Haeckel

It was botany itself that thwarted all these designs. The examination had passed off happily. Rooms were taken at Jena, at the Easter of 1852, for the advanced study under Schleiden. Then the indefatigable collector had an adventure on a cold March day. He spent hours in the wet meadows by the river Saale, searching for a rare plant, the squill (Scilla bifolia). He met with the fate of the angler in the story, who fell into the water in his haste to secure his big pike. He landed the fish, but not himself. The plant was found, but Haeckel’s zeal was punished with a severe rheumatism. He had to go home to his parents at Berlin to be tended. At Berlin he begins his studies, and the event to some extent decides his career. It would now be many years before he would see Jena again; and through his efforts it would become one of the leading schools, not of botany, but of zoology—a school of philosophical zoology, however, in the sense of Schleiden.

Berlin had secured a botanist of the first rank a year before, Alexander Braun. He, too, was a thoughtful botanist, who would in his way agree very well with Schleiden. He was convinced that botany did not wholly consist in the determination of new plant forms and the almost fruitless effort to set up a system on which all particular diagnoses would be rigidly played as on a piano. He believed that there must be a more profound conception of it, which would take “form,” as such, as one of its problems, and would aim, not at the formation of as large a collection as possible, but at the construction of a science for which Goethe had long ago found a name—morphology, or the science of forms. It happened that Braun was a friendly visitor at the house of Haeckel’s parents at Berlin. The now convalescent freshman became devoted to him, body and soul; they became close friends, not merely master and pupil. Berlin at that time afforded many an opportunity for practical botanising. Rare marsh-plants then flourished in the bed of the Spree, which has since been cleared. The Botanical Garden was full of good things. Haeckel used to tell with pride, long afterwards, with what readiness he flung himself into the work, practical as well as theoretical, on these excursions with Professor Braun. “On one of our botanical expeditions we wanted to get a floating chara from a pond. Braun took off his boots in his usual way in order to wade to the spot. But I was before him. I quickly undressed, forgot my naughty rheumatism, and swam to the spot, to bring him a quantity of the plant he wanted. That was my first piece of heroism, perhaps my greatest.”

But in all this pleasant botanising there was no serious outlook on his future profession. Haeckel’s father, with his official way of looking at things, could not reconcile himself to scientific research as an avocation. It is an old belief that the way to all preoccupation with the science of living things lies through medicine. One may question that to-day. It was the rock on which Darwin nearly came to grief. A man may be a very gifted botanist, yet be quite unfitted for the medical profession. One must have a real vocation to become a physician, more than for any other calling, or else it is a hopeless blunder. The talents are divided in much the same way as between the historian and the soldier. It is true that the two may be united, but it is equally true that very good historians have made very poor soldiers. What the medical man learns in his studies is, of course, always valuable. But it offers no test of personal talent for scientific research, nor should it be supposed that a capacity of this kind would be able, by mere formal study, to acquire the true qualities of a physician. We must learn to appreciate the physician’s calling too much ever to look on it as an incidental occupation. It always reminds me of the amiable notion of the Philistine, that a man with a turn for poetry must first take up some solid profession, and then, once he is “in the saddle,” pour out verses in his leisure hours. Poetry can never be a mistress: it demands marriage or nothing. Otherwise—well, we have instances enough.

Haeckel himself afterwards said that he only acceded to his father’s wish, that he should study medicine, with a botanical mental reservation. He thought of going through the discipline conscientiously until he became a physician, and then secure a place as ship’s doctor, and travel over the world and see the tropics. Things turned out very differently. He never became a medical man such as his father had wished, but he passed over the profession into zoology. Botany remained the lost and never-forgotten love of his youth. When we look back on his whole career we can see that he was, on the whole, fortunate. Zoology afforded a richer, more abundant, and more varied material at that time. It proved to be more “philosophical.” He went after his father’s asses and found a kingdom. But to him personally it seemed to be an unmistakable renunciation—the first in an active career that was to see many resignations.

“He goes farthest who does not know where he is going.”

Haeckel once applied this motto to himself and his star, in a humorous after-dinner speech. With this kind of safe predestination he reached Würtzburg in the autumn of 1852 as a medical student. Medicine had in those days received an entirely new theoretical basis from Würtzburg—a basis that was calculated to attract a young inquirer, who brought much more of the general Faust-spirit to his work than aspiration to the profession and the doctor’s cap, or the practical side.

Let us recall for a moment how medicine had gradually reached the position of an independent science. Medicine was the outcome of a remote mythical epoch. It was content with the effect of certain venerable traditional medicaments on the living body, but knew little or nothing of the inner structure of the body on which it tried its drugs. The dissection and examination of even a corpse was regarded as a deadly sin, and was visited with secular punishment. Scientific medicine did not exist until this prohibition was removed; its first and most necessary foundation was anatomy, the science of the bodily structure and its organs. The art of “cutting up” bodies had seemed too revolting. Moreover, no sooner had the science of anatomy been founded than the range of the human eye itself was considerably enlarged. The microscope was invented. A new world came to light in the dissection of the body. Beyond their external appearance it revealed the internal composition of the various organs. The eye sees a shred of skin, a piece of intestine, or a section of the liver. The microscope fastens on a tiny particle of this portion of the body, and reveals in it a deeper layer of unsuspected structures. It is well known in the history of microscopic discovery that the more powerful lenses and the improved methods of research were only gradually introduced, and enabled students to found a new and much profounder anatomy. As soon as this science appeared it was given the special name of “histology,” or the science of the tissues (hista). Its particular achievement is the discovery that in man, the animal, and the plant, all the parts of the body prove, when sufficiently magnified, to be composed of small living elements, which are known as cells. The discovery of the cell was made in the latter part of the third decade of the nineteenth century. These cells join together in homogeneous groups in order to accomplish one or other function in the body, and thus form its “tissues.” Their intricate structure is unravelled by the histologist, microscope in hand. It is evident that in this way a new basis was provided for anatomy, and therefore also for medicine. In the fifties Würtzburg was the leading school of histology, or the science of these tissues composed of cells. Albert Kölliker, professor of anatomy there since 1847, published his splendid Manual of Histology at the very time when Haeckel was studying under him. Franz Leydig, a tutor there since 1849, was working in the same direction. The third member of the group, made professor in 1849, was Rudolf Virchow, a young teacher then in his best years. It was Virchow who did most to bring practical medicine into line with histology. As the vital processes in the human body seemed to him, with his strict histological outlook, to be traced back always to the tissue-building cells, he concluded that disease also, or the pathological condition of the body, and therefore the proper field of the medical man, was a process in these cells. Man seemed to him to be a “cell-state”: the tissues were the various active social strata in this state: and disease was, in its ultimate source, a conflict in the state between the citizens, the tissue-forming cells, that normally divide the work amongst them for the common good. Pathology must be cellular pathology. The science was already being taught by Virchow at Würtzburg, and the dry bones of it were covered with flesh for his hearers. But his ideas were not published until a few years afterwards (1858).

In the first three terms Haeckel studied chiefly under Kölliker and Leydig. They taught him animal and human embryology, as it was then conceived. Embryology was the science of the development of the individual animal or man, the description of the series of changes that the chick passes through in the egg or the human embryo in the womb. This science, also, had been profoundly affected by the invention of the microscope. Firstly, the spermatozoa, the active, microscopically small particles in the animal and human sperm, had been discovered. Then, in the twenties, Karl Ernst von Baer had discovered the human ovum. The relation of these things to the cell-theory was clear. It was indubitable that each of these male spermatozoa and each female ovum was a cell. They melted together and were blended into a new cell in the act of procreation, and from this, by a process of repeated cleavage of cells, the new individual was developed with all his millions of cells and all the elaborate tissues that these cells united to form. A whole world of marvellous features came to light, but the key to the unriddling of them was still wanting.

However, the Würtzburg school was at least agreed as to method, which was the main thing; its leaders were determined to press on to the solution of these problems on purely scientific lines. Everything was to be brought into a logical relation of cause and effect, and there was to be no intrusion of the supernatural, no mysticism. Natural laws must be traced in the life of the cells and in the history of the ovum and the embryo. The cells were to be regarded in the same way as the astronomer regards his myriads of glittering bodies. In this way the science of histology had been founded, and embryology had assumed a scientific character in the hands of Von Baer. The microscope kept the attention of students to facts, and did not suffer them to lose themselves in the clouds. Thus a foundation-stone was laid in Haeckel’s thoughts which he would never discard.

In the later years of the Darwinian controversy he was destined to come into sharp conflict with both Virchow and Kölliker. Each of them came to look on him as the sober hen does on the naughty chick it has brought into the world, that madly tries to swim on the treacherous waters of Darwinism. But forty years afterwards—after many a knife-edged word had been thrown in the struggle—the aged Kölliker was one of those who entered their names in the list of men of science who erected a bust in the Zoological Institute at Jena in honour of Haeckel’s sixtieth birthday.

However, it was a different, an apparently trivial, yet, as it turned out, most momentous interest that quickened him during these University years.

The impulse to microscopic research, that had led to the foundation of histology and embryology, had brought about a third great advance which had an important bearing on zoology. When we stroll along the beautiful shore of the Mediterranean at Naples to-day, with eyes bent on the blue surface from which Capri rises like a siren, and on the cloud-capped Vesuvius with its violet streaks of lava cutting across the green country, we notice in the foreground of the picture a stout building, with very large windows, planted with the boldness of a parvenu amongst the foliage. It is the “Zoological Station,” built by Dohrn, a German zoologist, at the beginning of the seventies. Anton Dohrn was one of Haeckel’s first pupils, and was personally initiated by him into the study of marine life, at Heligoland in 1865. Zoologists who work in the station to-day find it very comfortable. Little steamers with dipping apparatus bring the inhabitants of the bay to them. There is a large aquarium at hand. You sit down to your microscope, and work. The material is “fresh to hand” every day. There are now many of these stations at well-exposed spots on the coast in various countries—sea-observatories, as it were, in which the student examines his marine objects much as the astronomer observes his planets and comets and double stars at night. To-day, when a young man is taking up zoology, and he is asked what university he is going to, he may say that he is going down to the coast, to Naples, to do practical work. When the long vacation comes, swarms of professors go from the inland towns to one or other seaside place, as far as the purse will take them. All this is a new thing under the sun. The zoologist of the olden days sat in his study at home. He caught and studied whatever was found in his own district. The rest came by post—skins, skeletons, amphibians and fishes in spirit, dried insects, hard shells of crustacea, mussels and snails of all sorts; but only the shells always, the hard, dry parts of star-fishes, sea-urchins, corals, &c. Animals of the rarest character were thrown away because they could not very well be preserved in spirit and sent from the North Sea or the Mediterranean to Professor Dry-as-dust. In this state of things the advance in microscopic work brought no advantage. But at last it dawned on students that the sea is the cradle of the animal world. Whole stems of animals flourished there, and there only. Every wave was full of innumerable microscopic creatures, of the most instructive forms. Amongst them were found the young embryonic forms of familiar animals. At last the cry, “To the sea,” was raised. The older professor of zoology had suffered from a kind of hydrophobia. It was not possible to teach very much at Berlin about the anatomy, histology, and embryology of the sea-urchin from a few dried flinty shells. At Würtzburg, animals were subtly discussed by men who had never made a journey to see them, while they were trampled under foot every day by the visitors bathing in Heligoland. They must move. It was not necessary to go round the world: a holiday journey to the North Sea or the Mediterranean would suffice. Every cultured man had always considered that he must make at least one pilgrimage to classic lands before his education was complete. It was only a question of changing material. They were not to confine themselves to examining ruined temples and aqueducts, but to take their microscopes down to the coast, draw a bucketful of sea-water, and examine its living contents—the living medusa and sea-urchin, and the living world of the swarming infusoria. But it was like the rending of the great curtain of the temple. Zoology seemed to expand ten-fold, a hundred-fold, in a moment. A room in an obscure inn by the sea, a microscope, and a couple of glasses of salt-water with sediment every morning—and the finest studies at Paris and London were as ploughed land, without a single blade, in face of this revelation. It was a Noah’s ark in the space of a pinch of snuff.

One day the young medical student heard, in the middle of his histology and zoology, that Kölliker had come back from Messina. He had been studying lower marine life there. In 1853, two young men were together in the Gutenberg forest near Würtzburg. One of them, Karl Gegenbaur, had been abroad with Kölliker. With his impressions still fresh, he tells Haeckel about his zoological adventures in the land of the Cyclops.

Gegenbaur, eight years older than Haeckel, was by birth and education a typical Würtzburger. He, too, had studied medicine, and had practised at the hospital. But he had already advanced beyond that. His stay at Messina had been devoted entirely to zoological purposes. A year later he would be teaching anatomy at Würtzburg, and a year later still he would be called to Jena. From that time he began to be known as a master of comparative anatomy—especially after 1859, when his Elements of the science was published, a classic in its way that still exercises some influence.

There is nothing romantic in his career, nor could we seek any element of the kind in a man of Gegenbaur’s character. But his young and undecided companion seemed to catch sight of a new ideal as he spoke. He would complete his medical studies, and then shake himself free of surgery and hospital. He would take his microscope down South, where the snowy summit of Etna towered above the orange-trees, and study the beautiful marine animals by the azure sea and the white houses, in the orange-laden air, and drink in ideas at the magic fount of these wonderful animal forms, and live out the lusty, golden years of youth on the finest coast in Europe. From that moment Haeckel felt a restless inspiration. He had no idea what it was that he was going to investigate at Messina; and he certainly did not know when and how he was to get there. But he continued his medical studies with a vague hope that it was only preliminary work; that some day he would do what his friend Gegenbaur had done.

They were very good friends, these two. They were drawn together by the strong magnetism of two true natures that understood each other to the golden core, though in other respects they were as different as possible. Gegenbaur was no enthusiast. His ideal was “to keep cool to the very heart.” But he was at one with Haeckel in a feeling for a broad outlook in scientific research. He never shrank from large connections or vast deductions, as long as they were led up to by a sober and patient logic. This logical character he afterwards recognised in Darwin’s idea of evolution, and so the friends once more found themselves in agreement, and for a long time they were a pair of real Darwinian Dioscuri. This feeling for moderation and at the same time for far-reaching logic was combined in Gegenbaur with a certain steady and unerring independence of character. He made little noise, but he never swerved from his aim. What he accomplished with all these qualities, in many other provinces besides Darwinism, cannot be told here. It may be read in the history of zoology. He had, as far as such a thing was possible, a restful influence of the most useful character on Haeckel. If we imagine what Darwinism would have become in the nineteenth century in the hands of such men as Gegenbaur, without Haeckel, we can appreciate the difference in temperament between the two men. With Gegenbaur evolution was always a splendid new technical instrument that no layman must touch for fear of spoiling it. With Haeckel it became a devouring wave, that will one day, perhaps, give its name to the century. In other natures these differences might have led to open conflict. But Haeckel and Gegenbaur show us that, like so many of our supposed “differences,” they can at least live together in perfect accord in the freshest years of life, each bearing fruit in its kind.

When we find Haeckel intimate in this way with Gegenbaur, his senior by eight years, we realise how close he was at that time to the whole of the Würtzburg circle. The two generations were not yet sharply divided, as they subsequently were. Most of them fought either with or against him at a later date, but they belonged, at all events, to the same stratum. But the split between the two generations was felt when one pronounced the name of Johannes Müller, of Berlin—the physiologist (not the historian).

All who then taught histology, embryology, comparative anatomy, or cellular pathology at Würtzburg had sat at his feet, either spiritually or in person. Johannes Müller, born at the beginning of the century, was appointed Professor of Anatomy and Physiology at Berlin the year before Haeckel was born. That indicates the distance between them. It was in Müller’s incredibly primitive laboratory that, as Haeckel tells, the theory of the animal-cell was established by his assistant, Theodor Schwann, after Schleiden had proved the vegetal cell. Müller himself had founded histology in his own way. He was the real parent of the idea that the zoologist ought to go and work by the sea. We have a model of this kind of work and at the same time a superb work for embryological matters in Müller’s epoch-making Studies of the Larvæ and Metamorphoses of the Echinoderms. He had brought comparative anatomy beyond the stage of Cuvier, to a point where Gegenbaur could begin. From his school came Rudolf Virchow, who applied the cell-theory to medicine, and Emil du Bois-Reymond, who opened out a new path in physiology by his studies of animal electricity. Müller had done pioneer work with remarkable vigour in all the various branches of research, diverging afterwards to an enormous extent, that pursue these methods. The many-headed (young and half-young) generation, in which Haeckel was growing, saw the whole previous generation embodied in the single name of Müller. He seemed to be a kind of scientific Winkelried, except that the fifty spears he bore on his breast were so many lines of progress emanating from him alone.

Johannes Müller had the great and splendid gift of never lying on the shoulders of his pupils with an Alpine weight of authority. It was a secret of his personality that we admire but can hardly express in words to-day. Everybody learned from him what a great individuality is. He exerted a kind of moral suggestion in teaching men to be free, great, enlightened, and true. His pupils have worked at the development of his ideas with absolute freedom. No part of them was to be regarded as sacred, and, as a matter of fact, in the chief questions no part has remained.

One approaches the inner life of a man like Müller with a certain timidity, and asks how he became what he was. There can be no question that the fundamental trait of his character was a peculiarly deep religious feeling. At heart he was a mystic. The whole magic of his personal influence sprang from these depths. By profession he was a physiologist, an exact scientist. Never did he swerve a hair’s breadth from the iron laws of research. But beneath it all was a suppressed glow of fervour. Every one who understood him, every one who was a true pupil of his, learned it by a kind of hypnotism. Externally he was all for laborious investigation, whether in dissecting a star-fish for you or classifying fishes—though he would have a full sense of your ardent longing for an inner trust in life and a philosophy of life. Both elements might change considerably in the pupil: the method of investigation without—the ideal of the comprehensive vision within. But what never left any man who had followed Müller was the warning cry that these things, within and without, should go together; that, in the larger sense, it is not possible to count the joints in the stalk of an encrinite without feeling a thrill in the deepest depth of the mind and the heart.

It is so common a spectacle in history for disciples to condemn their masters with cold smiles that we forget how pitiful it is. No pupil of Johannes Müller has ever felt that he had done with him, and might quit him with ingratitude. He had pupils, it is true, who did not lack belief in themselves, and who became famous enough to give them a sense of power; men who have eventually come to conclusions diametrically opposed to those that Müller had taught them. Yet they respect him. Living witnesses still tell of the glance that bored into you, and could not be evaded. But there must have been a greater power in the man than this piercing glance. It was a glance that survived the grave, and laid on one a duty; a glance that shot up in the darkness of memory if the duty was not fulfilled—the duty of going to the foundation of things. Whether you are examining the larva of an echinoderm or the light of a distant star, God is there. Whether you explain your echinoderm-larva in this way or that; whether you believe your star to be a sun or a burnt-out cinder; whether you conceive God in this way or another—you shall feel that the bridge is there in absolutely everything. Every glance into the microscope is a service of God. It was Goethe’s deepest sun that threw a great, radiant spark out of this curious, dark, angular, unintelligible jewel.

Such a man was bound to be more than Kölliker, Virchow, and Gegenbaur to Haeckel. Müller was still teaching at Berlin, and Haeckel’s best star brought him to sit in reality at the feet of the great teacher, who could so well speak soul to soul to him.

At the Easter of 1854 Haeckel returned from Würtzburg to Berlin. He was now twenty years old, and it was at this juncture that, to use his own phrase, the vast impression of Müller fell on him. A portrait of Müller still hangs over the desk in his study in the Zoological Institute at Jena. “If I ever become tired at my work,” he says, “I have only to look at it to get new strength.” The influence of the much older man, who, however, died at a far earlier age than Haeckel will do, only lasted for a short time. But Haeckel has preserved a memory of him that is only eclipsed by the memory of one other man—Darwin. Müller did not live to read Darwin’s decisive work, so that these two great ideals of Haeckel’s never crossed each other, either for good or evil. He himself felt that there was a pure evolution from one to the other in his mind.

In the summer of 1854 he studied comparative anatomy under Müller, for which Kölliker had sufficiently prepared him. He has recorded his first impressions. “I soon got to know him personally, but I had so great a respect for him that I did not venture to approach him more closely. He gave me permission to work in the museum. I shall never forget the hours I spent there, drawing skulls, while he walked up and down, especially on Sunday afternoons. Often when he went past me I wanted to ask him something. I went up the step with beating heart and took hold of the bell, but returned without venturing to say anything.” Müller took some notice of the zealous young student. When the long vacation came round in August, and the master, following the new custom, packed up his bundle in order to spend two months on practical work by the sea, he allowed Haeckel to go with him. Müller’s son and the later Professor La Valette joined the party. They went to Heligoland. Müller taught his pupils his simple method of studying the living subject. There was no witchcraft in it, but it had had to be invented by some one. They put out to sea in a small boat. A little net of linen or fine gauze, with a wide opening and short body, was fastened on a pole. The mouth of the net was thrust directly under the surface or a little deeper, vertically to the surface, and the boat was slowly rowed forward. The contents of the filtered sea-water remained in the meshes of the net, and were from time to time emptied into a glass containing sea-water. “I shall never,” says Haeckel, “forget the astonishment with which I gazed for the first time on the swarm of transparent marine animals that Müller emptied out of his fine net into the glass vessel; the beautiful medley of graceful medusæ and iridescent ctenophores, arrow-like sagittæ and serpent-shaped tomopteris, the masses of copepods and schizopods, and the marine larvæ of worms and echinoderms.” Müller called these very fine and generally transparent creatures, of whose existence no one hitherto had had any idea, “pelagic sweepings” (from pelagos, the sea). More recently the word “plancton” (swimming matter) has been substituted for his phrase. As we now send whole expeditions over the seas to study “plancton,” the word has found its way into ordinary literature. The regular anglers who were then in Heligoland must have looked on this subtle work with a butterfly net as a sort of pleasant joke born from the professional brain. The young student must have made an impression on them with his vigour, though he had not yet turned himself into a marine mammal, living half in the water for days together. They called him a “sea-devil.” What pleased the master most in him was the talent he already showed of quickly sketching the tiny, perishable creature from the surface of the sea while it was fresh. Haeckel had been passionately fond of drawing from his early years. Now the old bent agreed with the new zeal for zoology. “You will be able to do a great deal,” Müller said to him. “And when once you are fairly interested in this fairy-land of the sea, you will find it difficult to get away from it.” The dream of Messina, that Gegenbaur had conjured up, seemed to draw nearer.

These lively days at Heligoland provided Haeckel with the material for his first little zoological essay. It dealt with the development of the ova of certain fishes (On the Ova of the Scomberesoces, published in Müller’s Archiv for 1855). Müller lent him ova from the Berlin collection to complete his study. It is the same volume of the Archiv in which, in Reichert’s introduction, the great controversy breaks out over Virchow’s pregnant assertion that each human being is a state composed of millions of individual cells.

Haeckel remained with Müller at Berlin for the whole winter, and was drawn more and more into the province of comparative anatomy, or, to speak more correctly, zoology. The official Professor of Zoology at Berlin at the time was really the aged Lichtenstein, who had occupied the chair since 1811. Haeckel has humorously described himself in later years as self-taught in his own subject, saying that he had attended many most excellent colleges, but never visited an official school of zoology. The only opportunity to do so at the time was under Lichtenstein, but that professor bored him so much that he could not attend his lectures. Lichtenstein was a venerable representative of the old type of zoologist; his ideal was to give a careful external description of the species on the strength of specimens chosen from a well-stocked museum. A whole world lay between these surviving followers of Linné and the splendid school of Johannes Müller.

However that may be, the fact was that under these alluring attractions Haeckel’s studies were drifting from the medical profession to an “impecunious art.” But as medical work had been chosen, if only as a temporary occupation, Haeckel had to tear himself away from the great magnet, at the Easter of 1855, by removing to a different place. He chose, as the least intolerable compromise, to return to Würtzburg. At all events we find him spending three terms there. I have already said that Rudolf Virchow was one of the distinguished Würtzburgers at the time who sought most keenly the solution of the new problems of biology on the medical side. Hence Virchow had to help him to find the bridge between the work he really loved and the work he was obliged to do. As a fact, Virchow directed the whole of his studies on this side in the three terms.

Virchow was not so fascinating as Johannes Müller, even in his best years. But it was something to be initiated into medical science by such a man. A later generation has, unfortunately, grown accustomed to see mental antipodes in Virchow and Haeckel. In 1877 they had a controversy with regard to the freedom of science that echoed through the whole world of thought. Yet seventeen years afterwards Haeckel himself (who was first attacked by Virchow), looking back on the days he spent at Würtzburg, had nothing but grateful recognition to say of Virchow. “I learned,” he says in 1894, “in the three terms I spent under Virchow the art of the finest analytic observation and the most rigorous control of what I observed. I was his assistant for some time, and my notes were especially praised by him. But what I chiefly admired in him at Würtzburg was his wide outlook, the breadth and philosophic character of his scientific ideas.”

The theory that Virchow put before his pupils was pure Monism, or a unified conception of the world without any distinction of physical and metaphysical. Life was defined, not as a mystic eccentricity in an orderly nature, but plainly as a higher form of the great cosmic mechanism. Man, the object of medical science, was said to be merely a higher vertebrate, subject to the same laws as the rest.

We can see very well that this was quite natural. If there was any man likely to put forward such views it was Virchow. He had passed through Müller’s school, but was now one of the younger group who, even during Müller’s life, were gradually adopting certain very profound views on life and man, without any particular resistance on the master’s part. The chief characteristic of nearly the whole of this group was the lack of the volcanic stratum below of deep and personal religious feeling; in Müller this had been throughout life an enchained Titan among the rocks of his logical sense of realities, yet it had given a gentle glow and movement to the floor of his mind. Rudolf Virchow was the coolest, boldest, and clearest-minded of the group. He went to the opposite extreme. If Müller was standing on a volcano, which he only repressed by the giant force of his will—a nature that was above all master of itself—Virchow, on the contrary, was standing on a glacier, and he had never taken the trouble to conceal it. I should not venture to count him amongst the instinctively Monistic minds, in the sense of Goethe, to whom the unity of God and nature, the inorganic and the organic, the animal and the man, comes as an ardent and irresistible feeling. But it would have been strange if, in those years and in the middle of the whole scientific current of his time, his own organ, his icy logic, had not led him to the same conclusion; that it is a simpler method of research to believe in natural law alone, to regard the living merely as a complex play of the same forces that we have in physics and chemistry, and to consider man, with the bodily frame of an ape-like mammal, to be really such an animal. I believe, indeed, that Virchow never abandoned this simple solution in his own mind at any part of his career. The controversy he afterwards engaged in ran on different lines. It seems to me that at an early stage of his development he became convinced that there must be limits to scientific inquiry, not on logical, but on diplomatic grounds; because it is not an absolute agency, but only a relatively small force amongst many more powerful institutions, the Church, the State, and so on. Hence it would have to respect limitations that were not drawn from its own nature; in given cases it would have to keep silent in order not to jeopardise its existence as a whole. It is my firm belief that this diplomatic attitude as such would lead to the destruction of all pursuit of the truth. It carefully excludes the possibility of any further martyrdoms, but at the cost of science’s own power to illumine the world. In my opinion the free investigation of the truth is an absolute right. Churches, States, social orders, moral precepts, and all that is connected with them, have to adjust themselves to this investigation, and not the reverse.

However, the point is that under Virchow—more particularly under Virchow, in fact—Haeckel would be educated into the general attitude with regard to God, nature, life, and man, to which he has since devoted his whole energy. In spite of Goethe—and who would be likely to take Goethe as his guide in his twenty-first year?—the ardent young student was as yet by no means firmly seated in the saddle. He grubbed, and sought, and rejected. In his Riddle of the Universe he tells us that he “defended the Christian belief in his twenty-first year in lively discussions” with his free-thinking comrades, ... “although the study of human anatomy and physiology, and the comparison of man’s frame with that of the other animals, had already greatly enfeebled my faith. I did not entirely abandon it, after bitter struggles, until my medical studies were completed, and I began to practise. I then came to understand Faust’s saying, ‘The whole sorrow of humanity oppresses me.’ I found no more of the infinite benevolence of a loving father in the hard school of life than I could see of ‘wise providence’ in the struggle for existence.”

When the three terms of medical training were over, he received another impulse to his own particular interest in science. Kölliker invited him in August, 1856, to spend the two months’ holiday with him on the Riviera. It was the first Mediterranean school of zoology, though as yet only a kind of “payment on account.” On the journey he made the acquaintance of the zoological museum at Turin and its well-travelled director, Filippo de Filippi, and he saw the grandeur of the Maritime Alps on the Col di Tenda. The master, Kölliker, Heinrich Müller, Karl Kupffer (afterwards professor at Munich), and he established themselves at Nice, and fished for all sorts of creatures with the Müller-net at Villefranche. Fortunately, Müller himself happened to be visiting the Riviera at the same time, and they received a direct stimulus from him. The first result of this journey in the summer and autumn was that Haeckel secured his degree with a zoological-anatomical work, instead of with a strictly medical treatise. As he had done from Heligoland two years before, he now brought home from the Mediterranean the material for a short technical theme. He again spent the winter at Berlin to put it together. It was an histological study of the tissues of crabs, and therefore lay in the province of the articulates, an animal group, it is curious to note, which he has not entered into more fully in the course of his long and varied work as special investigator. At Nice he made a thorough study of the nerve-tubes of the spiny lobster and other available marine crustacea, and discovered several remarkable new structural features in them. At Berlin he entered upon a minute microscopic study of the common craw-fish. His dissertation for the doctorate embodied the main results of his research. It was entitled De telis quibusdam Astaci fluviatilis, and was printed in March, 1857. It appeared the same year in an enlarged form in Müller’s Archiv, with the title The Tissues of the Craw-fish. On March 7th he received his medical degree, Ehrenberg, the great authority on the infusoria, presiding. In the customary way the young doctor had to announce and defend several theses. One of them is rather amusing in view of later events.

He most vigorously contested the possibility of “spontaneous generation.” The meaning of the phrase is that somewhere or at some time a living thing, animal or plant, has arisen, not in the form of a seed or germ or sprout from a parent living thing, but as a direct development out of dead, inorganic matter. Haeckel had not made a personal study of the subject. What he said in his thesis was merely a faithful repetition of Müller’s opinion. At that time it was believed that science had empirically disproved spontaneous generation. An old popular belief held that fleas and lice were born every day from non-living dirt and dust, but that had been refuted long before. No egg, no animal: every living thing develops from an egg. This had been laid down as a fixed rule. When the microscope revealed an endless number of tiny creatures in every drop of stagnant water, in the air and the dust and the soil, it was a question whether the rule was not wrong. Surely these simplest of all living things, apparently, were born by spontaneous generation? However, the question was believed to have been settled in two ways. Schwann, the co-discoverer of the cell-theory, had made certain experiments which seem to prove directly that even these tiny beings, the infusoria and bacteria, were never formed in a vessel containing water and dead matter, if it had been carefully assured beforehand that the minute living germs of these animals that floated in the air could not penetrate into the vessel. At the same time Ehrenberg and others stoutly denied that the infusoria were the “simplest” organisms, or that they could conceivably be born in that way. They declared that the infusoria were “perfect organisms” in spite of their smallness. The belief that these tiny creatures consisted of “one cell,” and so formed, as it were, the ultimate elements of the plant and animal worlds on the lines of the cell-theory, was seriously menaced, and apparently on the way to be destroyed. Finally, the tapeworm and similar parasites had been declared to evolve by a kind of spontaneous generation from the contents of the intestines. But this also was proved to be untrue. Thus there was ample material for a solid dogma: there was no such thing as spontaneous generation. The dogma, moreover, harmonised with the prevailing belief in a special vital force and a radical distinction between the living and the dead, which was still shared in a subtle form by even a man like Müller. The dogma was formulated. Spontaneous generation was struck out of the scientific vocabulary as unscientific and a popular superstition. The young doctor, duly initiated into these ideas of the time, could not resist the temptation to give his own kick to the fallen theory. Yet how strangely things have changed since then! Two years afterwards Haeckel ceased to believe in a special vital force; he was now absolutely convinced that there were unicellular beings; his whole theory of life seemed to demand spontaneous generation as a postulate, and he even doubted the force of the experiments of Schwann and others. Haeckel himself became the keenest apostle of the theory of spontaneous generation. Whenever it is mentioned to-day, we think of the weight of his name which he has cast in the scale in its favour. So the leaves change even in the forest of science: yesterday green, to-day red and falling, to-morrow green once more. On the same branch as the dogmas we find the correctives growing, that will at length split them open and cast them as empty husks to the ground.

The history of Haeckel’s medical doctorate can be written in a few plain and touching lines. After receiving his degree he was sent by his prudent father, to keep him away from crabs and other monsters of the deep, to Vienna for a term, to do hospital work under Oppolzer, Skoda, Hebra, and Siegmund. All that we find recorded of this term is that his old love of botany revived in earnest. Immense quantities of dwarf Alpine plants were collected. When the traveller passed by the spot twenty-four years afterwards on a quiet autumn Sunday, on his way to take ship at Trieste for the tropical forests and giant trees of Ceylon, the memory of Schneeberg and the Rose-Alp came upon him like a dream. However, the hospital work, together with a short span of cramming in the winter at Berlin, must have had some effect, as he passed the State-examination in medicine. In March, 1858, he was a “practising physician.” He had in his hand the crown of prudent ambition—and he felt like a poor captive. There was one source of consolation—Johannes Müller. While one was near him there was a possibility of more real work. He discussed with him the plan of the study of the development of the gregarinæ (parasitic protozoa), which he wanted to conduct in Müller’s laboratory in the summer of 1858. Then he was stricken, like so many others, with the thunderbolt of the news of Müller’s sudden death, on April 28th of the same year. What must he do now? He began to practise. It is said on his own authority that he fixed the hours of consultation from five to six in the morning! The result was that during a whole year of this philanthropic occupation he had only three patients, not one of whom died under his earnest attention.

“This success was enough for my dear father,” says Haeckel. We can well believe it.

The kindly old man consented to one more year of quite extravagant study, in which all was to come right. It was to be a year of travel, in Italy. He was to devote himself to the study of marine animals, not merely for pleasure, but earnestly enough for him to find a basis for his life in the result. This he succeeded in doing. Like the children of fortune, who at the very moment when they cannot see a step before them make a move that the Philistine regards as the safest and last refuge, Haeckel becomes engaged that very year to his cousin, Anna Sethe. After that, in January, 1859, he goes down to the coast. He makes for the blue Mediterranean, which he already knows will prove anything but an “unprofitable sea” for him. He will conjure up treasures of science from its crystal depths with his Müller-net; then on to fortune, position, marriage, and the future. The fates have added a world-wide repute, if they have denied many a comfort.