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.