It is very instructive to note how Virchow shifted his position a little in accordance with the time. In his judgment science had to make peace. It had to make concessions in certain directions. In 1863 he had spoken of the “ruling Churches.” Now, in 1877, he speaks of the freedom of science in the “modern State.” The great Kulturkampf had set in. The Church was for the time being powerless in face of the State. Hence Virchow now plays off the State as the guardian of his tabooed province. This time Darwinism is supposed to be threatening the virgin field in which we exact scientists make our peace with the State. At the right moment he adroitly points out that the Social Democrats have taken to Darwinism. Every man on deck, then. That must not go any further. At the bottom it was the old contest. If one lays down as a general principle that the scientific pursuit and presentment of truth has to respect neutral provinces and make concessions, every change in current affairs will demand a fresh application of it. To-day it is some Church or other, to-morrow a State, the next day the momentary code of morals, and lastly some bumbledom or other that renews the prohibition to dissect corpses, because our dissecting knives disturb the peace of mind of our Philistine neighbours. Haeckel published a sharp reply to Virchow (Free Science and Free Teaching, 1878), in which he sought to show amongst other things, taking his stand on his political principles, that Socialism and Darwinism have nothing to do with each other.
I will not go more fully into the controversy here. If one province of knowledge is to receive light from another at all, we must admit that there is only one general truth. All stationary or reactionary political interest is irreconcilable with the theory of evolution. That is clear from the very meaning of the words. As to the direction in which we must seek real political and social progress opinions are bound to differ very considerably; it may be shown that the laws of evolution which have selected the various species of plants and animals can only be used very sparingly and cautiously for the promotion of human progress. But I believe that is quite an immaterial point in this matter of Virchow’s attack. The real influence of Darwinism on political questions is not the chief question. The principle we have to determine is whether the freedom of scientific research and the teaching of what the individual student believes he has discovered to be true are to have “external” restrictions or not. The question is whether inquiry and teaching are to be regarded merely as things “tolerated” and interfered with at will amongst the various elements of modern life; or whether they are not to be considered the very bed-rock of civilisation, and every agency that has power for the moment is not doomed whenever it comes into collision with them.
In this momentous duel of the two men who were regarded at the time as unquestionably the most distinguished scientists in Germany it seemed to most people for a time that Haeckel had gone off altogether into general and public questions with regard to the aim of research and philosophy. He seemed to lend colour to the belief as he published, in quick succession, a number of new popular lectures (Cell-souls and Soul-cells, 1878, and The Origin and Evolution of the Sense-organs, 1878), and at the same time published a collected volume of older and recent Essays on the Theory of Evolution (one part in 1878, a second in 1879, and a new and enlarged edition in 1902). As a matter of fact, we find him in these years occupied with a small but particularly well-lit field of his whole work. It was not merely that in a few years he buried himself in the primitive forests of Ceylon, in order to pursue his special studies far removed from all civilisation for months together. Just at this date appeared the great monograph on the medusæ, which he had at length concluded. The first volume (The System of the Medusæ, with 40 coloured plates) was published in 1879, and the second (The Deep-sea Medusæ of the Challenger Expedition and the Organisms of the Medusæ, with 32 plates) in 1881. And while these splendid volumes showed his academic colleagues that he had no mind to remain entirely on the outer battlements as a philosophic champion, he plunged up to the ears in a new special study of a range that would have made even the most enthusiastic specialist recoil.
From December, 1872, to May, 1876, the English had conducted a peaceful enterprise that will be for ever memorable. A staff of distinguished naturalists had gone on the ship Challenger to explore the depth, temperature, and bottom of remote seas. With the aid of the best appliances specimens of the mud from the floor of the ocean (sometimes more than a mile in depth) were brought up at 354 different spots. It was known from earlier deep-sea explorations that this slime on the floor of the ocean, from a certain coast-limit into the deepest parts, is composed for the most part of the microscopically small shells of little marine animals. The living creatures that form these shells swim in the water of the ocean, partly at the surface and partly at various depths beneath it. When they die the little hard coat of mail sinks to the bottom, and as there are millions upon millions of them living in the sea, thick deposits are gradually formed at the bottom that consist almost entirely of these microscopic shells. The animals in question are primitive little creatures consisting of a single cell, of the type that Haeckel has called “Protists.” Even in Ehrenberg’s time it had been noticed that amongst the shells in the deep-sea mud there were, besides chalky shells, a number of graceful flinty coats that clearly pointed to the radiolaria. The Challenger expedition now made the great discovery that vast fields at the floor of the ocean, especially of the Pacific, were covered almost exclusively with these flinty shells. It was seen at once that the few hundred species of radiolaria that had hitherto been described by Haeckel and others were only a very small part of the masses of radiolaria found in the ocean. The specimens of the deposits which were carefully preserved and brought home by the Challenger contained such an immense number of unknown species with their flinty shells faultlessly preserved, that it was necessary to reconstruct the whole of this wonderful group of animals. And who could be better qualified for the work than the man who had already made a name by his study of the radiolaria, Haeckel?
When the English Government came to publish the results of the Challenger expedition in a monumental work (of fifty volumes), he was entrusted with the work on the siphonophores, the corneous sponges, and all the radiolaria in the collection. For ten years, from 1877 to 1887, Haeckel devoted every available hour to the work of selecting the radiolarian shells with his microscope from these specimens of the deep-sea deposits, and naming, describing, and drawing the new species. When he began his task 810 species of radiolaria were known to science. When he came to his provisional conclusion, ten years afterwards, though his material was not yet exhausted, there were 4,318 species and 739 genera. They are described in the splendid work that he wrote for the Challenger Report. It consists of two volumes of text (in English) with 2,750 pages and 140 large plates, with the title, Report on the Radiolaria collected by H.M.S. Challenger. In the preparation of these plates (and in the illustration of all his later works) he had the very valuable assistance of the gifted Jena designer and lithographer, Adolph Giltch. A good deal of new information with regard to the living body of the radiolaria had come to light since 1862. In particular it had now been settled beyond question that they consisted merely of a single cell. There was, therefore, a good opportunity of reconstructing the Monograph of 1862 with the new and more comprehensive work. The chief contents of the English work (with a selection of the plates) were then published in German, and appeared in 1887 and 1888 as the second, third, and fourth parts of the Monograph on the Radiolaria. A sort of supplementary essay on the methods of studying the radiolaria and cognate “plancton” animals was published separately with the title of Planctonic studies (1890). Though it was a moderate and tactful criticism of the methods of some of his colleagues in this kind of work, it was “refuted” by them in a way that it would be difficult to qualify—in other words, it was fruitlessly assailed with charges of the most general but most unpleasant character. In the English Report we find two other volumes afterwards from Haeckel—the volume on the siphonophoræ in 1888, and the Report on the Deep-sea Keratosa collected by H.M.S. Challenger in 1889; these again opened up new chapters in zoology. The Challenger work is the crown of Haeckel’s studies as a specialist. To some extent the conclusion of it closes an epoch in his life.
We will only touch briefly on what he has done since. It has not yet passed into the region of history.
The latest years in Haeckel’s constructive work are characterised mainly by one idea. He had often been pressed to work up afresh the material of his General Morphology. He has not done so in the form that was expected, but chose a form of his own. In the first place he took the systematic introduction to the second volume, which had been the first able attempt to draw up the genealogical tree of the living world, branch by branch, and, with the material that had accumulated in the subsequent thirty-four years, built it up into a separate work. It had consisted formerly of 160 pages: now it formed three volumes of 1,800 pages. There were forty years of incessant study embodied in it. It had the title Systematic Phylogeny:[[7]] “a sketch of a natural system of organisms on the basis of their stem-history.” The first volume (dealing with the protists and plants) appeared in 1894; the second volume (dealing with the invertebrate animals) in 1896, and the third (dealing with the vertebrates) in 1895. Closely connected with it is his special systematic study of the stem-history of the echinoderms (star-fish, &c.), with particular reference to paleontology (The Amphoridea and Cystoidea in the Work in Commemoration of Karl Gegenbaur, 1896).
[7]. It has not been translated into English. A recent reviewer in Nature pronounced it to be Haeckel’s best work. [Trans.]
His academic colleagues had hardly begun to master this new phylogeny when Haeckel once more roused a general agitation by working up the philosophic nucleus of the Morphology in a more general form than he had done in the History of Creation. This new work was The Riddle of the Universe, “a popular study of the Monistic philosophy.”[[8]] It was, he declared, his philosophical testament. In a few months 10,000 copies of the work were sold, and a later cheap popular edition ran to more than 100,000 copies. It has also been translated into fourteen different languages. The controversy it excited has not yet died away. Already a supplementary volume, The Wonders of Life, has followed it (1904). Haeckel had been working in this department with great vigour for many years. He only made one appearance at a German scientific congress since the Virchow affair. That was on September 18, 1882, in quiet and uncontroversial form. A little excitement was caused amongst those who saw their salvation in keeping the gentle Darwin far apart from the impetuous Haeckel when he read a rather free philosophical confession of Darwin’s. Their tactics broke down as the deceased Darwin passed into an historical personality and disappeared from the struggle of contending parties. In 1892 Haeckel wrote with great vigour in the militant Berlin journal, the Freie Bühne, on the new alliance of the Church and political parties in Germany, criticising the political situation on general philosophical principles, and in opposition to Virchow’s spirit of compromise. In the same year he delivered at Altenburg a lecture on “Monism as a connecting link between religion and science.” In this he took a conciliatory line, and showed how his philosophic views could be reconciled with any really sincere pursuit of truth, whatever aim it professed to have. The address closed with the words: “May God, the spirit of the good, the beautiful, and the true, grant it.” However, both his criticism and his attempt at conciliation only led to further and more bitter attacks in certain quarters. His only reply was to bring out the first numbers of a fine illustrated work—a work that came from a quite different depth of his rich personality. This was the Art-forms in Nature [not translated], a collection of beautiful forms of radiolaria, sponges, siphonophores, &c., for artists and admirers of the beautiful. It was a work such as he alone could produce. “In the storm didst thou begin: in the storm shalt thou end,” he might have said to himself, in the words of David Strauss. The storm never left him. In its mood was flung off with ready pen the Riddle of the Universe. “Up, old warrior, gird thy loins!” as we read in Strauss.
[8]. Literally, the title is “World-Riddles,” or “World-Problems.” [Trans.]