fact. From all observations, it seems to be evident that those agencies which originated the species in general have ceased since man appeared. Now this fact is inconvenient for all those who, on metaphysical grounds, reject aim and purpose in the world and accept an aimless motion in the universe, a circle in which only identical powers are ever active to all eternity. From this standpoint, the scientists cannot, except by very artificial hypotheses, escape the conclusion that, if new species once originated through descent, new species ought still to originate through descent. In like manner, it is true, they are also obliged to accept the other conclusion: that if new species once originated through primitive generation, new species ought still to originate through primitive generation. On the other hand, those scientists who recognize aims in the world for which the world and each part of it is destined, and which are attained in the world through the processes of coming into existence, have to expect in advance that the organic kingdoms are also planned with reference to those aims. They naturally see the aim of the origin of species attained, where in the organic world beings appear who combine with the highest physical organization a self-conscious and responsible spiritual life, and who are capable of conceiving the ideal, even the idea of God. For, with the appearance of these beings, there enter upon the theatre of the world beings who go beyond the value of a purely physical organism and of a purely somato-psychical life, and in like manner represent again a higher order of beings; just as the first appearance of organic life on earth once introduced a new and higher stage of
existence in contrast to the inorganic world. Scientists who take this standpoint can readily adopt the fact that we do not now observe the origination of new species; for it is in full harmony with their metaphysical doctrines, without the same being on that account essentially dependent upon the confirmation or rejection of the hypothesis of the present constancy of species. With this very fact, the maxim that if new species once originated through descent, new species must still originate through descent, has lost for them its truth, and therefore its power of demonstration. So we see even here, while in the midst of the discussion of a purely scientific problem, in what close correlation metaphysics and natural science stand, and moreover—since the metaphysical view is most closely connected with the religious—in what close relationship religion and natural science stand. At the same time we also see how little the metaphysical interest, and much more how little the religious interest, has reason to avoid the investigation of facts in nature.
§ 4. The Theory of Evolution—Archæology, Ethnography, Philology.
The evolution theory teaches that the species have developed themselves one from another in gradual transitions, each of which was as small as the individual differences still observed to-day among the individuals of the same species. It is not without support, especially in the history of the development of plants and animals.
Each organic being becomes what it is by means of organic development. Each plant, even the highest organized, begins in its seed-germ with a simple cell,
and is differentiated in constant development up to the fully perfected individual. Each animal, even the most highly organized (man included), begins the course of its existence as an egg; and each egg has no greater value of form than that of a single cell. This egg-cell is differentiated, after fecundation, in gradual and imperceptible transitions, farther and farther, higher and higher, until the individual has reached its perfect organization. No organ, no function of the body, no power or function of the soul or of the mind, appears suddenly, but all in gradual development. Since we see all individuals thus originating by means of gradual development, the possibility lies very near that the different organic formations of all the organic kingdoms could also have been originated by the same means.
In still another direction does the history of the development of single plants and animals make this possibility plausible to us. In the animal world, and partly also in the plant world, the single individuals of higher species in their embryonic development pass through states of development, in the former stages of which not only the individuals of the most different species look confusingly similar to one another, but also the embryos in their organization remind us of the perfected state of much lower classes of beings. In order to give a clear idea of the first mentioned facts, Häckel, for instance, in his "Natural History of Creation" and in his "Anthropogeny," represents by engravings the embryos of different vertebrates and also of man; representations which—although, according to the judgment of competent scientists, unfortunately not exact, but modified, after the manner of stencil plates, in favor of
greater similarity—yet make it quite clear that the similarity of the different embryos must be very great. We see, for instance, on one table the embryos of a fish, a salamander, a turtle, a fowl; on a second, those of a pig, an ox, a rabbit, a man; on a third, those of a turtle, a fowl, a man; and we find the similarity really great. Examples of the second fact—that individuals of higher classes or orders in former states of their embryonic development represent an organization which corresponds to the full-grown individuals of the lower classes—are: the tail of the human embryo, the gill-arches of the embryos of reptilia, of birds, of mammalia, and of man. Now Häckel here takes up again an idea first suggested by Fritz Müller, and derives from these observations the "biogenetic maxim," as he calls it: "The history of the germ is an epitome of the history of the descent; or, in other words, ontogeny (the history of the germs or the individuals) is a recapitulation of phylogeny (the history of the tribe); or, somewhat more explicitly: that the series of forms through which the individual organism passes during its progress from the egg-cell to its fully developed state, is a brief, compressed reproduction of the long series of forms through which the animal ancestors of that organism (or the ancestral forms of its species) have passed from the earliest periods of so-called organic creation down to the present time." In his latest publication, "Ziele und Wege der heutigen Entwicklungsgeschichte," ("Aims and Methods of the Present History of Evolution"), he admits into the formulation of his biogenetic maxim also the consideration of those phenomena in the ontogenetic development which are no recapitulation of the history
of the stem, but originated by adapting the embryo to its surroundings. In the description and explanation of this theory, he uses a term which throws upon nature a peculiar reproach, never before made, namely: cenogeny, or history of falsifications, in contrast to palingeny, or history of abridgments. This amended formula now reads: The development of germs is an abridgment of the development of stems, and is the more complete according as the development of the abridgment is continued by inheritance, the less complete according as the development of the false is introduced by adaptation.
Now, we ask: Is this biogenetic maxim correct? and moreover, from the fact of the organic individuals originating through development, are we entitled to draw the conclusion that even the species must have originated through development? To this question we can no longer get an answer from the life-processes of living organisms; for we have already mentioned the fact that, according to the present state of our knowledge, we can no longer observe the origination of a new species. Moreover, the embryonic states of development show also, in all their similarity, even in the very first stages, and with especial distinctness in these first stages, many differences between the single species; and this is true especially of those species which, according to the followers of this so-called biogenetic maxim, should lie in the same stem-line,—so that the direct scientific value of the embryological results to the palæontological investigation, or of the latter to the former, is so far very slight. Such a problem, however, as the one contained in that biogenetic maxim, which only gives to investigators the direction in which possibly an