to his works a great charm. But on the other hand we dare not conceal that, even on the ground of explanations belonging purely to natural history, the character of hypothesis is often lost in that of arbitrariness and of the undemonstrable. Even the unlearned in natural science often enough get this impression when reading his works, and will find it confirmed by scientists who not only contradict his assertions in many cases, but disclose plain errors in his drawings-errors, indeed, exclusively in favor of the unity-hypothesis; and in other cases they show that drawings which are given as pictures of the real, represent merely hypothetical opinions. There is especially evident in his works an extremely strong tendency to impress on his hypotheses the character of an established and proved fact, by giving them the alluring name of laws. Entire systems of laws of the selection theory are produced, and all imaginable assertions are also immediately called laws. For example, Huxley, in his anatomical investigations of apes and men, arrives at the conclusion that the differences between the highest and the lowest apes are greater than the differences between the highest apes and man. This purely anatomical comparison, Häckel calls repeatedly "Huxley's Law." We are well aware that the idea of law is capable of great extension in meaning and in that respect we can refer to nothing more instructive than the well-meditated inquiry upon this idea in the "Reign of Law" of the Duke of Argyll (London, Strahan & Co.). But if we may venture to call purely anatomical comparisons of this nature laws, such a use of language destroys all logical reasoning; and this mistake appears again in Häckel's philosophic discus

We

sions, of which we shall have to speak hereafter. shall have to refer also hereafter to an additional embellishment, which Häckel thinks himself obliged to give to his works—namely, that he makes on every occasion the strongest attacks upon faith in a personal God, a Creator and Lord of the world; that he traces all the motives of human action to self-interest; that he denies the liberty of man and the moral system of the world ; that he makes consent to his view of things the criterion of the intellectual development of a man; and that he thinks to render a service to civilization by such a view of the world and of ethics.

In the consequent carrying out of the selection principle as the satisfactory key in explaining the origin of all species and also of man, Häckel is indeed, in spite of the approval of his works by the British master, more Darwinian than Darwin himself, who expressly refuses to give exclusive value to this theory of explanation. Hence there are among scientists only a few who go with him to this extent. In Germany, aside from the materialists, we only know of Seidlitz and Oskar Schmidt-who in the thirteenth volume of the "International Scientific Series" treats of "The Theory of Descent and Darwinism," and advocates not only the autocracy of the selection theory, but also all the monistic and atheistic consequences which are deduced from it. Perhaps Gustav Jäger, Schleiden, Bernhard Cotta -at least judging from their earlier publications-should be mentioned as followers of the pure selection theory; although they do not all draw from it the before-mentioned philosophic consequences. On the other hand, the number of those is very great who, although inspired

by Darwin to adopt the idea of an origin of species through descent and evolution, yet have more or less modified, laid aside, or entirely refused the very doctrine.which is especially new in Darwin's theory — the selection theory. In the following section we shall briefly give an account of them.

§ 3. Modifications of the Theory-Moriz Wagner. Wigand.

One of the most prominent objections to the selection theory, which strikes us at once from the standpoint of natural history, is the following: The varieties of a domesticated species, obtained by artificial breeding, are lost, and return to the original wild form of the species as soon as they are crossed long enough with other varieties or are left to themselves and to the crossing with individuals of the original form of their species; and hence we can not see how individual characteristics, even if favorable to the individual, will not be lost again by the crossing which is inevitable in a state of nature, with such individuals as do not possess those characteristics. Besides, it is an established fact, confirmed by all our observations stretching over thousands of years, that the characteristics of species are preserved in spite of all individual modifications, and that this preservation of the characteristics of species has its cause essentially in the free crossing of individuals.

This objection induced Moriz Wagner to take up again an idea already expressed by Leopold von Buch, and to complete the principle of a selection through natural breeding by another, and partly, indeed, to supplant it by the principle of isolation by migration. Isolated individuals, who, from any reason naturally to

be accounted for, leave the mass of their fellows, can from the very consequence of this isolation transmit to their offspring common individual characteristics which are not destroyed again by the crossing with other individuals. They will especially fix and transmit these individual characteristics, when they are favorable to them for the conditions of existence in their new place of living, and these individual characteristics will so much the more be increased and developed in a direction favorable to the subsistence of the individuals in their new place of living, as there are more closely connected with this isolation variations in the conditions of existence, in climate, geographical surroundings, food, and so on. He very attractively applies this theory also to the explanation of the origin of man. According to his opinion, even the nearest animal progenitors of man were isolated, and the isolating power was the rise of the great mountains of the Old World, which took place previous to the glacial period. One pair, or perhaps a few pairs, of those progenitors were driven away from the luxurious climate of the torrid zone to the northern half of the globe, and found their return cut off by glaciers and high mountains; in place of a comfortable life on the trees, necessity urged them to gain support from conditions less favorable to 'existence, and necessity, this mother of so many virtues and achievements, finally made man what he is. In following out these ideas, Moriz Wagner has gradually and more and more decidedly given up the selection theory, and opposed it by sharp criticisms.

This migration or isolation theory also found a degree of favor, but subordinate in its nature. For it

can not and will not pretend to solve the main problems. It only tries to explain how the individual variations, already in existence, might have been preserved and perhaps increased, and how new conditions of existence could have roused latent powers; but, not how these variations and these powers originated. Just as little is the selection theory able to explain this; but it pretends to do it, and hence we can easily comprehend how during the last few years a constantly increasing number of voices, and more important ones, have been raised against the selection theory. This opposition came not only from those who like Agassiz, Barrande, Emil Blanchard, Escher von der Linth, Göppert, Giebel, Sir Roderick Murchison, Pfaff, and others—directly reject each and every idea of descent on account of the difficulty in defending the selection theory; or who-like Karl Ernst von Baer,* (the

*It was only when the manuscript of this work was nearly finished and the first part of it had gone to the press, that the author received the second part of K. E. von Baer's "Studien aus dem Gebiete der Naturwissenschaften" (Studies in the Realm of Natural Sciences). It contains another essay on teleology, "Ueber Zielstrebigkeit in den organischen Körpern insbesondere," and a treatise on Darwin's doctrine, "Ueber Darwin's Lehre," which Baer had promised long ago and which the public had anxiously awaited. It is no little satisfaction to find that I, from my modest premises, reached results regarding the naturo-philosophical problems and their weight in the religious realm which so fully harmonize with the views of this first authority in the realm of the history of development. I shall still have occasion here and there to avail myself of a study of this latest and most important publication upon the question of Darwinism, and shall confine myself here to the remark that von Baer, although he rejects the selection theory and the superficial treatment of the principle of evolution on the part of materialists, is by no means disinclined to the idea of the origin of species through descent, whether in grad