important Theories of Development.—Aristotle.—His Doctrine of Spontaneous Generation.—The Meaning of Natural Philosophy.—Goethe.—His Merits as a Naturalist.—His Metamorphosis of Plants.—His Vertebral Theory of the Skull.—His Discovery of the Mid Jawbone in Man.—Goethe’s Interest in the Dispute between Cuvier and Geoffroy St. Hilaire.—Goethe’s Discovery of the Two Organic Formative Principles, of the Conservative Principle of Specification (by Inheritance), and of the Progressive Principle of Transformation (by Adaptation).—Goethe’s Views of the Common Descent of all Vertebrate Animals, including Man.—Theory of Development according to Gottfried Reinhold Treviranus.—His Monistic Conception of Nature.—Oken.—His Natural Philosophy.—Oken’s Theory of Protoplasm.—Oken’s Theory of Infusoria (Cell Theory).—Oken’s Theory of Development.
All the different ideas which we may form of a separate and independent origin of the individual organic species by creation lead us, when logically carried out, to a so-called anthropomorphism, that is, to imagining the Creator as a man-like being, as was shown in our last chapter. The Creator becomes an organism who designs a plan, reflects upon and varies this plan, and finally forms creatures according to this plan, as a human architect would his building. If even such eminent naturalists as Linnæus, Cuvier, and Agassiz, the principal representatives of the dualistic hypothesis of creation, could not arrive at a more satisfactory view, we may take it as evidence of the insufficiency of all those conceptions which would derive the various forms of organic nature from a creation of individual species.
Some naturalists, indeed, seeing the complete insufficiency of these views, have tried to replace the idea of a personal Creator by that of an unconsciously active and creative Force of Nature; yet this expression is evidently merely an evasive phrase, as long as it is not clearly shown what this force of nature is, and how it works. Hence these attempts, also, have been absolute failures. In fact, whenever an independent origin of the different forms of animals and plants has been assumed, naturalists have found themselves compelled to fall back upon so many “acts of creation,” that is, on supernatural interferences of the Creator in the natural course of things, which in all other cases goes on without interference.
It is true that several teleological naturalists, feeling the scientific insufficiency of a supernatural “creation,” have endeavoured to save the hypothesis by wishing it to be understood that creation “is nothing else than a way of coming into being, unknown and inconceivable to us.” The eminent Fritz Müller has cut off from this sophistic evasion every chance of escape by the following striking remark:—“It is intended here only to express in a disguised manner the shamefaced confession, that they neither have, nor care to have, any opinion about the origin of species. According to this explanation of the word, we might as well speak of the creation of cholera, or syphilis, of the creation of a conflagration, or of a railway accident, as of the creation of man.” (Jenaische Zestscrift, bd. v. p. 272.)
In the face, then, of these hypotheses of creation, which are scientifically insufficient, we are forced to seek refuge in the counter-theory of development of organisms, if we wish to come to a rational conception of the origin of organisms. We are forced and obliged to do so, even if the theory of development only throws a glimmer of probability upon a mechanical, natural origin of the animal and vegetable species; but all the more if, as we shall see, this theory explains all facts simply and clearly, as well as completely and comprehensively. The theories of development are by no means, as they often falsely are represented to be, arbitrary fancies, or wilful products of the imagination, which only attempt approximately to explain the origin of this or that individual organism; but they are theories founded strictly on science, which explain in the simplest manner, from a fixed and clear point of view, the whole of organic natural phenomena, and more especially the origin of organic species, and demonstrate them to be the necessary consequences of mechanical processes in nature.
As I have already shown in the second chapter, all these theories of development coincide naturally with that general theory of the universe which is usually designated as the uniform or monistic, often also as the mechanical or causal, because it only assumes mechanical causes, or causes working by necessity (causæ efficientes), for the explanation of natural phenomena. In like manner, on the other hand, the supernatural hypotheses of creation which we have already discussed coincide completely with the opposite view of the universe, which in contrast to the former is called the twofold or dualistic, often the teleological or vital, because it traces the organic natural phenomena to final causes, acting and working for a definite purpose (causæ finales). It is this deep and intrinsic connection of the different theories of creation with the most important questions of philosophy that incites us to their closer examination.
The fundamental idea, which must necessarily lie at the bottom of all natural theories of development, is that of a gradual development of all (even the most perfect) organisms out of a single, or out of a very few, quite simple, and quite imperfect original beings, which came into existence, not by supernatural creation, but by spontaneous generation, or archigony, out of inorganic matter. In reality, there are two distinct conceptions united in this fundamental idea, but which have, nevertheless, a deep intrinsic connection—namely, first, the idea of spontaneous generation (or archigony) of the original primary beings; and secondly, the idea of the progressive development of the various species of organisms from those most simple primary beings. These two important mechanical conceptions are the inseparable fundamental ideas of every theory of development, if scientifically carried out. As it maintains the derivation of the different species of animals and plants from the simplest, common primary species, we may term it also the Doctrine of Filiation, or Theory of Descent; as there is also a change of species connected with it, it may also be termed the Transmutation Theory.
While the supernatural histories of creation must have originated thousands of years ago, in that very remote primitive age when man, first developing out of the monkey-state, began for the first time to think more closely about himself, and about the origin of the world around him, the natural theories of development, on the other hand, are necessarily of much more recent origin. These views are met with only among nations of a more matured civilization, to whom, by philosophic culture, the necessity of a knowledge of natural causes has become apparent; and even among these, only individual and specially gifted natures can be expected to have recognized the origin of the world of phenomena, as well as its course of development, as the necessary consequences of mechanical, naturally active causes. In no nation have these preliminary conditions, for the origin of a natural theory of development, ever existed in so high a degree as among the Greeks of classic antiquity. But, on the other hand, they lacked a close acquaintance with the facts of the processes and forms of nature, and, consequently, the foundation based upon experience, for a satisfactory unravelling of the problem of development. Exact investigation of nature, and the knowledge of nature founded on an experimental basis, was of course almost unknown to antiquity, as well as to the Middle Ages, and is only an acquisition of modern times. We have therefore here no special occasion to examine the natural theories of development of the various Greek philosophers, since they were wanting in the knowledge gained by experience, both of organic and inorganic nature, and since they almost always, as the consequence, lost themselves in airy speculations.
One man only must be mentioned here by way of exception,—Aristotle, the greatest and the only truly great naturalist of antiquity and the Middle Ages, one of the grandest geniuses of all time. To what a degree he stands there alone, during a period of more than two thousand years, in the region of empirico-philosophical knowledge of nature, and especially in his knowledge of organic nature, is proved to us by the precious remains of his but partially surviving works. In them many traces are found of a theory of natural development. Aristotle assumes, as a matter of certainty, that spontaneous generation was the natural manner in which the lower organic creatures came into existence. He describes animals and plants originating from matter itself, through its own original force; as, for example, moths from wool, fleas from putrid dung, wood-lice from damp wood, etc. But as the distinction of organic species, which Linnæus only arrived at two thousand years later, was unknown to him, he could form no ideas about their genealogical relations.
The fundamental notion of the theory of development, that the different species of animals and plants have been developed from a common primary species by transformation, could of course only be clearly asserted after the kinds of species themselves had become better known, and after the extinct species had been carefully examined and compared with the living ones. This was not done until the end of the last and the beginning of the present century. It was not until the year 1801 that the great Lamarck expressed the theory of development, which he, in 1809, further elaborated in his classical “Philosophie Zoologique.” While Lamarck and his countryman, Geoffroy St. Hilaire, in France, opposed Cuvier’s views, and maintained a natural development of organic species by transformation and descent, Goethe and Oken at the same time pursued the same course in Germany, and helped to establish the theory of development. As these naturalists are generally called nature-philosophers (Naturphilosophen), and as this ambiguous designation is correct in a certain sense, it appears to me appropriate here to say a few words about the correct estimate of the “Naturphilosophie.”
Although for many years in England the ideas of natural science and philosophy have been looked upon as almost equivalent, and as every truly scientific investigator of nature is most justly called there a “natural philosopher,” yet in Germany for more than half a century natural science has been kept strictly distinct from philosophy, and the union of the two into a true philosophy of nature is recognized only by the few. This misapprehension is owing to the fantastic eccentricities of earlier German natural-philosophers, such as Oken, Schelling, etc.; they believed that they were able to construct the laws of nature in their own heads, without being obliged to take their stand upon the grounds of actual experience. When the complete hollowness of their assumptions had been demonstrated, naturalists, in “the nation of thinkers,” fell into the very opposite extreme, believing that they would be able to reach the high aim of science, that is, the knowledge of truth, by the mere experience of the senses, and without any philosophical activity of thought.
From that time, but especially since 1830, most naturalists have shown a strong aversion to any general, philosophical view of nature. The real aim of natural science was now supposed to consist in the knowledge of details, and it was believed that this would be attained in the study of biology, when the forms and the phenomena of life, in all individual organisms, had become accurately known, by the help of the finest instruments and means of observation. It is true that among these strictly empirical, or so-called exact naturalists, there were always very many who rose above this narrow point of view, and sought the final aim in a knowledge of the general laws of organization. Yet the great majority of zoologists and botanists, during the thirty or forty years preceding Darwin, refused to concern themselves about such general laws; all they admitted was, that perhaps in the far distant future, when the end of all empiric knowledge should have been arrived at, when all individual animals and plants should have been thoroughly examined, naturalists might begin to think of discovering general biological laws.
If we consider and compare the most important advances which the human mind has made in the knowledge of truth, we shall soon see that it is always owing to philosophical mental operations that these advances have been made, and that the experience of the senses which certainly and necessarily precedes these operations, and the knowledge of details gained thereby, only furnish the basis for those general laws. Experience and philosophy, therefore, by no means stand in such exclusive opposition to each other as most men have hitherto supposed; they rather necessarily supplement each other. The philosopher who is wanting in the firm foundation of sensuous experience, of empirical knowledge, is very apt to arrive at false conclusions in his general speculations, which even a moderately informed naturalist can refute at once. On the other hand, the purely empiric naturalists, who do not trouble themselves about the philosophical comprehension of their sensuous experiences, and who do not strive after general knowledge, can promote science only in a very slight degree, and the chief value of their hard-won knowledge of details lies in the general results which more comprehensive minds will one day derive from them.
From a general survey of the course of biological development since Linnæus’ time, we can easily see, as Bär has pointed out, a continual vacillation between these two tendencies, at one time a prevalence of the empirical—the so-called exact—and then again of the philosophical or speculative tendency. Thus at the end of the last century, in opposition to Linnæus’ purely empirical school, a natural-philosophical reaction took place, the moving spirits of which, Lamarck, Geoffroy St. Hilaire, Goethe, and Oken, endeavoured by their mental work to introduce light and order into the chaos of the accumulated empirical raw material. In opposition to the many errors and speculations of these natural philosophers, who went too far, Cuvier then came forward, introducing a second, purely empirical period. It reached its most one-sided development between the years 1830-1860, and there now followed a second philosophical reaction, caused by Darwin’s work. Thus during the last ten years, men again have begun to endeavour to obtain a knowledge of the general laws of nature, to which, after all, all detailed knowledge of experience serves only as a foundation, and through which alone it acquires its true value. It is through philosophy alone that natural knowledge becomes a true science, that is, a philosophy of nature. (Gen. Morph. i. 63-108.)
Jean Lamarck and Wolfgang Goethe stand at the head of all the great philosophers of nature who first established a theory of organic development, and who are the illustrious fellow-workers of Darwin. I turn first to our beloved Goethe, who, among all, stands in the closest relations to us Germans. However, before I explain his special services to the theory of development, it seems to me necessary to say a few words about his importance as a naturalist in general, as it is commonly very little known.
I am sure most of my readers honour Goethe only as a poet and a man; only a few have any conception of the high value of his scientific works, and of the gigantic stride with which he advanced before his own age—advanced so much that most naturalists of that time were unable to follow him. In several passages of his scientific writings he bitterly complains of the narrow-mindedness of professed naturalists, who do not know how to value his works (who cannot see the wood for the trees), and who cannot rouse themselves to discover the general laws of nature among the mass of details. He is only too just when he utters the reproach—“The philosophers will very soon discover that observers rarely rise to a stand-point from which they can survey so many important objects.” It is true, at the same time, that their want of appreciation was caused by the false road into which Goethe was led in his theory of colours.
This theory of colours, which he himself designates as the favourite production of his leisure, however much that is beautiful it may contain, is a complete failure in regard to its foundations. The exact mathematical method by means of which alone it is possible, in inorganic sciences, but above all in physics, to raise a structure step by step on a thoroughly firm basis, was altogether repugnant to Goethe. In rejecting it he allowed himself not only to be very unjust towards the most eminent physicists, but to be led into errors which have greatly injured the fame of his other valuable works. It is quite different in the organic sciences, in which we are but rarely able to proceed, from the beginning, upon a firm mathematical basis; we are rather compelled, by the infinitely difficult and intricate nature of the problem, at the first to form inductions—that is, we are obliged to endeavour to establish general laws by numerous individual observations, which are not quite complete. A comparison of kindred series of phenomena, or the method of combination, is here the most important instrument for inquiry, and this method was applied by Goethe with as much success as with conscious knowledge of its value, in his works relating to the philosophy of nature.
The most celebrated among Goethe’s writings relating to organic nature is his Metamorphosis of Plants, which appeared in 1790, a work which distinctly shows a grasp of the fundamental idea of the theory of development, inasmuch as Goethe, in it, was labouring to point out a single organ, by the infinitely varied development and metamorphosis of which the whole of the endless variety of forms in the world of plants might be conceived to have arisen; this fundamental organ he found in the leaf. If at that time the microscope had been generally employed, if Goethe had examined the structure of organisms by the means of the microscope he would have gone still further, and would have seen that the leaf is itself a compound of individual parts of a lower order, that is, of cells. He would then not have declared that the leaf, but that the cell is the real fundamental organ by the multiplication, transformation, and combination (synthesis) of which, in the first place, the leaf is formed; and that, in the next place, by transformation, variation, and combination of leaves there arise all the varied beauties in form and colour which we admire in the green parts, as well as in the organs of propagation, or the flowers of plants. Goethe here showed that in order to comprehend the whole of the phenomena, we must in the first place compare them, and, secondly, search for a simple type, a simple fundamental form, of which all other forms are only infinite variations.
Something similar to what he had here done for the metamorphosis of plants he then did for the Vertebrate animals, in his celebrated vertebral theory of the skull. Goethe was the first to show, independently of Oken, who almost simultaneously arrived at the same thought, that the skull of man and of all Vertebrate animals, in particular mammals, is nothing more than a bony case, formed of the same bones,—that is, vertebræ,—out of which the spine also is composed. The vertebræ of the skull are like those of the spine, bony rings lying behind each other, but in the skull are peculiarly changed and specialized (differentiated). Although this idea has been strongly modified by recent discoveries, yet in Goethe’s day it was one of the greatest advances in comparative anatomy, and was not only one of the first advances towards the understanding of the structure of Vertebrate animals, but at the same time explained many individual phenomena. When two parts of a body, such as the skull and spine, which appear at first sight so different, were proved to be parts originally the same, developed out of one and the same foundation, one of the difficult problems of the philosophy of nature was solved. Here again we meet the notion of a single type—the conception of a single principle, which becomes infinitely varied in the different species, and in the parts of individual species.
But Goethe did not merely endeavour to search for such far-reaching laws, he also occupied himself most actively for a long time with numerous individual researches, especially in comparative anatomy. Among these, none is perhaps more interesting than the discovery of the mid jawbone in man. As this is, in several respects, of importance to the theory of development, I shall briefly explain it here. There exist in all mammals two little bones in the upper jaw, which meet in the centre of the face, below the nose, and which lie between the two halves of the real upper jawbone. These two bones, which hold the four upper cutting teeth, are recognized without difficulty in most mammals; in man, however, they were at that time unknown, and celebrated comparative anatomists even laid great stress upon this want of a mid jawbone, as they considered it to constitute the principal difference between men and apes—the want of a mid jawbone was, curiously enough, looked upon as the most human of all human characteristics. But Goethe could not accept the notion that man, who in all other corporeal respects was clearly only a mammal of higher development, should lack this mid jawbone.
By the general law of induction as to the mid jawbone he arrived at the special deductive conclusion that it must exist in man also, and Goethe did not rest until, after comparing a great number of human skulls, he really found the mid jawbone. In some individuals it is preserved throughout a whole lifetime, but usually at an early age it coalesces with the neighbouring upper jawbone, and is therefore only to be found as an independent bone in very youthful skulls. In human embryos it can now be pointed out at any moment. In man, therefore, the mid jawbone actually exists, and to Goethe the honour is due of having first firmly established this fact, so important in many respects; and this he did while opposed by the celebrated anatomist, Peter Camper, one of the most important professional authorities. The way by which Goethe succeeded in establishing this fact is especially interesting; it is the way by which we continually advance in biological science, namely, by way of induction and deduction. Induction is the inference of a general law from the observation of numerous individual cases; deduction, on the other hand, is an inference from this general law applied to a single case which has not yet been actually observed. From the collected empirical knowledge of those days, the inductive conclusion was arrived at that all mammals had mid jawbones. Goethe drew from this the deductive conclusion, that man, whose organization was in all other respects not essentially different from mammals, must also possess this mid jawbone; and on close examination it was actually found. The deductive conclusion was confirmed and verified by experience.
Even these few remarks may serve to show the great value which we must ascribe to Goethe’s biological researches. Unfortunately most of his labours devoted to this subject are so hidden in his collected works, and his most important observations and remarks so scattered in numerous individual treatises—devoted to other subjects—that it is difficult to find them out. It also sometimes happens that an excellent, truly scientific remark is so much interwoven with a mass of useless philosophical fancies, that the latter greatly detract from the former.
Nothing is perhaps more characteristic of the extraordinary interest which Goethe took in the investigation of organic nature than the lively way in which, even in his last years, he followed the dispute which broke out in France between Cuvier and Geoffroy de St. Hilaire. Goethe, in a special treatise which was only finished a few days before his death, in March, 1832, has given an interesting description of this remarkable dispute and its general importance, as well as an excellent sketch of the two great opponents. This treatise bears the title “Principes de Philosophic Zoologique par M. Geoffroy de Saint Hilaire”; it is Goethe’s last work, and forms the conclusion of the collected edition of his works. The dispute itself was, in several respects, of the highest interest. It turned essentially upon the justification of the theory of development. It was carried on, moreover, in the bosom of the French Academy, by both opponents, with a personal vehemence almost unheard of in the dignified sessions of that learned body; this proved that both naturalists were fighting for their most sacred and deepest convictions. The conflict began on the 22nd of February, and was followed by several others; the fiercest took place on the 19th of July, 1830. Geoffroy, as the chief of the French nature-philosophers, represented the theory of natural development and the monistic conception of nature. He maintained the mutability of organic species, the common descent of the individual species from common primary forms, and the unity of their organization—or the unity of the plan of structure, as it was then called.
Cuvier was the most decided opponent of these views, and according to what we have seen, it could not be otherwise. He endeavoured to show that the nature-philosophers had no right to rear such comprehensive conclusions on the basis of the empirical knowledge then possessed, and that the unity of organization—or plan of structure of organisms—as maintained by them, did not exist. He represented the teleological (dualistic) conception of nature, and maintained that “the immutability of species was a necessary condition for the existence of a scientific history of nature,” Cuvier had the great advantage over his opponent, that he was able to bring towards the proof of his assertions things obvious to the eye; these, however, were only individual facts taken out of their connection with others. Geoffroy was not able to prove the higher and general connection of individual phenomena which he maintained, by equally tangible details. Hence Cuvier, in the eyes of the majority, gained the victory, and decided the defeat of the nature-philosophy and the supremacy of the strictly empiric tendency for the next thirty years.
Goethe of course supported Geoffroy’s views. How deeply interested he was, even in his 81st year, in this great contest is proved by the following anecdote related by Soret:—
“Monday, Aug. 2nd, 1830.—The news of the outbreak of the revolution of July arrived in Weimar to-day, and has caused general excitement. In the course of the afternoon I went to Goethe.‘Well?’ he exclaimed as I entered, ‘what do you think of this great event? The volcano has burst forth, all is in flames, and there are no more negotiations behind closed doors.’ ‘A dreadful affair,’ I answered; ‘but what else could be expected under the circumstances, and with such a ministry, except that it would end in the expulsion of the present royal family?’ ‘We do not seem to understand each other, my dear friend,’ replied Goethe. ‘I am not speaking of those people at all; I am interested in something very different, I mean the dispute between Cuvier and Geoffroy de Saint Hilaire, which has broken out in the Academy, and which is of such great importance to science.’ This remark of Goethe’s came upon me so unexpectedly, that I did not know what to say, and my thoughts for some minutes seemed to have come to a complete standstill. ‘The affair is of the utmost importance,’ he continued, ‘and you cannot form any idea of what I felt on receiving the news of the meeting on the 19th. In Geoffroy de Saint Hilaire we have now a mighty ally for a long time to come. But I see also how great the sympathy of the French scientific world must be in this affair, for, in spite of the terrible political excitement, the meeting on the 19th was attended by a full house. The best of it is, however, that the synthetic treatment of nature, introduced into France by Geoffroy, can now no longer be stopped. This matter has now become public through the discussions in the Academy, carried on in the presence of a large audience; it can no longer be referred to secret committees, or be settled or suppressed behind closed doors.’”
In my book on “The General Morphology of Organisms” I have placed as headings to the different books and chapters a selection of the numerous interesting and important sentences in which Goethe clearly expresses his view of organic nature and its constant development. I will here quote a passage from the poem entitled, “The Metamorphosis of Animals” (1819).
“All members develop themselves according to eternal laws, And the rarest form mysteriously preserves the primitive type, Form therefore determines the animal’s way of life, And in turn the way of life powerfully reacts upon all form. Thus the orderly growth of form is seen to hold Whilst yielding to change from externally acting causes.”[3]
Here, clearly enough, the contrast between two different organic constructive forms is intimated, which are opposed to one another, and which by their interaction determine the form of the organism; on the one hand, a common inner original type, firmly maintaining itself, constitutes the foundation of the most different forms; on the other hand, the externally active influence of surroundings and mode of life, which influence the original type and transform it. This contrast is still more definitely pointed out in the following passage:—
“An inner original community forms the foundation of all organization; the variety of forms, on the other hand, arises from the necessary relations to the outer world, and we may therefore justly assume an original difference of conditions, together with an uninterruptedly progressive transformation, in order to be able to comprehend the constancy as well as the variations of the phenomena of form.”
The “original type” which constitutes the foundation of every organic form “as the inner original community” is the inner constructive force, which receives the original direction of form-production—that is, the tendency to give rise to a particular form—and is propagated by Inheritance. The “uninterruptedly progressive transformation,” on the other hand, which “springs from the necessary relations to the outer world,” acting as an external formative force, produces, by Adaptation to the surrounding conditions of life, the “infinite variety of forms” (Gen. Morph. i. 154; ii. 224). The internal formative tendency of Inheritance, which retains the unity of the original type, is called by Goethe in another passage the centripetal force of the organism, or its tendency to specification; in contrast with this he calls the external formative tendency of Adaptation, which produces the variety of organic forms, the centrifugal force of organisms, or their tendency to variation. The passage in which he clearly indicates the “equilibrium” of these two extremely important organic formative tendencies, runs as follows: “The idea of metamorphosis resembles the vis centrifuga, and would lose itself in the infinite, if a counterpoise were not added to it: I mean the tendency to specification, the strong power to preserve what once has come into being, a vis centripeta, which in its deepest foundation cannot be affected by anything external.”
Metamorphosis, according to Goethe, consists not merely, as the word is now generally understood, in the changes of form which the organic individual experiences during its individual development, but, in a wider sense, in the transformation of organic forms in general. His idea of metamorphosis is almost synonymous with the theory of development. This is clear, among other things, from the following passage:—“The triumph of physiological metamorphosis manifests itself where the whole separates and transforms itself into families, the families into genera, the genera into species, and then again into other varieties down to the individual. This operation of nature goes on ad infinitum; she cannot rest inactive, but neither can she keep and preserve all that she has produced. From seeds there are always developed varying plants, exhibiting the relations of their parts to one another in an altered manner.”
Goethe had, in truth, discovered two great mechanical forces of nature, which are the active causes of organic formations, his two organic formative tendencies—on the one hand the conservative, centripetal, and internal formative tendency of Inheritance or specification; and on the other hand the progressive, centrifugal, and external formative tendency of Adaptation, or metamorphosis. This profound biological intuition could not but lead him naturally to the fundamental idea of the Doctrine of Filiation, that is, to the conception that the organic species resembling one another in form are actually related by blood, and that they are descended from a common original type. In regard to the most important of all animal groups, namely that of Vertebrate animals, Goethe expresses this doctrine in the following passage (1796):—“Thus much then we have gained, that we may assert without hesitation that all the more perfect organic natures, such as fishes, amphibious animals, birds, mammals, and man at the head of the last, were all formed upon one original type, which only varies more or less in parts which are none the less permanent, and still daily changes and modifies its form by propagation.”
This sentence is of interest in more than one way. The theory that all “the more perfect organic natures,” that is all Vertebrate animals, are descended from one common prototype, that they have arisen from it by propagation (Inheritance) and transformation (Adaptation), may be distinctly inferred. But it is especially interesting to observe that Goethe admits no exceptional position for man, but rather expressly includes him in the tribe of the other Vertebrate animals. The most important special inference of the Doctrine of Filiation, that man is descended from other Vertebrate animals, may here be recognized in the germ.[(3)]
This exceedingly important fundamental idea is expressed by Goethe still more clearly in another passage (1807), in the following words:—“If we consider plants and animals in their most imperfect condition, they can scarcely be distinguished. But this much we can say, that the creatures which by degrees emerge as plants and animals out of a common phase, where they are barely distinguishable, arrive at perfection in two opposite directions; so that the plant in the end reaches its highest glory in the tree, which is immovable and stiff, the animal in man, who possesses the greatest elasticity and freedom.” This remarkable passage not only indicates most explicitly the genealogical relationship between the vegetable and animal kingdoms, but contains the germ of the monophyletic hypothesis of descent, the importance of which I shall have to explain hereafter. (Compare Chapter XVI. and the Pedigree, p. 398.)
At the time when Goethe in this way sketched the fundamental features of the Theory of Descent, another German philosopher, Gottfried Reinhold Treviranus, of Bremen (born 1776, died 1837), was zealously engaged at the same work. As Wilhelm Focke has recently shown, Treviranus, even in the earliest of his greater works, “The Biology or Philosophy of Animate Nature,” which appeared at the beginning of the present century, had already developed monistic views of the unity of nature, and of the genealogical connection of the species of organisms, which entirely correspond with our present view of the matter. In the first three volumes of the Biology, which appeared successively in 1802, 1803, and 1805 (therefore several years before Oken’s and Lamarck’s principal works), we find numerous passages which are of interest in this respect. I shall here quote only a few of the most important.
In speaking of the principal question of our theory, the question of the origin of organic species, Treviranus makes the following remarks:—“Every form of life can be produced by physical forces in one of two ways: either by coming into being out of formless matter, or by modification of an already existing form by a continued process of shaping. In the latter case the cause of this modification may lie either in the influence of a dissimilar male generative matter upon the female germ, or in the influence of other powers which operate only after procreation. In every living being there exists the capability of an endless variety of form-assumption; each possesses the power to adapt its organization to the changes of the outer world, and it is this power put into action by the change of the universe that has raised the simple zoophytes of the primitive world to continually higher stages of organization, and has introduced a countless variety of species into animate nature.”
By zoophytes, Treviranus here means organisms of the lowest order and of the simplest character, namely, those neutral primitive beings which stand midway between animals and plants, and on the whole correspond with our protista. “These zoophytes,” he remarks in another passage, “are the original forms out of which all the organisms of the higher classes have arisen by gradual development. We are further of opinion that every species, as well as every individual, has certain periods of growth, of bloom, and of decay, but that the decay of a species is degeneration, not dissolution, as in the case of the individual. From this it appears to us to follow that it was not the great catastrophes of the earth (as is generally supposed) which destroyed the animals of the primitive world, but that many survived them, and it is more probable that they have disappeared from existing nature, because the species to which they belonged have completed the circle of their existence, and have become changed into other kinds.”
When Treviranus, in this and other passages, points to degeneration as the most important cause of the transformation of the animal and vegetable species, he does not understand by it what is now commonly called degeneration. With him “degeneration” is exactly what we now call Adaptation or modification, by the action of external formative forces. That Treviranus explained this trans-transformation of organic species by Adaptation, and its preservation by Inheritance, and thus the whole variety of organic forms by the interaction of Adaptation and Inheritance, is clear also from several other passages. How profoundly he grasped the mutual dependence of all living creatures on one another, and in general the universal connection between cause and effect—that is, the monistic causal connection between all members and parts of the universe—is further shown, among others, by the following remarks in his Biology:—“The living individual is dependent upon the species, the species upon the fauna, the fauna upon the whole of animate nature, and the latter upon the organism of the earth. The individual possesses indeed a peculiar life, and so far forms its own world. But just because its life is limited it constitutes at the same time an organ in the general organism. Every living body exists in consequence of the universe, but the universe, on the other hand, exists in consequence of it.”
It is self-evident that so profound and clear a thinker as Treviranus, in accordance with this grand mechanical conception of the universe, could not admit for man a privileged and exceptional position in nature, but assumed his gradual development from lower animal forms. And it is equally self-evident, on the other hand, that he did not admit a chasm between organic and inorganic nature, but maintained the absolute unity of the organization of the whole universe. This is specially attested by the following sentence:—“Every inquiry into the influence of the whole of nature on the living world must start from the principle, that all living forms are products of physical influences, which are acting even now, and are changed only in degree, or in their direction.” Hereby, as Treviranus himself says, “The fundamental problem of biology is solved,” and we add, solved in a purely mechanical or monistic sense.
Neither Treviranus nor Goethe is commonly considered the most eminent of the German nature-philosophers, but Lorenz Oken, who, in establishing the vertebral theory of the skull, came forward as a rival to Goethe, and did not entertain a very kindly feeling towards him. Although they lived for some time in the same neighbourhood, yet the natures of these two men were so very different, that they could not well be drawn towards each other. Oken’s “Manual of the Philosophy of Nature,” which may be designated as the most important production of the nature-philosophy school then existing in Germany, appeared in 1809, the same year in which Lamarck’s fundamental work, the “Philosophie Zoologique,” was published. As early as 1802, Oken had published an “Outline of the Philosophy of Nature.” As we have already intimated, in Oken’s as in Goethe’s works, a number of valuable and profound thoughts are hidden among a mass of erroneous, very eccentric, and fantastic conceptions. Some of these ideas have only quite recently and gradually become recognized in science, many years after they were first expressed. I shall here quote only two thoughts, which are almost prophetic, and which at the same time stand in the closest relation to the theory of development.
One of the most important of Oken’s theories, which was formerly very much decried, and was most strongly combatted, especially by the so-called “exact experimentalists,” is the idea that the phenomena of life in all organisms proceed from a common chemical substance, so to say, from a general simple vital-substance, which he designated by the name Urschleim, or original slime. By it he meant, as the name indicates, a mucilaginous substance, an albuminous combination, which exists in a semi-fluid condition of aggregation, and possesses the power, by adaptation to different conditions of existence in the outer world and by interaction with its material, of producing the most various forms. Now, we need only change the expression “original slime” (Urschleim) into Protoplasm, or cell-substance, in order to arrive at one of the grandest results which we owe to microscopic investigations during the last ten years, more especially to those of Max Schultze. By these investigations it has been shown that in all living bodies, without exception, there exists a certain quantity of mucilaginous albuminous matter, in a semi-fluid condition; and that this nitrogen-holding carbon-compound is exclusively the original seat and agent of all the phenomena of life, and of all production of organic forms. All other substances which appear in the organism, besides these, are either formed by this active matter of life, or have been introduced from without. The organic egg, the original cell out of which every animal and plant is first developed, consists essentially only of one round little lump of such albuminous matter. Even the yolk of an egg is nothing but albumen, mixed with granules of fat. Oken was therefore right when, more divining than knowing, he made the assertion—“Every organic thing has arisen out of slime, and is nothing but slime in different forms. This primitive slime originated in the sea, from inorganic matter in the course of planetary-evolution.”
Another equally grand idea of the same philosopher is closely connected with his theory of primitive slime, which coincides with the extremely important Protoplasm theory. For Oken, as early as 1809, asserted that the primitive slime produced in the sea by spontaneous generation, at once assumed the form of microscopically small bladders, which he called “Mile,” or “Infusoria.” “Organic nature has for its basis an infinity of such vesicles.” These little bladders arise from original semi-fluid globules of the primitive slime, by the fact of their periphery becoming condensed. The simplest organism, as well as every animal and every plant of higher kind, is nothing else than “an accumulation (synthesis) of such infusorial bladders, which by various combinations assume various forms, and thus develop into higher organisms.” Here again we need only translate the expression little bladder, or infusorium, by the word cell, and we arrive at the Cell theory, one of the grandest biological theories of our century. Schleiden and Schwann, about thirty years ago, were the first to furnish experiential proof that all organisms are either simple cells, or accumulations (syntheses) of such cells, and the more recent protoplasm theory has shown that protoplasm (the original slime) is the most essential (and sometimes the only) constituent part of the genuine cell. The properties which Oken ascribes to his Infusoria are exactly the properties of cells, the properties of elementary beings, by whose accumulation, combination, and varying development, the higher organisms are formed.
These two extremely fruitful thoughts of Oken, on account of the absurd form in which he expressed them, were at first little heeded, or entirely misunderstood, and it was reserved for a much later era to establish them by actual observation. The supposition that the individual species of plants and animals originated from common prototypes by a slow and gradual development of the higher organisms out of lower ones, was of course most closely connected with these ideas. Man’s descent from lower organisms was likewise asserted by Oken—“Man has been developed, not created.” Although many arbitrary perversities and extravagant fancies may be found in Oken’s philosophy of nature, they must not prevent us paying our just admiration to these grand ideas, which were so far in advance of their age. This much is clearly evident from the statements of Goethe and Oken which we have quoted, and from the views of Lamarck and Geoffroy which have to be discussed next, that during the first decade of our century no doctrine approached so nearly to the natural Theory of Descent, newly established by Darwin, as the much decried “Natur-philosophie.”