Haeckel

At Easter, 1867, Haeckel returned to Jena through Morocco, Madrid, and Paris. He spent a few of the pleasant spring weeks at the Strait of Gibraltar and in the South of Spain. In the fine bay of Algeciras (opposite to Gibraltar on the west) the current of the Strait brought swarms of interesting medusæ, siphonophores, and other “plancton-animals” into his net. In his solitary walks through the mountain forests of Andalusia, in the incomparable Moorish palaces and the cathedrals of Seville and Cordova, Granada and the Alhambra, he gazed on that wealth of Spain in treasures of Nature and Art which had excited his boyish imagination in the vivid pictures of Washington Irving.

With his return home a crisis occurred in his career, from our biographical point of view, such as we find at one point or other in the lives of all great men. Up to the present the course of his life has advanced steadily onward, so that the simple chronological order afforded the most natural thread for our narrative. With this crisis his activity broadens out more. His ideas, almost all of which are presented in the General Morphology, form a great and continuous stem, which throws out a large or a small flower on one side or other, according to the stimulus received. His life crystallises about Jena; however many journeys he makes, he always feels that he will return to his centre at Jena. Nothing in his later career ever shook him from this ideal and personal base.

In the summer after his return to Jena, 1867, he married Agnes Huschke, daughter of the distinguished Jena anatomist. He shares the happiness of this second marriage down to the present day. Of their three children, the son is now a gifted artist at Munich; the elder daughter is the wife of Professor Hans Meyer, proprietor of the Leipsic Bibliographical Institute, who is particularly known in science by his ascent of the Kilimandschars; the younger daughter is still at home with her parents.

He never leaves the University of Jena—and it never abandons him. It is a kind of spiritual marriage. In 1865, when the sky was still free from clouds, he was invited to take a position at Würtzburg, his old school-place. He declined the invitation, and was then appointed ordinary professor at Jena. Then the evil days came. The conclusions of his Morphology were popularised by himself, and went out far and wide amongst the masses. People opened their eyes to find that this audacious scientist was making “war upon God” out of his zoology. At length the difficult question arises whether a mind of that type can be retained in the honourable position of official professor. The Philistines are in arms. The quiet, stubborn group, that has vegetated unchanged, like a demoralised parasitic animal, from Abdern to Schilda, through thousands of years of the free development of the mind, boycots the professor and his family for a time. The Philistines appeal from their safe corner to the authorities to intervene. Once, towards the close of the sixties, the situation threatened to become really critical. The head of the governing body of the university at the time was Seebeck, a distinguished man who by no means shared Haeckel’s views, but had a just feeling of Haeckel’s honourableness and mental power. In the middle of the struggle Haeckel approaches him one day, and says that he is prepared to resign his position, a sacrifice to his ideas. Seebeck replied, “My dear Haeckel, you are still young, and you will come yet to have more mature views of life. After all, you will do less harm here than elsewhere, so you had better stop here.” At Jena they still tell a similar story that happened on another occasion. A stern theologian presented himself in person at the chateau of Karl Alexander, Grand Duke of Weimar, and begged him to put an end to this scandal of the professorship of Haeckel, the arch-heretic. The Grand Duke, educated in the Weimar tradition of Goethe, asked, “Do you think he really believes these things that he publishes?” “Most certainly he does,” was the prompt reply. “Very good,” said the Grand Duke, “then the man simply does the same as you do.”

Haeckel remained a professor at Jena; and when the current subsided a little, he was not insensible of their liberality. He remained faithful to Jena, though even Vienna, amongst other places, offered him a position (1871). Under his guidance “zoological” Jena flourished like a poor orphan that has suddenly been enriched. At one stroke the university was lifted to the position of an intellectual metropolis for the whole of the young scientific generation of the last quarter of the century. The best of the younger men that fill the biological positions in Germany to-day (and many others) were educated under Haeckel. Many of these pupils became opponents of his eventually, but they all went through his system. He had a further satisfaction. He not only attracted the young men to Jena, but he conjured up as if by magic the financial resources for improving the external advantages of the place for teaching and working. His style of “zoology,” which was at the same time “natural philosophy,” brought people to his assistance who would never have been won by a narrowly technical zoologist, no matter how learned he was. Twice men were induced “for his sake”—that is to say, induced by the magnetic force of his charming personality—to leave large legacies to be spent on the university under his direction; once it was the Countess Bose, another time Paul von Ritter of Basle. Ritter alone gave sufficient to found two professorships at Jena for the express purpose of teaching the science of phylogeny that Haeckel had created.

All through the period of his long stay at Jena that followed we trace a series of continual holiday journeys. In these journeys he used to collect the best material for his professional research, following the method he had learned from Müller at Heligoland, and had practised at Messina and Lanzarote. At the same time these travels were, like the earlier ones, the bath of eternal youth and health for “the other soul in his breast”; the artist, the lusty wanderer, I might almost say the inveterate Bohemian in him, was then allowed to have his spell of song and gaiety. In Jena he took deeper and deeper root as time went on. There was something in him in this respect of a Persephone impulse, an alternation of winter and summer in his life. When the days of hard and wearing work were past, he would have to rush away into the free air, down to the blue sea, to far and happy Nature. “Here I am a man—dare be a man.” The duty of the zoologist of Müller’s school to go down to the sea to work came to his rich temperament, which included so much more than mere “professional reasons,” with a splendid sense of Persephone-life: half his time in the cold North studying animal skeletons and dead bones by the burning lamp, the other half in the glare of the sun of reality, in living nature at its best. I will only quote summarily a few dates of these travels. In 1869 he spent the autumn vacation in Scandinavia. In 1871 he was in the island of Lesina in Dalmatia, where he, the arch-heretic, lived in a monastery with a jolly abbot. From beautiful Ragusa he made an interesting excursion to Cattaro and Montenegro. In 1873 he went to Egypt and Asia Minor, visiting Athens, Constantinople, Brussa, and the Black Sea. The culmination of this journey was a visit to the splendid coral banks of Tur, in the Red Sea. The Khedive, Ismail Pacha, put a Government steamer at his disposal for the journey. The excursion has been superbly described by Haeckel himself in the little volume, The Corals of Arabia (1876). The same volume contains the first specimens of his landscapes in water-colour. He spent the spring of 1875 in Corsica and Sardinia. On that occasion Oscar Hertwig discovered, in his presence, the process of fertilisation in the sea-urchin; his discoveries will long remain a turning-point in the history of our knowledge of sexual generation (one of the deepest mysteries in nature). In the autumn of 1876 he was at work on the coast of Great Britain, and reached as far as Ireland. In the spring of 1877 he was at Ithaca and Corfu; in the autumn we find him on the Riviera. In 1878 he went first to Fiume and Pola on the Adriatic, and afterwards on an Atlantic excursion to Brittany, Normandy, and Jersey. In the autumn of 1879 he was in Holland and Scotland.

In 1881 he made the second longest journey of his life. He secured permission to absent himself from the university for six months, and went to Ceylon. He left Jena on the 8th of October, and did not return until April 21, 1882. The traveller and æsthete in him revelled in this first plunge into the tropics. How he was taken to the enchanted land of India in the Lloyd steamer Helios, a pretty reminiscence of the “heliozoa” (sun-plants), a name he had himself invented; how he greeted his beloved medusæ in their beautiful tropical forms of the Indian Ocean; how he lived in the execrable but thoroughly tropical and interesting Whist-Bungalow at Colombo, where mysticism and an unholy joy in card-playing occupied him until philosophic zoology came to crown and redeem everything; how he set up his zoological laboratory far from the world at the Cingalese village of Belligemma (which he interpreted bella gemma, the “pretty jewel”), and fished with his Müller-net for radiolaria, medusæ, and siphonophoræ, for six whole weeks, to the intense bewilderment of the naked children of the palms; how he at last penetrated into the wildest virgin forests of Ceylon, where one heard the heavy tread of the elephant and the roar of the panther—all this he has described in his Visit to Ceylon, the freshest expression of his temperament, which belongs utterly to the free, artistic half of his life, when Persephone has her summer days in the land of flowers.

He himself regarded this journey, happy and favoured to the very last minute, as a crown and conclusion of his travels that could never be surpassed. But many a long hour was to be spent in travel after that, and he was to make one journey that left Ceylon far behind him in the Indian Ocean. In the spring of 1887 he made a pilgrimage to the “Holy Land,” Jerusalem and the Dead Sea, Damascus and Lebanon. On this journey he spent a delightful month on the island of Rhodos. In 1889 he had a pleasant time on the beautiful island of Elba. In 1890 he visited Algiers, where his innocent sketches and his anatomical knife brought suspicion on him; they arrested him and threatened to shoot him as a spy. He has described the incident in his genial way in his Algerian Reminiscences which is, unfortunately, lost in a back number of some magazine or other, like so many of the sketches of his travels. In 1897 he travelled over the whole of Russia, from Finland to the Caucasus, and visited Tiflis, Colchis, and the Crimea. In the autumn of 1892 he accompanied Sir John Murray, of the Challenger expedition, on a small deep-sea investigation on the coast of Scotland. In the spring of 1893 and 1897 he was at work once more in his beloved Messina, where he was now honoured as a world-famous guest. In the autumn of 1899 he climbed the Sabine and Corsican hills. As the second decade after his first journey to the tropics came to an end, he seemed to regard all he had done so far as a small payment on account. In his sixty-sixth year he felt the “home-sickness” for the tropics once more with such intensity that he quickly made up his mind to go as far as the equator. He left Jena on August 21, 1900, and (after a brief visit to the exhibition at Paris) took ship at Genoa, on September 4th, for Singapore. His beloved Italy had provided part of the cost of the journey. In the previous year the Royal Academy of Science at Turin had awarded him the Bressa prize (consisting of 10,000 lire) on account of his Systematic Phylogeny. Once more the tropics revived the great impression made on him in his earlier visit. This time he spent only a few hours in Ceylon, and sailed further south. He landed at Singapore on September 27th, and sixteen days afterwards went on to Java, and thus crossed the equator at last. He enjoyed to the full the charms of the landscape with its volcanoes and virgin forests, during his stay with Treub at Buitenzorg, at Tjibodas, and during his long journey across the greater part of the island. At Tjibodas he celebrated the close of the nineteenth century [German calculation] by painting a fine water-colour of the smoke-canopy over the summit of the volcano Gedeh, touched and gilded by the east rays of the sun on the last day of 1900. On January 23, 1901, he went from Batavia to Sumatra, crossed the Sunda Strait in sight of the famous volcanic ruins of Krakatoa, and spent six weeks in Padang on the south-west coast of Sumatra. This delay was largely involuntary, and due to an injury to his knee, caused by stumbling over a rail during a visit to an engineering establishment; but the time was by no means lost in the middle of such glories. On March 31st he landed in Europe (at Naples) once more, after a safe voyage. The notes he made during his journey yielded another charming work, Letters from the East Indies and Malaysia (1901). His spirit of enterprise is inexhaustible, and still continues.

Within this frame of his career we have now to study a growth of ideas and a continuance of research that tell of vigour, consistency, and success in every line. It unfolds logically like a great work of art.

The General Morphology stands at the parting of two ways. It afforded a programme of an infinite amount of fresh technical research—the elaboration of his studies in detail, of promorphology, of his theory of individuality, and of the phylogenetic system of living things; and the strengthening of the laws of evolution, especially the great biogenetic law. On the other hand, there was the purely philosophic work to be done: the gathering together of the general threads that ran through his work, and the building of a new philosophy of life, based on a new story of creation, from the atom to the moneron, from the moneron to man, and the whole to be comprised and contained in God. In a word, he might proceed in either of two ways from the Morphology: he might construct academic zoology afresh, or he might write a work on the new God.

When he came home from Lanzarote, the two ways seemed to coincide in front of him; his work had, indeed, opened them out as one. But external circumstances intervened. As things are, it was only his academic colleagues that had any right to the new biology. A new book on God and creation would go out to “the publicans and sinners.” Interest must be lit up amongst the people at large, where there was as yet only the faintest spark. It appeared, moreover, that most of his academic colleagues in 1867 had no wish to enter on the new path he had opened out. A new generation would have to grow up first. The Morphology, from which Haeckel on his travels had expected at least a revolution, met at first with an icy silence. There was hardly any discussion of it, and no excitement whatever. Haeckel quickly made up his mind. He must turn in the other direction. Gegenbaur consoles him. He has given too much—twenty dishes instead of one. He must serve up the best part of the work on one dish, and it will be taken. Haeckel agrees with him to some extent, but his heavy technical artillery cannot be simplified so easily as that. The only possible thing to do is to give an extract of it, which will make the broad lines of the system clear. But as soon as that is done, he sees that the extract is still only the general philosophical part of it, and will not appeal to the general public.

It was such reflections as these that led to the writing of his History of Creation, a popular work.^[5]

The chapters of this work were first delivered orally to students, in the form of lectures, and formed a kind of introduction to morphology. The lectures, retaining their lighter form, were then combined to make the book. It was published in 1868, a small volume in a very primitive garb. The success of the work was unprecedented.

Zoology and botany were treated philosophically in the Morphology. That did not suit the professional scientists, who (as I said) crossed themselves when they saw “natural philosophy.” In the History of Creation the great problems of philosophy are dealt with successively on Darwinian lines, from the zoological and botanical point of view. It was like the sinking of a deep well amongst general thoughtful readers. People felt at last what a power science had become. The old riddles of life were studied in a new light with the aid of this book. There was no predecessor in this field. Haeckel was absolutely the first to appeal to the general reader in this way. It is true that what he gave them was, strictly speaking, only an extract from his own Morphology, especially the second volume. But as he now arranged his matter chronologically, he converted his outline of a world-system into a “world-history”—a real “history of natural creation.” In the “Pictures of Nature” in the first volume of his Cosmos Humboldt had tried to bring the natural world before his readers as a great panorama, to be taken in at one glance. But he strictly confined his study of nature to the things that actually exist; how they came to exist was not, he intimated, a subject of scientific inquiry. Haeckel proceeds to this further task. His panorama of nature does not stand out rigidly before us; it develops, under the eyes of the observer, from the formless nebula to the intelligent human being. Even on the surface this was seen to be a prodigious advance. Very plain, but very attractive, it makes its way by the force of its convincing dialectic, and places no reliance on the fireworks of rhetoric. The subtle power of it lies in the arrangement of the facts, which suddenly assume the form of a logical chain instead of being a shapeless chaos. Even if all the main ideas of the work were false, we should be compelled to regard it as one of the cleverest works that was ever written, from the dialectical point of view. But the essence of this cleverness is the way in which the grouping of the facts is made to yield the philosophic evolution, which is the thoughtful basis of the work. As the world proceeds in its natural development from the nebular cosmic raw material until it culminates in the ape and man, the reader finds himself at the same time advancing along a series of general philosophic conclusions with regard to God, the world, and man. If at the end he has retained the whole series of what are to him more or less new scientific details, he is bound to find himself caught in a strong net of philosophic conclusions.

In view of all this we can easily understand the different reception that the book met with from friend and foe. People who had already assented to the main issues of the work on general grounds of probability, were delighted to find these issues decisively established by the plain facts of science. On the other hand, those who would have none of Haeckel’s philosophy now felt compelled, in view of this dreadful work, to call these alleged facts of science themselves into question. In face of this hostility it was some disadvantage that the History of Creation contained a vast amount of technical material (such as the genealogical trees, the Darwinian laws, the explanation of the facts of embryology, &c.) that could only be presented summarily in it, while the proper technical description and justification of them was buried in the thick volumes of the Morphology. Haeckel said, over and over again, that a certain thing had been so fully established by him scientifically in the other work that he was now at liberty to take it as a fact; and he accordingly built it up as such without prejudice into the compact structure of the popular work. Readers who wanted to go further into the discussion of these facts had to look up the relevant passages in the larger book. But the great bulk of his opponents—amongst whom we must count even many professional scientists—had never read the two volumes of the Morphology. They merely took the brief statement in the History of Creation, which was really little more than a reference, and made a violent attack on the “fact” it was said to convey.

This led to a great deal of confusion. As in this case a controversy over some petty zoological detail was always a “struggle about God,” and so agitated the opponent down to the most secret folds of his philosophy, the usual consequences did not fail to put in an appearance. Haeckel was branded and calumniated personally. There has never been any apostle in the world that some sect or other has not decried as a rogue and evil-doer, simply because he was an apostle. Wherever Haeckel has made use of any material that did not seem to be absolutely sound in every respect, he was not simply accused of making a mistake, not even of ignorance, but the whole thing has been put down at once to dishonesty and the worst type of bad faith.

One should bear in mind how very generally pioneer work of this kind is liable to err. Further, in the History of Creation there is the danger involved in the popular presentation of the results of scientific research. Any man who has written popular works, or delivered lectures to the general public, knows what this means. There is little common measure between them. The truths of science are in a state of constant flux; it is of their essence to be so. To fish out a piece from this stream, fix it, and magnify it for the public with a broad beam of light, really amounts in principle to an alteration of it; it is putting a certain pressure on things, and giving them an arbitrary shape. The work of popularising truths is so holy a thing in its aim that this risk has to be run. We must take things as they are. We have two alternatives: either not to popularise at all, or to take the apparatus with all its defects. We can diminish these according to our skill; but there is a subjective limit to this skill in all of us.

The first edition of the History of Creation—Haeckel’s first attempt at popularising—had a good deal of inequality in this respect. To begin with, the book had the air of an extempore deliverance. Its success was very largely due to its being cast in this form. But there was a good deal that could be improved here and there, and was improved in the later editions of the work. In the tenth edition, as we now have it, it is a splendid work in regard to the illustrations, for instance. But the first edition was merely provided with a few very crude woodcuts in outline. Some of them were very clumsy. In comparing different embryological objects the same blocks were used sometimes, and this would give rise to misunderstanding in the mind of the reader. For instance, there was question of demonstrating that certain objects, such as the human ovum and the ovum of some of the related higher mammals, were just the same in their external outlines. This fact is quite correct and established to-day. If I draw the outline, and write underneath it that as a type it is applicable to all known ova of the higher mammals, including man, there is no possibility of misunderstanding. But if I print the same illustration three times with the suggestion that they are three different mammal-ova, the general reader is easily apt to think, not only that they are identical in the general scheme of this outline, but also in internal structure. He imagines that the ova of man and the ape are just the same even in their microscopic and chemical features. This leads to a contradiction between the illustration and what Haeckel expressly says in the text. We read that there is indeed an external resemblance in shape between these ova, but that there is bound to be a great difference in internal structure, since an ape is developed from the one and a human being developed from the other. It would have been better if the general reader, who is not familiar with these outline pictures, had been more emphatically informed in the text below the illustration that even the outline is to be taken as a general and ideal scheme. In this sense we must certainly admit that the illustration was bad, since it would lead to a misunderstanding of the clear words of the text. But what are we to say when the opponents of Haeckel’s views viciously raise the cry of “bad faith” on the ground of a few little slips like this, and suggest that he deliberately tried to mislead his readers with false illustrations? Amongst the general public, in so far as it was hostile to Haeckel, the charge blossomed out into the most curious forms. Some declared that the whole story of a resemblance between man’s ovum and embryo and those of other animals was an invention of Professor Haeckel’s; others—we even read it now and again in our own time—went so far as to say that the human ovum and embryonic forms only existed in Haeckel’s imagination. All these wild charges are of no avail. The human ovum, which corresponds entirely in its general scheme to that of the other higher mammals, was not discovered in 1868 by the wicked Haeckel, but in 1827 by the great master of embryological research, Carl Ernst von Baer. The considerable external resemblance, at certain stages of development, between the embryos of reptiles, birds, and mammals, including man, was decisively established by the same great scientist. These really remarkable stages in the development of the human embryo, during which, in accordance with the biogenetic law, it shows clear traces of the gill-slits of its fish-ancestors, and has a corresponding fin-like structure of the four limbs and a very considerable tail, can be seen by the general reader at any time in the illustrated works of His, Ecker, and Kölliker (Haeckel’s chief opponents) or in any illustrated manual of embryology, and their full force as evolutionary evidence can be appreciated. Any man that constructs his philosophy in such a way that, in his conviction, it stands or falls with the existence of these embryonic phenomena, is in a very delicate position, apart altogether from Haeckel. His philosophy will collapse, even if the History of Creation had never been written.

These curious discussions did not seriously interfere with the success of the book. In thousands and thousands of minds, in 1868, this little work proved the grain of seed that led on in time to serious thought. From that time onward Haeckel knew that he had not only scientific colleagues and academic pupils, but a crowd of followers. When he made an excursion into the northern part of the Sahara, as far as the first oasis, twenty-two years afterwards, he met an artist there. They talked philosophy, and the man, not knowing Haeckel, naïvely recommended him to study the History of Creation as likely to give him most help. The little incident shows us something of the great pioneer work done by the volume, something of its spiritual circumnavigation of the globe.

Thus the spiritual nucleus of the General Morphology is introduced, with great ability, to a much wider circle than Haeckel had dreamed of when he gave the Morphology to his colleagues. But the agitation gradually spread into academic circles. On the whole the Darwinian ideas pressed in everywhere by their own irresistible weight. Haeckel’s more particular concern, however, was to secure the recognition of one single point in the larger group of ideas—the great biogenetic law. This was for many years the pivot on which almost all the discussions with him and about him turned.

He himself did not at first conceive his law as a matter of controversy, but as a method that must be brought into a position of practical utility. An opportunity to do this arose immediately.

While he was at Lanzarote he began to take an interest in a second group of lowly animals besides the siphonophores, namely the sponges. When the general reader hears the word “sponge” he must modify his ordinary ideas a little. In the present instance he must not think of the plants, belonging to the fungi-group, such as the morel and cognate forms, that are often called “sponges” in common parlance. He must think rather of the sponge he uses in his bath. The bath-sponge is a structure made up of very tough, elastic, horny fibres. This structure is originally the skeleton, as it were, of certain animals that are known as “sponge-animals” or, briefly, sponges; they have nothing to do with the spongy mushrooms I spoke of. At the same time these socially-living sponges are such curious creatures that it was disputed for a long time whether they were real animals or not. There was a second controversy in regard to them as to where the “individual” began—what was a single animal, and what a co-operative colony of animals. The latter point alone would have been enough to direct Haeckel’s attention to this group after he had, in the case of the siphonophores, gone so deeply into the mystery of combined individuals, forming a new “state-individual.” His own opinion eventually was that as a matter of fact in the majority of cases the whole sponge is a stock or colony of separate sponge individuals closely connected together. They had not, indeed, anything like the ingenious method of division of labour that we find in the social medusæ; in fact, the sponges are in all respects much more lowly organised animals than the medusæ. But they were certainly true animals. And in the middle of his efforts to prove this Haeckel travelled into an entirely new field of research, lying far beyond the theory of individuality.

As there is an enormous number of different sponges, he had confined his studies from the first to a single group of them that might be taken as typical. He chose the calcispongiæ (calcareous sponges), which had been the least studied up to that time. As the name obviously implies, these sponges form their internal framework or skeleton, not of elastic horny fibres like the common bath-sponge, but of solid calcareous needles or spines. They secrete these out of the soft substance of their bodies just as the radiolaria do their pretty siliceous houses. Haeckel was engaged for five years, from 1867 to 1872, in a profound and careful study of the natural history of the calcispongiæ. Then he published the results in his Monograph on the Calcispongiæ, consisting of two volumes of text and an atlas of sixty fine plates.

The first result was that the calcispongiæ afforded a splendid proof of the impossibility of drawing sharp limits between species in the perpetually developing animal world. In their case the different varieties passed constantly out of each other and back into each other in a way that would have made a classifier of the old type distracted. But Haeckel had travelled far beyond the position of his boyhood, when he had timorously concealed the bad species that would not fit into the system. He said humorously that in the case of the calcispongiæ you had the choice of distinguishing one genus with three species, or three genera with 239 species, or 113 genera with 591 species. All this confusion was saved by the Darwinian idea of not setting up absolutely rigid classes, families, genera, and species. But even this was not yet the essential point.

As he had done in the case of the siphonophores, Haeckel endeavoured to derive as much information as possible from the “ontogeny,” or embryonic development, of the calcispongiæ. He established in some cases, it seemed to him, that a single calcisponge-individual at first and up to a certain stage developed from the ovum in the same way as a medusa or a coral or an anemone. The fertilised ovum, a single cell, divided into two cells, then several, and at last formed a whole cluster of cells. In this cluster the cells arranged themselves at the surface, and left a hollow cavity within. Then two layers of cells were formed, like a double skin, in the wall of this vesicle, and an opening was left at one spot in the wall of it. Thus we got a free-swimming embryo, with a mouth, an external skin, and an internal digestive skin or membrane. Then the creature attaches itself to the floor of the sea and becomes a real sponge, partly by developing along its characteristic lines, and partly (in most cases) by producing other sponges from itself in the form of buds, like the siphonophore, and so forming an elaborate colony, to which we give collectively the title of “a sponge.” These facts led to the following reflections.

This original development from the ovum, first into an embryo with the form of a small globe or, more correctly, an oval body consisting of two layers of cells and having a hole at one pole—in other words, a creature with nothing but skin, stomach, and mouth—was found, curiously enough, in other animals besides the medusæ, corals, and sponges. We have the same course of development in representatives of the most varied groups of animals. There are worms, star-fishes, crabs, and snails that develop in the same way. In fact, it was proved in this very year (1867) that the lowest of the vertebrates, the amphioxus (or lancelet), develops in the same way. And this was not all. In the ontogeny of all the higher animals right up to man (inclusive) we find a state of things that most closely resembles the same development. At all events, the fertilised ovum gives rise in all cases to a cluster of cells; this cluster forms something like a flattened or elongated vesicle with a single-layered wall; the single layer of cells is doubled, and in the building up of the body one half makes the external coat or skin and the other half the internal lining or membrane. Haeckel reflected on the whole of the facts, and drew his conclusions. This very curious agreement in the earlier embryonic forms must be interpreted in terms of the biogenetic law. In the case of the higher animals the forms have been profoundly modified by cenogenesis. In the lower animals they are almost or altogether a pure recapitulation of the real primitive course of the development of the animal kingdom. In the earliest times animals were evolved in something like the following way. First, the primitive unicellular protozoa came together and formed crude social bodies, clusters of cells that kept together, but had no special division of labour. As all the members in the cluster pressed to the surface, in order to obtain their food, they came to form, not a solid mass of cells, but a hollow vesicle with a wall of cells. Then the first division of labour set in. Certain cells, those that were situated at the anterior pole, and so were better placed to receive the floating food as the animal moved along, became the eating-cells of the group; they provided nourishment for the others, as the nutritious sap circulated through all the cells in the cluster, as we find in the case of the siphonophores. As these feeding-cells multiplied rapidly at the fore part of the animal, a depression was formed at that pole of the body. In the end the ball or vesicle was doubled in upon itself, until it came to have the form of a cup with a double-layered wall. Externally were the cells in the skin that effected movement and feeling, and afforded protection; inside, forming the internal wall, were the eating- or stomach-cells. An opening remained at the top—the opening of the cup or vase-like body. The food entered by it: it was virtually the “mouth.” Thus was formed a primitive multicellular animal with division of labour. If we imagine it attaching itself to the bottom by its lower pole, we can see that it would easily become a sponge of the simplest kind, a polyp, a coral, or, detaching itself once more, a medusa. If we imagine it swimming ahead in the water or creeping along the ground in such a way as to assume a bilateral symmetrical structure, like a tube, with right and left, back and belly, and an anus behind, we have a worm. This worm developed, under the action of the Darwinian laws, into a star-fish in one case, a crab or insect in another, a snail or mussel in another, and lastly into the amphioxus, which led on through the vertebrates to the human frame. But the mysterious series of forms always remained in the development of the individual from the egg, pointing more or less clearly to the earlier stages: ovum, cluster of cells, ball, two cell-layers in a cup-shaped form, skin, stomach, and mouth. All animals that exhibit this primitive scheme belong to one great stem. It was not until this skin-stomach-mouth animal was formed that the tree branched out—evolving into sessile, creeping, swimming, and other forms. Let us give a name to this phylogenetic (ancestral) form, which stands at the great parting of the ways in the animal world, as embryology proves. Leaving aside its innumerable relatives in the primitive days, it must have differed essentially from all other living things at the time—all the protists and the plants—by its possession of a skin, stomach, and mouth. Gaster is the Greek for stomach. Let us, therefore, call this primitive parent of all the sponges polyps, medusaæ, worms, crustacea, insects, snails, mussels, cephalopods, fishes, salamanders, lizards, birds, mammals, and man, the gastræa, the primitive-stomach or primitive-gut animal. The corresponding embryonic form may be distinguished from it as the gastrula. There are still many living species of animals that are very little higher in organisation than the gastræa-form. The Pemmatodiscus gastrulaceus, discovered by Monticelli in 1895, corresponds entirely to it. And the gastrula is found, as I said, with astonishing regularity in its precise gastræa-form in representatives of all the higher groups of animals.

That is an outline of the famous gastræa-theory, that Haeckel discovered when he was engaged in studying the calcisponges. It was first published in his large Monograph on the Calcispongiæ in 1872, elaborated in his Studies of the Gastræa-theory in 1873, 1875, and 1876 (published in one volume in 1877), and generally expounded, together with the biogenetic law, in (amongst other works) his polemical essay, “The aims and methods of modern embryology” (1875). This discovery, in Haeckel’s opinion, now made the biogenetic law a real search-light in the exploration of the obscure past. It indicated a third critical point in the great genealogical tree. Already we had the root (the monera) and the crown (man); now we had the point from which the various real animal stems radiated like the umbellate branches of a single large bloom. Through it the Darwinian system had been converted into the greatest practical reform of animal classification. If this gastræa-theory was correct, it was an incalculable gain for zoology. The difficulty of it, on the other hand, lay in the infinite modifications of the embryonic processes in detail that had been brought about by cenogenesis; almost everywhere this had more or less obscured the original features. On the whole it gave rise to the greatest and most far-reaching discussion that has taken place in zoology for the last thirty years, apart from the Darwinian theory itself. To-day, at the close of these three decades, there are only two alternatives. One is that there is still an absolutely mysterious and hidden law of ontogeny, that compels countless animals over and over again to pass through these embryonic forms and assume a likeness to the gastræa. After all the eagerness with which the whole school of embryologists opposed to Haeckel have sought, up to our own day, to establish such a direct law, we have not yet got the shadow of a clear formulation of it. The other alternative is that Haeckel is right in believing that he has discovered the correct formula in his phylogenetic interpretation of embryonic processes in accordance with the biogenetic law. If that is so, the gastræa-theory is the crown of all his labours in technical zoology proper. Let us wait another thirty years.

The scientific controversy over the gastræa-theory was in full swing when Haeckel entered upon another bold experiment in the direction of the biogenetic law. He thought it would be useful, instead of framing wider hypotheses, to take one single instance of one of the highest animals, and trace the whole parallel of its embryonic and ancestral development down to its finest details. It would serve as an excellent object-lesson. He would take it, not from some remote corner of the system, such as the sponges or medusæ, but from the very top of the tree, where palingenesis and cenogenesis seemed to have culminated in an inextricable confusion. But what example could be more appropriate and effective than the most advanced of all living things—man. He would write a monograph on man on an entirely new method; would show ontogeny and phylogeny confirming each other down to the smallest detail. It was another great enterprise. And this particular subject was so interesting that it would appeal strongly to the general readers of his History of Creation as well as to the academic scientists. Man was a subject of such obviousness and importance to the layman that in this case there was really no professional limitation of interest at all. Every detail in the most technical treatment of the subject would be taken into account, and evoked his strongest sympathy.

When Haeckel had fully matured this plan, he produced his Anthropogeny.^[6] The word, founded on the Greek, means the “genesis” or “evolution of man.”

The work is a very able combination of two different aims. On the one hand it affords the technical student the outline of a wholly new and distinctive manual of human embryology (up to a certain extent) and general anatomy; and this is intimately bound up by his method with a kind of historical introduction to general anthropology. At the same time the book forms a second part of the History of Creation. It builds up the most important chapter of the later work, from the philosophical point of view, namely, that which deals with the origin of man, into a fresh volume; and it represents the first popular treatment of embryology on broad philosophic lines—a thing that had never been attempted before. Springing up from this double root, the work is certainly one of the most successful things in the whole of Haeckel’s literary career. Moreover, it is not merely a compendium of a larger work, like the History of Creation. In spirit and form it is an original work, and gives his very best to the reader. As far as its general effect is concerned, the double-address of the work has had its disadvantages. The academic students who were hostile to it have once more selected for attack certain excrescences and gaps that were merely due to the exigencies of popular treatment. On the other hand, the general reader found it, in spite of the popular form, on which Herculean labour had been spent—one has only to think of the details of embryology—a book that was not to be “read” in the ordinary sense of the word, but studied. The first edition appeared in 1874. A fifth edition has now been published, equipped with the finest illustrations, both from the artistic and the scientific point of view, that have ever appeared in a popular work on embryology. We find in the Anthropogeny all that the nineteenth century has learned or surmised with regard to the ancestral history of mankind. Even the gastræa-theory—the gastræa belonging to man’s direct ancestry—is dealt with in popular fashion as far as this was possible.

When the Anthropogeny was published Haeckel’s public position became more stormy than ever. In professional circles a number of the embryologists had taken up an attitude of opposition to him; the most heated of them attacked his popular works continually on the ground that he was popularising, not the real results of official science, but his own personal opinions. There was a great deal of truth in that. The only question was, which would stand best with the future, his or their personal opinion? It does not alter the subjectivity of opinions that a few people here and there combine and pretentiously constitute themselves into a “science.” Posterity will deal coolly enough with their collective decisions. It will take every man of science as an individual, and merely ask which of them came nearest to the truth. The name, the official science, will pass into the grave with many titles and decorations. All that will remain in men’s minds is the star of the personality in its relation to the great constellation of contemporary human truth. However, as regards the particular embryological attacks of these opponents, it seems to me to-day especially characteristic that such people are more and more abandoning the idea that it is only a question of contesting certain particular deductions of Haeckel’s within the limits of Darwinism. They find themselves increasingly compelled to throw Darwinism overboard altogether. Instead of its attempts to explain phenomena they are putting forward a confused claim of “direct mechanical explanations,” or relying on the sonorous old phrase, started in 1859, an “immanent law of evolution,” or retreating into a despairing attitude of “I don’t know.” These clearer divisions will make it very much easier for posterity to pass its judgment on the situation.

After the embryologists we have a considerable group of opponents on the anthropological side. The objections of these anthropological critics have in the course of time narrowed down to the single argument that no transitional form between man and the ape has yet been discovered. And for many years now this position has not been held on serious scientific grounds, but rather on ingenious and strained hypotheses. Because we now have, in the bones found at Java by Eugen Dubois in 1894, the remains of a being that stands precisely half-way between the gibbon and man. Hence what is called the anti-Darwinian and especially anti-Haeckelian school of anthropology to-day is mainly distinguished for its preference of more risky and more subtle hypotheses instead of plain conclusions from obvious facts. Finally, there is the theological opposition to Haeckel that increased with every book in which he put his ideas before the general public and helped them (in their boundless professional wisdom) to realise the danger of the situation.

The year 1877 was a critical one in this respect. In the middle of his struggles Haeckel retained all the simplicity of his nature. He saw that the idea of evolution was triumphing over all obstacles and rapidly securing the allegiance of the best men of the time. On the 18th of September, 1877, he spoke of this with unrestrained delight at the scientific congress at Munich. He described the theory of evolution as “the most important advance that has been made in pure and applied science.” Then Rudolf Virchow delivered a speech at the same congress.

There is no doubt whatever that in the period since Virchow had indicated a neutral field in 1863, in which science might effect “its compromise,” Haeckel had boldly invaded that province. In the previous year he had published a little work called The Perigenesis of the Plastidules, or the Generation of Waves in Vital Particles. It was delivered in lecture-form at the medical-scientific congress at Jena in November, 1875, and then printed on the occasion of Seebeck’s jubilee, May 9, 1876. Possibly it is the least known of all Haeckel’s works, though in my opinion it is one of the most valuable in regard to the prophetic breadth of its intuition. It essays to establish a theory of heredity. In dealing with this deepest mystery of life psychic factors are pressed into service without reserve. Not only is the cell-soul put into prominence, but the cell in turn is resolved into a number of smaller units, the plastidules. Each plastidule is then conceived as a psychic unity. The souls of the plastidules are endowed with memory; that is the root of heredity. They learn; that is the psychological expression of adaptation. The little work offers a suggestion of a psychology of Darwinism that may very well become the nucleus of the whole Darwinian structure in the twentieth century. But at the time it was quite obvious that a man with such ideas as these was breaking with lusty fist through the sacred net that spread before Virchow’s reserved province. The hour had come, therefore, for Virchow to feel that he must expel the idea of evolution from the whole field of science, and not merely from embryology and anthropology.

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).