The living and what is called the “dead” must be compared. Linné’s three rigid kingdoms—animal, plant, and mineral—needed definitions in harmony with the new ideas. Haeckel himself had discovered the “monera,” the living particles of plasm that did not seem to have reached the stage of the true cell. Here, clearly, was the lowest level of the living. At the same time we reach the most complex specimen of the inorganic from the morphological point of view—that is to say, the most interesting in its individual form—the crystal. The differences begin to give way. What marvellously similar functions! From the dead mother-water is built up, purely by chemico-physical laws, the beautiful structure of the crystal. From the lowest living particle of plasm without any special organs, as we see in the radiolaria, are formed the beautiful siliceous frames that Haeckel had collected in such quantities at Messina. Is it more than a hair’s breadth to pass from one to the other? The deeper we go in the study of living things, the slighter become the differences that separate them from “dead matter.” On the other hand, the higher we go in the structure of crystals, the more striking is the resemblance to the living thing. Two chains of thought seem to be started. What we call “dead” is really alive: what we call living is really subject to the same laws as the “dead.” The solution is found in complete Monism. Living and dead are not antithetic. Nature is one; though we see it in different stages of development. We call one of them the crystal, another the cell, or the moneron, or the protozoon; another the plant, another the animal. Historically it all hangs together. The same laws hold sway throughout. In framing my arbitrary definitions I can say either that the dead is living, or that the living does not differ essentially from the dead. In the chain of living things man comes from the primitive cell, the moneron. This in its turn has developed from something earlier—“naturally” developed. The very idea of life forces us to seek the predecessors of the monera. Hence we speak of “spontaneous generation,” as what was dead according to our ordinary use of language has begun to live. In point of fact it is merely development of a unified whole. There is no gap, no leap, no act that is not natural. The dead and the living never were really antithetic.
The insistent statement that not only does the living approach the inorganic, but the inorganic approaches the living, is quite “Haeckelian.” The study of the “life” of crystals is one of the best parts of the book. Later generations will appreciate it. We are much too narrow to-day when we merely reflect that life, even the life of man, can be traced by evolution down to what we call dead matter. We forget that this “matter” is already high, since it potentially contains life, and even man, the crown of life. Many people imagine that the derivation of man from “dead matter” is equal to turning a king into a beggar. They do not reflect that, on the other hand, a beggar is turned into a king. When I say that life arose one day out of the inorganic, or that a crystal was turned into a cell, my statement really involves the complementary truth that the inorganic potentially contains life in itself. Otherwise we have the old miracle over again of something being produced out of nothing, in spite of our spontaneous generation. Haeckel has always been clear on this point. His later studies of the soul of the atom and the plastidule only carry out the absolutely logical treatment of the question that we find in these chapters of the first volume of the Morphology.
Incidentally the question is raised whether the plant or the animal was evolved first. Animal and plant are, of course, not rigidly distinct from each other. They are only the two great branches of the Darwinian evolution of living forms, and are united at the bottom, however much they diverge above. Gegenbaur had represented this years before (1860) in a figure that Haeckel quotes in his Monograph on the Radiolaria in 1862. The whole kingdom of living things must be conceived “as a connected series, within which we find two lines diverging from a common centre and representing a gradual differentiation and development of organisation.” The terminal points of these lines (the highest plant and the highest animal) are very different from each other, but the difference gradually disappears as we go back towards the common centre, and the lowest stages in each kingdom can hardly be distinguished from each other. For these lowest stages Haeckel now carries out a plan that very quickly forced itself on him.
He forms them into a new kingdom of life. To the animal and plant kingdoms he adds the primitive realm of the beings that showed unequivocal signs of the possession of life, yet were neither animals nor plants. He gives them the name of “Protists.” To botany and zoology is now added protistology.
The name “protists” (from protiston, the very first) is familiar to every one in biology to-day. If protistology has not yet been securely established as a special branch of science, that is due to the circumstance that a strict limit cannot be determined on either the plant or the animal side, so that the botanist encroaches on the province at one point and the zoologist at another. But when we remember that Haeckel’s protists include the well-known bacilli, on which whole libraries are accumulating to-day, it is clear that the province must be definitely marked off at some date in the near future, whether one accepts Darwinism or no.
These important innovations in technical biology show very clearly how sound and fruitful the new “natural philosophy” was. We have to go back to the untenable and utterly impracticable systems of Hegel, Schelling, and Steffen, which were immediately rejected as the trifling of dilettanti, or even to much that the admirable Oken did on the scientific side, if we would measure the whole distance between what people understood in the sixties by “natural philosophy” and the real reformed philosophy that Haeckel gave to the world. This becomes clearer at every step we take in his work.
The first book has determined the method that leads to morphology, the science of forms. The second has ranged the organic forms—protists, plants, and animals—over against the inorganic or “dead” forms, as far as this is possible from the new evolutionary point of view. We feel that the third book will pass on to Darwin, and explain the world of organic forms by the Darwinian laws of evolution. Then the programme would be carried out in its main features.
But Haeckel writes two whole books before he comes to this, and they are, perhaps, the most characteristic in the work. He only “adopted” the theory of evolution in the sense that he applied it far more thoroughly than Darwin to practical problems. In these two books he is entirely himself. They are, at the same time, the most difficult in the work. Even to-day they place him on a lofty and lonely height apart from the great and strenuous controversy over Darwinism. I believe that the time will yet come that will fully appreciate these books. Through them Haeckel will play a part in philosophy of which we have at present no prevision.
There is a word that is inseparable from the word “form”—individuality. Morphology, which does not analyse, but studies the form-unities as a whole in the sense of Goethe’s definition, comes from the nature of things to deal with the individual. In our artistic illustration the Venus of Milo, as a form-unity, is an æsthetic individuality. When its form is destroyed, its individuality perishes.
Let us apply this to any one of the higher plants or animals. Take a turtle, for instance. A definite individual embodies the definite form to which I give the name. This form as such is entirely lost if I cut up the turtle until it is unrecognisable. The limit of morphological study seems to be, just as in the case of the Venus of Milo, the integrity of the individual turtle. Yet in the living turtle we find an enormous difference.