When Haeckel had massed his material he had first to create the necessary terms for arranging it distinctly. In the language of the old legend, he called the day day, and the night. To the story of ancestral development, or the evolution of the stem, he gave the name of phylogeny, or stem-history (phylon = stem). The word circulates very widely to-day. The story of the development of the individual until it reaches maturity was then called ontogeny (on = being), which coincides generally with embryology (though it may also include the growth of the child). The law then ran: Ontogeny is an abbreviated and frequently disarranged epitome of phylogeny. Special attention was drawn to the qualifications “abbreviated” and “disarranged.”
Here again two fresh names were invented. In so far as the embryonic development is a true recapitulation of the stem-history, it is called palingenesis, or repetition of the ancestral traits. When the development is altered by new adaptations it is called cenogenesis, “foreign” or “disturbing” development.
It has been objected by small-minded critics that Haeckel forces nature to mar its own work. The real meaning is quite clear if we bear in mind the blunder of Oken. In this case “disturbed development” is merely an expression of the fact that the laws we invent are ideal forms, and not always convenient realities. We learn by heart that the earth is a globe, and its orbit is an ellipse. Neither of the two propositions is strictly accurate; no mathematical figure even has objective reality. By the sheer attraction of the water of the ocean to the continents the earth has an irregularity of shape that it is barely possible to express in words. To call the path of the earth round the sun, constantly altering as it does, and still further complicated by the sun’s own movement, a real ellipse is the greatest nonsense conceivable.
In this sense every natural law is subject to disturbances, though these in turn are the outcome of natural laws. If we do not cavil over the name, we find that the idea it stands for is of the greatest consequence for any further use of the biogenetic law. Unless it is borne in mind, the law, especially in the hands of the inexpert, falls into hopeless confusion. We read so often that the ancestral history is identical with the embryonic development. The one is a recapitulation of the other. This supposed law is then applied in psychology, æsthetics, and many other directions. If it succeeds, there is jubilation. If it does not succeed (as it does not in a thousand cases), the whole blame is thrown on Haeckel. People discover that “the biogenetic law breaks down here,” and they throw over Darwinism altogether.
The second volume of the Morphology is the standing palladium against all this nonsense. It marks off the real readers and followers of Haeckel from the superficial talkers who run after him because he is famous, and will leave him unscrupulously for any other celebrity of the hour.
The book must be read. Even in this second volume an incredible amount of matter is compressed. An introduction, consisting of a hundred and sixty pages of small type, gives us an idea of the new system. This is the first scheme of a real “natural classification” of living things. From this we pass to special morphology. But this fearless sketch of the specialised genealogical tree, according to the new ideas, puts general morphology in its true light. We are made to feel that it is not all mere theory. To-morrow—nay, to-day—the whole practice of zoology and botany will have to be remodelled on the new principles. Off with the roof of the ark! The whole museum must be cleared out. We want new divisions, new labels. The old controversy between the Nominalists and the Realists seemed to have come to life once more. How students had played with the word “affinity” as a symbol. The lemurs were “related” to the apes, and to other groups of mammals. The star-fishes were related to the sea-urchins, to the encrinites. The word had, in fact, led to a certain amount of arrangement; the stuffed or dried or preserved specimens in the museum were placed side by side. Suddenly the whole thing became a reality. The things that were “related” to each other had really been connected historically in earlier ages. The lemurs were the progenitors of the apes. Behind them were a series of other mammals. Star-fishes, sea-urchins, and encrinites, formed a definite branch of the great tree, and were historically connected; not symbolically, but in a real extinct common ancestor.
It was a vast work. A single man had at first the whole kingdom in his hands, had to reject the old lines of demarcation and create new ones. There was a certain advantage at the time. Since Cuvier’s time an immense quantity of new discoveries had accumulated for the construction of a system of living things. Müller, Siebold, Leuckart, Vogt, and many others, had done a great deal of preparatory work. All this was of great assistance to the man who now came forward with courage and a talent for organisation. Nevertheless it needed real genius, together with almost boundless knowledge, to accomplish the task. We must remember how reactionary (even apart from the question of evolution) was the systematic work of distinguished and assuredly learned zoologists like Giebel at that time; they worked on in a humdrum way as if the more advanced students did not exist. How different it has all become since Haeckel’s thorough reform of classification! We are astounded to-day at the skill with which he drew lines in his very first sketch that were so near to the permanent truth. I need only point to the new scheme of the classification of the vertebrates. A good deal of his work was, of course, bound to be defective, because the facts were not yet known; for instance, in fixing the point at which the vertebrates may have evolved from the invertebrates. It was not until a year later that the discovery of the embryonic development of the ascidia by Kowalewsky threw light on this. Again, there was the solution of the problem of the ultimate root-connection of the great parallel animal stems. In this matter Haeckel himself brought illumination by his gastræa-theory.
On the whole this systematic introduction to the second volume would have sufficed of itself to secure for Haeckel a prominent position in the history of zoology and botany. He himself was chiefly proud of the fact that it was the first natural-philosophical system on the new lines to meet the rigorous demands of academic science, and indeed to revolutionise academic science. This enhances his complete triumph in the last two books of the volume. First man is introduced, with absolute clearness and decisiveness, into the system of evolved natural beings, as crown of the animal world, but subject to the same laws as the animal: a vertebrate, a mammal, whose nearest relatives are the anthropoid apes. Thus at last the “system of nature” was complete. It embodied the unity of nature. It formed the framework of facts for a unified natural philosophy, Monism. The monon, the “one,” embracing all things, that included nature in itself and itself in nature, became the last scientific definition of what people called “God.”
Thus the volume, which had begun the system of nature with the monera, closes with a chapter on the Monistic God—“the God in nature.” The conception of God in human fashion is rejected. Man is merely a vertebrate, a mammal, adapted in his whole structure to our little planet. A supreme Being to whom we ascribe omnipresence could not possibly be confined within the narrow limits of this vertebrate and mammal organisation. When we try to do so we fall into unshapely conceptions that are wholly unworthy of the most exalted of all words, ideas, and beings. It is in this connection that Haeckel uses for the first time the phrase “gaseous vertebrate,” that has so often been quoted and attacked since. He means to say that we are driven to such debasing and senseless definitions if we do not recognise in God the essence of the whole system of things; if we form our idea of him arbitrarily on any particular property of things within the system. We must beware—as he expressly says—of such confused and unworthy comparisons.
“Our philosophy,” Haeckel continues, “knows only one God, and this Almighty God dominates the whole of nature without exception. We see his activity in all phenomena without exception. The whole of the inorganic world is subject to him just as much as the organic. If a body falls fifteen feet in the first second in empty space, if three atoms of oxygen unite with one atom of sulphur to form sulphuric acid, if the angle that is formed by the contiguous surfaces of a column of rock-crystal is always 120 degrees, these phenomena are just as truly the direct action of God as the flowering of the plant, the movement of the animal, or the thought of man. We all exist ‘by the grace of God,’ the stone as well as the water, the radiolarian as well as the pine, the gorilla as well as the Emperor of China. No other conception of God except this that sees his spirit and force in all natural phenomena is worthy of his all-enfolding greatness; only when we trace all forces and all movements, all the forms and properties of matter, to God, as the sustainer of all things, do we reach the human idea and reverence for him that really corresponds to his infinite greatness. In him we live, and move, and have our being. Thus does natural philosophy become a theology. The cult of nature passes into that service of God of which Goethe says: ‘Assuredly there is no nobler reverence for God than that springs up in our heart from conversation with nature.’ God is almighty: he is the sole sustainer and cause of all things. In other words, God is the universal law of causality. God is absolutely perfect; he cannot act in any other than a perfectly good manner; he cannot therefore act arbitrarily or freely—God is necessity. God is the sum of all force, and therefore of all matter. Every conception of God that separates him from matter, and opposes to him a sum of forces that are not of a divine nature, leads to amphitheism (or ditheism) and on to polytheism. In showing the unity of the whole of nature, Monism points out that only one God exists, and that this God reveals himself in all the phenomena of nature. In grounding all the phenomena of organic or inorganic nature on the universal law of causality, and exhibiting them as the outcome of ‘efficient causes,’ Monism proves that God is the necessary cause of all things and the law itself. In recognising none but divine forces in nature, in proclaiming all natural laws to be divine, Monism rises to the greatest and most lofty conception of which man, the most perfect of all things, is capable, the conception of the unity of God and nature.”