Ernst Haeckel, 1890.
From a relief-portrait modelled by Kopf, of Rome.
As an old pupil of Virchow’s he applies the cell-theory to Darwinism—in the lower stage. The first living things, the roots of the great tree of life, consisted of a single cell. The logic of the cell-theory itself went as far as this. But is the individual cell the simplest of all living forms? Here there was a long-standing controversy as to definitions. At first the cell was regarded literally as a kind of chamber, like the cell in the honeycomb. Then it was found that the jelly-like, mobile matter within the cell-chamber was the essential element, the vehicle of life. Finally, it was possible to conceive this slimy substance without any firm membrane, without a chamber. Inside it, however, there was always (it was then thought) a thick and hard substance, the nucleus. If that was the fundamental and only really essential form, the Darwinian primitive and initial type of all terrestrial life must have been a similar drop of living matter with a solid central nucleus, a nucleated individual cell.
How could we pass from this primitive cell to the “inorganic,” the “lifeless,” the “dead,” the ordinary matter of stone, metal, and crystal? Haeckel believed that it was possible to make a step in that direction—not theoretically and philosophically, but practically—by showing that there were still living things on the earth that did not come up to the definition of a true cell, things that had not yet a nucleus in their soft gelatinous body. He discovered a number of tiny creatures that had a homogeneous particle of living matter for body, and showed no trace of a nucleus. The nucleus seemed to be the first beginning of an organ. It was altogether wanting in them.
To these most primitive of all living things he gave the name of monera, or the absolutely “simple.”
In these investigations it is very difficult to determine whether one of these tiny drops of plasm has a more or less transparent nucleus or not. It has often been affirmed in later years that these monera of Haeckel’s did not correspond to their description as living things without a nucleus, or creatures that were below the level of the true cell. It is, at all events, certain that there are to-day large numbers of the unicellular beings known as the bacteria in which no nucleus has yet been discovered by the most sceptical Thomas with the most powerful microscopes and best technical appliances of our time. It is the same with the chromacea (chroococci, oscillaria, nostoc-algæ), very lowly primitive plants whose whole body consists of a globule or granule of living plasm. However, here again the question is no longer of the first importance, now that evolution is entirely and generally accepted. At the time we are discussing the method chosen was all-important. Haeckel drew no conclusions without a solid basis. He believed he could give ocular proof of the existence of beings that were below the level of the cell. It was clear, at all events, that research in this department was only in its beginning, and could pour out wonder after wonder before the world recovered from its first fright over Darwinism.
Then there was the other end of the system—man. Here again it was not merely a question of concluding on philosophic grounds that man must have descended from the lower animals. Huxley had dealt in England with the question of man and the ape on the strict lines of zoology. He came to the important conclusion that man differs less zoologically from the highest apes, the gorilla and chimpanzee, than they do from the lowest apes. He proved his point by a technical study of skulls and brains, not from abstract philosophical principles. It could be demonstrated in the museum or zoological institute to any student with some knowledge of anatomy as easily as the existence and position of any particular bone in the skeleton. Haeckel went even further.
He constructed a genealogical tree stretching far below the apes. Next to them came the lemurs. The lemur, the ghostly nocturnal inhabitant of Madagascar, came from the Australian marsupial (kangaroo, &c.). The marsupial came from the duck-bill; the duck-bill from the lizard; the lizard from the salamander; the salamander from the dipneust or mud-fish; this from the sturgeon or the shark, and the shark from the lamprey. Below the lamprey, at the lowest limit of the vertebrate kingdom, was the amphioxus (or lancelet). This must have come from the worm—it was not at all clear how, at that time. And so the series ran on down to the unicellular protozoa, the amœbæ and the monera.
The construction of this tree would have been impossible for one who had not already done gigantic work. The whole of the new system of animals and plants, conceived in the form of a genealogical tree, had first to be sketched in outline. Then the narrower thread that led up to man, the Ariadne-thread of God-Nature, would gradually come to light.
Both ends of the system, the lower one in the monera, the upper one in man, were first thoroughly treated by him in 1865, and in part somewhat later. His exhaustive Monograph on the Monera was not published until 1868. Man’s genealogical tree was privately circulated at Jena in two essays in October and November 1865. They were published in the Virchow-Holtzendorff collection in 1868 (“The Origin and Genealogical Tree of the Human Race”). But in both cases the substance of the work, as an accumulation of facts, is much older. And this work was, of course, only possible in connection with a number of further conclusions: in regard to spontaneous generation, life and death, the crystal and the cell, the mathematical form of organisms, the nature and limits of individuality, the method of research, the new natural philosophy, God, and so on.
It was an enormous programme, with a Paradisaic freshness. Everything was new and great; and all came from one brain. There was only one man with whom he discussed his ideas as they formed, Carl Gegenbaur, who has undoubtedly had a great, if unconscious, influence on them. Haeckel’s grateful recognition of Gegenbaur’s help in later years was endless and touching. “Thou it was,” he writes to him a little later, “that led me to begin my academic teaching at our beloved Jena six years ago, at the Thuringian university in the heart of Germany, that has, like a beating heart, sent out its living waves of freedom and alertness of mind over Germany for three hundred years. At this nursery of German philosophy and science, under the protection of a free State whose princely rulers ever gave a refuge to free speech and have linked their names for ever with the reform movement, the golden age of German poetry, I was able to work in association with thee. Here we built up our common structure of science in the happiest division of labour, teaching and learning cordially from each other, in the very rooms in which Goethe began his studies of ‘the morphology of organisms’ a half-century before, and partly with the same scientific means, the germs of comparative and philosophic science that he had scattered. We have shared with each other as brothers the happiness and the sorrow that came in the hard struggle for life, and our scientific efforts have been so intimately blended and so mutually helpful, through our daily working and talking together, that it would have been impossible for either of us to determine the particular share of each in our spiritual communism. I can only say in a general way that the little my restless and impulsive youth could offer thee here and there is out of all proportion to the enormous amount I have received from thee, eight years my senior, a more experienced and mature man.”