For a certain proof that the conception of species rests on a subjective abstraction and has a merely relative value—like the conception of genus, family, order, class, &c.—no class of animals is of so much importance as that of the Sponges. In it the fluctuating forms vary with such unexampled indefiniteness and variability as to make all distinction of species quite illusory. Oscar Schmidt has already pointed this out in the siliceous sponges and keratose sponges; and I, in my monograph, in three volumes, on the Calcareous Sponges (the result of five years of most accurate investigations of this small animal group), have pointed out that we may at pleasure distinguish 3, or 21, or 111, or 289, or 591 different species. I also believe that I have thus convincingly demonstrated how all these different forms of the calcareous sponges may quite naturally, and without any forcing, be traced to a single common parent-form, the simple—and not hypothetical, but existing at this present day—the simple Olynthus. Hence I think I have here produced the most positive analytical evidence of the transformation of species, and of the unity of the derivation of all the species of a given group of animals, that is generally possible.
Properly, I might spare myself these disquisitions on the question of species, for Virchow does not go into this main question of the theory of descent—but this is very characteristic of his attitude. And just as he nowhere thoroughly discusses the doctrine of transformation, neither does he enter generally on the refutation of any of the other certain proofs of the doctrine of descent which we in fact possess at the present day. Neither the morphological nor the physiological arguments for the theory of descent, neither the rudimentary organs nor the embryonic forms, neither the paleontological nor the chronological argument are anywhere closely examined and tested as to their worth or their worthlessness as "certain proofs." On the contrary, Virchow takes them quite easily, sets them aside, and declares that "certain proofs" of the doctrine of descent do not exist, but remain to be discovered. To be sure, he does not indicate where they are to be sought, nor can he indicate it. How is this strange conduct to be explained? How is it possible that a distinguished naturalist should resist the most important step forward of modern natural science without in any way specially investigating it, without even practically testing and refuting the most weighty arguments in its favour? To this question there is but one answer. Virchow is not generally intimate with the modern doctrine of evolution, and does not possess that knowledge of natural science which is indispensable for any well-grounded judgment on it.
After collecting and carefully reading all that Virchow, during many years, had written against evolution, I arrived at the conviction that he had not thoroughly read either Darwin's great work on the Origin of Species, nor any other work on the theory of descent, nor had he thought the matter out with such attention as so serious and intricate a subject absolutely demands. Virchow did with these works as it has been his well-known custom to do with many others—he hastily turned over the pages, caught at a few leading words, and without any farther trouble he has discoursed upon them, and, which is worst of all, has perpetuated these discourses through the press.
To excuse this conduct, and to account for Virchow's enigmatical position in the battle of evolution, we must consider what changes this highly-gifted and meritorious man has gone through in the course of the last thirty years. The most important and fruitful part of his life and labours was indisputably during the eight years when he resided in Würzburg, from 1848 to 1856. There Virchow, with all the keenness of his youthful intellect, with a sacred enthusiasm for scientific truth, with indefatigable powers of work and the rarest insight, worked out that glorious reform of scientific medicine which will shine through all time as a star of the first magnitude in the history of medical science. In Würzburg, Virchow elaborated that comprehensive application of the cellular theory to pathology which culminates in the conception that the cell is an independent living elementary organism, and that our human organism, like that of all the higher animals, is merely a congeries of cells—a highly fertile conception, which Virchow now denies as resolutely as he then supported it. In Würzburg, twenty-five years since, I sat devoutly at his feet, and received from him with enthusiasm that clear and simple doctrine of the mechanics of all vital activity—a truly monistic doctrine, which Virchow now undoubtedly opposes where formerly he defended it. In Würzburg, finally, he wrote those incomparable critical and historical leading articles which are the ornament of the first ten yearly series of his "Archives" of pathological anatomy. All that Virchow effected as the great pioneer of reform in medicine, and by which he won imperishable honour in the scientific treatment of disease,—all this was either carried out or preconceived in Würzburg; and even the celebrated "Cellular Pathology," a course of lectures which he delivered during the first year and a half after quitting Würzburg for Berlin, consists only of the collected and matured fruits of which the blossoms are due to Würzburg.
In the autumn of 1856 Virchow left Würzburg to settle in Berlin. The exchange of a narrow sphere of labours for a wider one, of small means and appliances for greater ones, proved unfavourable in this case, as in many similar cases. Since he has been in Berlin, in a "great Institution," and with luxurious appliances, all the scientific results which Virchow has as yet brought to light are not to be compared, either as to quality or quantity, to the grand and immortal achievements which he himself effected in the little institute of Würzburg with the scantiest means—a new proof of the maxim enunciated by me, and hitherto never confuted, that "the scientific results of an institute are in inverse proportion to its size." (See "The Aim and Methods of Modern Evolution."[14])
Still more grave is the circumstance that, since settling in Berlin, Virchow has more and more exchanged his theoretical scientific activity for practical political life. It is well known how prominent a part he plays there in the Prussian Chamber of Representatives, how he raised himself to be the leader of the party of progress, and, to give this political position a broader basis, took part in the representation of the citizens of the capital; how he has taken a most active interest, as city commissioner, in all the petty anxieties and concerns which the charge of such a city as Berlin entails. I am far from blaming, as many have blamed, the political and civic activity to which Virchow has indefatigably devoted his best powers. If a man feels in himself the inclination and vocation with strength and talent enough, to play a conspicuous political part, by all means let him do so; but verily I do not envy him; for the satisfaction which is derived from the most successful and fruitful political activity is not, to my taste, to be compared with that pure and disinterested satisfaction of the mind which results from absorption in serious and difficult scientific labours. In the turmoil of the political and social struggle, even the most splendid civic crown will be dulled by the stifling dust of practical life, which never reaches the ethereal heights of pure science and never rests on the laurels of the thoughtful investigator. However, as I have said, that is a matter of taste. If Virchow really believes that he is doing a greater service to humanity by his practical political life in Berlin than he formerly did by his theoretical scientific work in Würzburg, that is his affair; but for all that, in his former sphere he was incomparable, and cannot be replaced; in the latter this is not the case.
If a distinguished man, be he never so remarkable for uncommon power of work and universal gifts, passes the whole day in the friction of political party-struggles, and throws himself as well into all the petty and wearisome details of daily civic life, it is impossible for him to maintain the requisite feeling for the progress of science—particularly when it advances so rapidly and incessantly as is the case in our day. It is therefore quite intelligible that Virchow should soon have lost this feeling, and in the course of the last two decades have become more and more estranged from science. And this estrangement has at last led to so complete a change in his fundamental views, to such a metapsychosis, that the present Virchow of 1878 is hardly in a position to understand the youthful Virchow of 1848.
We have seen a similar mental change occur contemporaneously in our greatest naturalist, Carl Ernst von Baer. This gifted and profound thinker and biologist, whose name marks a new epoch in the history of evolution, had in his later years become wholly incompetent even to understand those most important problems of his youthful labours which opened up new paths of inquiry. While in his early years he laid down principles of the greatest value to our modern doctrine of evolution, and even went very near to adopting this hypothesis into his system, at a later period he utterly denied it, and by his writings on Darwinism proved that he was no longer generally capable of mastering this difficult problem. As I am one of Von Baer's warmest admirers, and in my "Evolution of Man," as well as in the "History of Creation," and in other places, have most emphatically expressed that sincere esteem, I thought I might venture to forbear from calling attention to the discrepancy between the lucid, monistic principles of Von Baer in his youth, and the confused dualistic views of his old age. But as many opponents of Darwinism—and among them particularly the Old Catholic philosopher of Munich, Huber, who has written a series of articles in the "Augsburger Zeitung"—have made constant capital out of the harmless talk of the feeble old Von Baer, I must in this place explicitly declare that this dualistic prating of the old man is quite incapable of shaking the monistic principles of the young and enterprising pioneers of science, or of giving them the lie.
In his autobiography Von Baer gives us the explanation of this striking contradiction. In 1834 he entirely and for ever abandoned the province of the history of development, at which for twenty years he had laboured incessantly, and where he had earned splendid laurels. To escape from the haunting and importunate ideas of the science which had so wholly absorbed him, he fled from Königsberg to Petersburg, and subsequently busied himself in scientific inquiries of a quite different character. Twenty-five long years passed by, and when Darwin's work appeared in 1859, Von Baer had too long undergone a metapsychosis to be able to understand it. In Von Baer, as in Virchow, the course of this remarkable metapsychosis is highly instructive, and will itself afford to the thoughtful psychologist an interesting evidence of the doctrine of evolution.
However, the lack of comprehension of our modern evolution-hypothesis is easier to explain in Virchow's case than in Von Baer's, for this reason: morphological knowledge was greatly lacking to Virchow, while Von Baer possessed it in the highest degree. Now morphology is precisely that very department of inquiry in which our theory of descent has its deepest and strongest roots, and has matured the most glorious fruits of knowledge. The study of organic forms, or morphology, is thus, more than any other science, interested in the doctrine of descent, because through this doctrine it first obtained a practical knowledge of effective causes, and was able to raise itself from the humble rank of a descriptive study of forms to the high position of an analytical science of form. It is true that by the beginning of this century the most comprehensive branch of morphology—i.e., comparative anatomy—which was founded by Cuvier and splendidly developed by Johannes Müller, had laid the foundations on which to build a truly philosophical science of form. The enormous mass of various empirical material, which had been accumulated by descriptive systematists and by the dissections of zootomists since the time of Linnæus and Pallas, had already been abundantly matured and utilised in many ways for philosophic purposes by the synthetic principles of comparative anatomy. But even the most important universal laws of organisation—of which the old system of comparative anatomy was one—had to take refuge in mystical ideas of a plan of structure and of creative final causes (causæ finales); they were incapable of arriving at a true and clear perception of effective mechanical causes (causæ efficientes). This last, most difficult, and grandest problem, Charles Darwin was the first to solve in 1859, by setting Lamarck's theory of descent, which was already fifty years old, on a firm footing by his own theory of selection. By this hypothesis it was first made possible to fit together the rich materials which had been previously amassed, into the splendid edifice of the mechanical science of form. (See my "General Morphology," vol. i. chap. iv.)