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RISE OF THE DARWINIAN THEORIES.

§ 1. Direct Predecessors.—Lamarck.

The first man who gave direct expression to the idea of a successive generation of the species through transmutation, and who attempted to follow it up in a scientific way, was the French naturalist and philosopher, Jean Lamarck, born 1744. In the year 1801, and subsequently, he published his views, first in smaller essays and afterward more in detail in his "Philosophie Zoologique," which appeared in 1809, and in the first volume of his "Histoire Naturelle des Animaux sans Vertèbres," published in 1815. In these works Lamarck upholds fully the descent and evolution theory, and maintains that the simplest organisms are generated through a generatio spontanea, which is still taking place; but that all the more developed organisms, including man, are descended through a gradual change from other species. With this theory, he put himself in direct and conscious opposition to the old doctrine of the immutability of species and their characteristics, which had been ably maintained by Linnæus, and also made some attempts at explanation which approach very nearly the selection theory. A change in the physical conditions of life, especially the force of habit in the use or disuse of the organs, the inheritance of physical and psychical qualities thus attained, and the extension of the process of transmutation into extraordinarily long periods of time with very slight changes, are also, in his view, the probable causes of the variation and development of the species. He only lacks the idea of a natural selection in the struggle for existence, and the comparison of the processes in nature with the methodical selection of man in the breeding of domestic animals and plants, to identify his views with those of Darwin.

At first, Lamarck met only with violent opposition; but after a little while his views ceased to attract attention. The time had not yet come to make such an attempt at observing nature from the standpoint of evolution. The sciences which favor such a mode of observation, and even demand it—such as comparative anatomy and physiology and the history of the development of the different plants and animals—were only in their infancy, or were—like palæontology and the comparative geography of plants and animals—not yet in existence. The influence of Linnæus, whose views diametrically opposed those of Lamarck, predominated over all the investigations of natural science; Buffon, who favored the ideas of Lamarck, and loved to trace a unity in natural phenomena, was too instable in his investigations and views to arrive at a comprehensive principle; and even the eminent naturalist, Cuvier, of Montpellier, showed in his observation of nature a predilection for analysis rather than synthesis, and although his comprehensive mind inclined to generalize and explain, he placed himself in decided opposition to a theory which was founded only on a few decisive facts.

This last mentioned deficiency seems to have been the main cause of Lamarck's views soon being lost sight of. They nowhere found a support in facts; the force of habit played in them an exaggerated and unnatural rôle; the different illustrations of them—such as the long neck of the giraffe explained by the permanent and inherited habit of browsing on the branches of high trees, or the web on the toes of frogs, swimming-birds, etc., explained by the habit of swimming—were talked about and laughed at more as curiosities than as worthy of serious consideration.

Only twice after this did the question put by Lamarck attract wider attention from the learned world. The first time was when, in 1830, the bitter contest arose at the Academy of Paris, between Cuvier and Etienne Geoffrey St. Hilaire, the father of Isidor G. St. Hilaire. Geoffrey St. Hilaire had views similar to Lamarck's, but reached them from quite a different standpoint—from the observation of the analogy and homology of the organs; and accounted for the variation of species, not by the use or disuse of the organs, but on the one hand by the common original type of the organs, and on the other by the varied influence of the surroundings—the monde ambiant. Lamarck himself seems not to have been mentioned in this contest. The controversy turned much more on the question whether in observing nature we can proceed by synthesis and find in the analogies of the organisms the principles for explaining the real connection between the different organic forms, or whether the analytical process is the only correct one, and the synthetical should be discarded. The solution of it will probably be, that the one process must be supplemented by the other, as Goethe has already shown in his account of this controversy; but at that time it was decided in favor of the analytical principle, and the question was for the time dropped. It came up for a second time, but created little excitement, in 1844, when an anonymous work, "Vestiges of the Natural History of Creation," directed the attention and the interest of scientists again to Lamarck and his doctrine. But this interest also soon came to an end, until through Darwin's first publication the half-forgotten man again suddenly attained great honor.

Those who wish to form a closer acquaintance with the different advocates of the evolution theory before Darwin's appearance, will find them carefully arranged in the historical sketch which Darwin gives in the introduction to his work on "The Origin of Species"; and the most important extracts of Lamarck's "Philosophie Zoologique" are to be found in Oscar Schmidt's "Descent and Darwinism."^[1]

§ 2. Indirect Preparations.

While thus the ideas of Lamarck gradually fell into partial oblivion, yet contemporaneous with and following them arose several other series of thoughts, views, and investigations, which, although they only indirectly prepared for the revival of the evolution theory, yet exercised a deeper and more lasting influence on the minds of scientists. We refer to the ideas in regard to natural phenomena held during the first decades of our century; further, to the principles of comparative anatomy which, up to the present time, partly dependent and partly independent of natural philosophy, have been expressed, valued, and admired as leading thoughts; and, lastly, to the empiric results of comparative anatomical and biological investigations in palæontology and geology, as attained by the help of those very principles. And even physics and astronomy had to coöperate in preparing the way for the idea of evolution.

The philosophical ideas referred to, together with the points of view and results of comparative anatomy, led more and more decisively to the idea of an original form, or type, which retains its identity in all the modifications of form in plants and animals; and of a ground-plan, which is realized in the systems of the plant and animal world in higher and higher differentiations and in more and more developed modifications, diverging farther and farther from the prototype until it reaches its highest form, still reducible to the prototypes, in the most highly organized dicotyledons in plants, and in the animal world in the mammalia, and lastly in man.

Men like Cuvier and Geoffrey St. Hilaire, who otherwise stand diametrically opposed to each other, unite in these and kindred ideas. The naturalist Oken attains the same result, tinged with the views of Schelling; the poet Goethe, from an intuitive knowledge of nature, arrived at the same conclusion. The former, during a journey in the Hartz Mountains, at the sight of a bleached deer's skull, and the latter, upon picking up a sheep's skull in the Jewish cemetery at Venice, were struck by the same thought: the skull is only a modified vertebra. Oken founded upon this idea and kindred analogies his profound philosophy of the system of animals and plants which comes very near to the evolution theory, and in his cosmogony traces all organisms to a protoplasm in such a way as to bring him in this respect also very near to Darwinism. Goethe, in his metamorphosis of plants, develops ideas in which, in all seriousness, he makes a concrete application of his thought of a prototype to the leaf of a plant; and proved for zoölogy the fruitfulness of his idea of a type by his well known discovery of the mid-jaw bone in man. Although Oscar Schmidt seems to be decidedly right in supposing, in opposition to Ernst Häckel, that Goethe did not intend to have his idea of unity and development taken in a real but in an ideal sense, and hence could not be called a direct representative of the evolution theory, still he is all the more decidedly a predecessor of that theory in directing attention to the unity in plan and metamorphosis of plants and animals. Louis Agassiz, who, on the other hand, continued up to his death in opposition to the entire doctrine of descent, made the idea of types the principle of his whole classification, and said: "Man is the purpose toward which the whole animal creation tends from the first appearance of the first paleozoic fish." Richard Owen, who rejected the selection theory and favored that of descent, published, long before Darwin's appearance, some most interesting results of his anatomical and palæontological investigations from the point of view of the prototype and its modifications. "Man, from the beginning of organisms, was ideally present upon the earth," is a sentence which we quote from Owen's works.

In short, this ideal momentum in the observation of the organic kingdoms is not only the most beautiful blossom and the ripest fruit of the union between laborious and comprehensive detailed investigations and a generalizing philosophic penetration, but it was also a very efficient preparation of the mind for the evolution problem, so far as the summing up of the organisms under a type and plan is only the ideal reverse of its realistic reduction to a common pedigree.

We have yet to add the investigations in regard to the history of evolution of the single organisms, as well as those in comparative anatomy, which in former centuries were begun by scientists like Swammerdam and Boerhave and carried more nearly to completion by K. E. von Baer, Carus, and others. In reducing all the tissues of plants and animals to one cell, and tracing back also their individual developments to the first differentiation of the simplest cell, they followed out the unity of the plan of the organic kingdoms—which hitherto had been maintained only ideally and proclaimed as a philosophic postulate—farther and deeper into the sphere of empiric reality. We must mention, moreover, the great palæontological discoveries which, from the first foraminifera of the Cambrian formations up to the historical period of man, showed a great progressive scale in the appearance of the organisms and a very wide relationship between this scale and the natural systems of botany and zoölogy; and, finally, the principles of geology, which, under the leadership of Sir Charles Lyell, starting from the idea of an identity of the powers which were active in former times with those of the present, attempted to explain the most violent of the changes in the earth's crust in former times by causes active to-day. This often explains prodigious effects—such as the elevation and settling of entire mountains and continents—by the constant and related action of the slightest causes and most gradual steps; it opens the perspective into vast epochs of long and numerous geological periods; and sometimes, where scientists like Cuvier and Agassiz have supposed the most complete cataclysms and the most universal revolutions of the globe, there prove to have been only gradual changes with revolutions very partially and locally limited.

Finally, if we take into consideration the grand discoveries which strikingly illustrate the connection in extent and quality between the universe and all its agencies and powers—such as Robert von Mayer's discovery of the conservation of force and of the mechanical equivalent of heat, or the spectrum analysis and the information which it gives us by ever-increasing evidences of the identity of the cosmic and telluric substances—we may venture to say that the scientific and intellectual ground was well prepared for a theory which takes the origin of organisms into this common relationship of the essential unity and development of the universe.

Only one thing more remained to complete the hypothesis offered by Lamarck, of the fact of a development of species by a new and more satisfactory answer to the question as to the manner of their development. The task of answering in a more comprehensive and scientific way the question as to the manner of development has been undertaken by Darwin in his selection theory. Alfred Russell Wallace, who arrived at the same results contemporaneously with and independently of Darwin, has, with praiseworthy modesty, renounced his claim to priority of the discovery, as Darwin had been longer engaged in working out his theories and had begun to collect materials for proof.