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Updated: June 12, 2025
Eimer, on the other hand, is sharply antagonistic, especially to Weismann; he takes his proofs from the animal kingdom, and in the second volume of his large work already mentioned, which deals with the “orthogenesis of butterflies,” he attempts to set against the Darwinism “chance theory,” a proof of “definitely directed evolution,” and therefore of the “insufficiency of natural selection in the formation of species.”
Eimer’s Orthogenesis. Organisation is due to internal causes. Structural characters crystallise out, as it were. “Orthogenesis,” or the definitely determined tendency of evolution to advance in a few directions, is a law for the whole of the animate world.
They completely passed out of existence, leaving behind them only very much smaller reptiles. Eimer, of Germany, has based on facts like these his theory of Orthogenesis. He says that variations in animals are not indefinite and in every direction, but that they follow along clear and definite lines.
On this basis Weismann attempts to reach explanations of the phenomena of variation, of many apparently Lamarckian phenomena, and of recognised cases of “orthogenesis,” and seeks to complete and deepen Roux’s theory of the “struggle of parts,” which was just another attempt to carry Darwinism within the organism.
A combination of Lamarckian and Darwinian factors has been proposed by Osborn, Baldwin, and Lloyd Morgan, in the theory of organic selection. The theory of orthogenesis propounded by Naegeli and Eimer, now gaining much ground, holds that evolution takes place in direct lines of progressive modification, and is not the result of apparent chance.
The same statement can be made of all the many, many other known factors in development, from fecundity to concealing coloration; and behind them lie forces as to which we veil our ignorance by the use of high-sounding nomenclature as when we use such a convenient but far from satisfactory term as orthogenesis.
There are dozens of theories, mutation, orthogenesis, Weismanism, Mendelianism, etc., and each has its adherents, but they agree in one thing, that "Natural Selection" does not account for the forms of life on earth to-day. The revolt against "Natural Selection" came some forty years ago. It was announced in two famous declarations by Spencer and Huxley.
Another circumstance seems to us to have been entirely overlooked, and it is one which gives the theory of selection an inevitable appearance of truth, even if it is essentially false, and thus makes it very difficult to refute. Assuming that the recognition of teleological factors is valid, that there is an inward law of development, that “Moses” or whoever one will was undoubtedly right, it is self-evident that, because of the indubitable over-production of organisms, there would even then be a struggle for existence on an immense scale, and that it would have a far-reaching “selective” influence, because of the relative plasticity of many forms of life. Beyond doubt it would, in the course of æons, have applied its shears to many forms of life, and probably there would be no organisms, organs, or associations in the evolution of the ultimate form of which it had not energetically co-operated. Its influence would, perhaps, be omnipresent, yet it might be far from being the all-sufficient factor in evolution; indeed, as far as the actual impulse of evolution is concerned, it might be a mere accessory. Unless we are to think of the forms of life as wholly passive and wooden, the struggle for existence must necessarily be operative, and the magnitude of its results, and their striking and often bizarre outcome, will tend ever anew to conceal the fact that the struggle is after all only an inevitable accompaniment of evolution. And thus we understand how it is that interpretations from the point of view of an inward law of development, of orthogenesis, or of teleology, notwithstanding their inherent validity, have
The second part of Eimer's work dealing with the origin of species, which appeared after an interval of ten years, bears the title: "Orthogenesis of Butterflies." Leipzig, 1897. In this book substantially the same thoughts occupy the mind of the author as in the former volume, but in many respects they are more mature, and conspicuously more definite and precise.
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