The speech at the Scientific Congress in 1863 was the first open confession that Haeckel felt bound to make. But the real work for the new ideas began on his return to Jena. Nothing was further from Haeckel’s thoughts at that time than the idea of becoming merely the populariser of Darwinism in Germany. He has often been spoken of since in lay circles as such. It is entirely wrong. He had the courage to recognise his debt whenever he contracted one; and certainly Darwin supplied the groundwork of his colour-scheme. But he was much too independent and individual in his nature not to take the axe in his own hand at once and begin to hew away himself.
Darwin had strengthened his book with a large amount of the best material that zoology and botany could supply. But there was something else to be done: a theoretical treatment of a general character with cleverly grouped illustrations from the facts already provided by two sciences, and to reconstruct these sciences from their foundations on the basis of the new theory. At that time Haeckel was doing an incredible amount of work, with body and mind. He had an iron constitution. In the year of the Stettin speech he won a laurel crown at the Leipsic athletic festival for the long jump, with a leap of twenty feet. His physical strength seemed so inexhaustible that his host, Engelmann, put a pair of heavy iron dumb-bells in his bed, in case he should want to take exercise during the night. He had a proportionate strength of mind. Everything seemed to promise very well for the next few years, so that he could devote his whole health and strength to the great task of his life. His teaching did not give him very much trouble in a small university like Jena, that was only just beginning to have a scientific name. The happiness of his home life, with a highly gifted woman who shared all his ideas with the freshness of youth, began to chain the restless wanderer with pleasant bonds to his place. He, of course, expected to have his sea-holiday in the old way for the study of his little marine treasures, but otherwise he remained quietly in the valley of the Saale. The warmth of genial and most stimulating friendships gathered about his life. With his comfortable material position he set to work on his great task under the best auspices.
He would have had at the start material enough to work upon without Darwin. From Müller’s time he still had another special class of material, similar to the radiolaria, the medusæ.
The ship cuts through the ocean. It rises like a lofty fortress from the illimitable blue plain, with the white clouds on the far horizon. No land has been in sight for days. Yesterday a poor wind-borne butterfly rested on the deck. To-day it is gone, and all is sea. Then they suddenly appear silently in the blue mirror: mysterious discs, red as the anemones on a Roman meadow in spring, golden as the autumn leaves on a dark pond in the park, then blue, like a lighter blue floating on the general azure. They are the medusæ. At one time the ship sails through a whole swarm of them—thousands, hundreds of thousands, millions, a veritable milky way of coloured stars. On the next day they have all gone. No inhabitant of the ocean seems to be so close to it as this creature. The whole animal is only a shade more substantial than the water. You take it out, and try to catch hold of it. It stings your hand like a nettle: that is its one weapon. But it is already destroyed, melted away, a formless nothing. You put it on a piece of blotting-paper, and it dries up into the spectral outline of a shadow, a tiny “fat-spot,” summary of its whole existence.
Yet this soap-bubble of the water is a real animal. Its transparent body is shaped like a bell, and moves through the water by regular contraction and expansion, like the lung in breathing. Where the clapper of the bell should be, we find a stomach, with a mouth for eating, hanging down from the curved upper part. At the edge of the curved surface are many long fibrils that close on the approaching prey and paralyse it by their sting. Then it thrusts it into its mouth and swallows the object into the stomach. The medusa is, of course, a very lowly creature, but it is much more advanced in organisation than the tiny radiolarian. The radiolarian consists of a single cell. The medusa is a cell-state, a community of countless cells with a division of labour amongst them. Some of the cells form the wall of the bell, some the stinging threads, some the devouring and digesting stomach. In this the medusa comes nearer to man than the radiolarian. Some of the cells see to the reproduction of the medusa. Ova and spermatozoa are detached from the cell-community of the medusa’s body, blend together, and thus form the germ of a new medusa. In most cases the process is curious enough. From the germ-cell we get at first, not a real medusa, but a polyp that attaches itself to the ground, a little creature that may be remotely compared to the pretty water-lilies that meet the eye in an aquarium. Then the polyp produces something like a plant that grows buds, the real medusæ; it may produce these out of its substance as buds, and they then float away like detached flowers, or (in other species) it may gradually change itself into a chain of medusæ, of which the uppermost is detached first, then the next, and so on.
Since this peculiar method of reproduction became known, in the thirties or forties, the medusæ were regarded as amongst the most interesting objects in the whole of zoology. They offered an extremely difficult task to the investigator who would care to take up the study of them.
When Haeckel was with Johannes Müller in Heligoland in 1854 he made acquaintance with them for the first time. His artistic eye was caught with their beauty, as it was afterwards with the radiolaria. “Never shall I forget,” he says, “the delight with which, as a student of twenty years I gazed on the first Tiara and Irene [species of medusæ], and the first Chrysaora and Cyanea, and endeavoured to reproduce their beautiful forms and colours.” His predilection for the medusæ never disappeared. At Nice in 1856 he met them again in the Mediterranean. Gegenbaur’s Sketch of a Classification of the Medusæ provided his studies with a starting-point, just as Müller’s writings did afterwards for the radiolaria. At Naples and Messina he completed his mastery of them. When he had done with the radiolaria for the time after publishing the great monograph of 1862, the next task that loomed up on his horizon was the need for a “monograph on the medusæ.” It would be a long time, however, before he could complete the work in any fulness. A work of Agassiz that purported to do it, but, in his opinion, only confused the subject—he disliked both the Agassizs, father and son, and the father became one of his bitterest opponents on the Darwinian question—gave him a negative impulse to the study. He thought it would be best to deal with one family of the medusæ after another in separate monographs, as time permitted. The first of these essays appeared in 1864 and 1865, and dealt with what are known as the “snouted-medusæ” (geryonidæ). The first volume of the complete work was not published until fourteen years afterwards. If Haeckel had decided to work as a specialist he would have had material enough here to occupy him fully throughout the whole of the sixties, and even longer. The keen student of the radiolaria would be succeeded by the equally keen student of the medusæ. More folio volumes would have accumulated, with beautiful plates, such as only the technical student of zoology ever takes out of the library. His name, like that of his friend Gegenbaur almost, would never have reached the crowd.
It was the influence of Darwin that prevented this. His attention was turned in another direction, and we begin to realise the full greatness of his power when we remember that he nevertheless continued with unfailing quality to publish such detailed studies as those on the medusæ.
Darwinian ideas were fermenting intensely in his mind at that time. The most audacious practical and theoretical problems arose from the fundamental theory, and forced themselves on him at every moment. A great deal was sketched in outline in the Stettin speech, but the serious scientific work would have to be begun on his return to Jena, in his view. First, he thought, two features of Darwin’s system must be given a completely new and original complexion. Firstly, the bottom of the tree, where life begins. Secondly, the crown of all terrestrial evolution: the manner in which man is connected with the tree. It was his philosophic vein that settled both points, the philosophy of unity that sought to replace God by natural development, both below and above, in regard to the primitive cell and in regard to man. But the way in which he set about it was very far removed from all conventional philosophy. The whole rigour of his professional zoology found expression in it. And that was really the novelty of it. The same conclusions might have been drawn by any dozen ordinary philosophers, once they got on the right track. Even they could see that, if two and two are four, one and one are two, and three times three nine. Haeckel went very differently, and much more profoundly, to work.
