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.
Fishing in Heligoland in 1865.
Anton Dohrn (Naples). Richard Greeff (Marburg). Ernst Haeckel (Jena).
Max Salverda (Utrecht). Pietro Marchi (Florence).
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.