CERTAIN PROOFS OF THE DOCTRINE OF DESCENT.
All the common phenomena of Morphology and Physiology, of Chorology
and Oekology, of Ontology and Paleontology, can be explained by the
theory of descent, and referred to simple mechanical causes. It is
precisely in this, viz., that the primary simple causes of all these
complex aggregates of phenomena are common to them all, and that other
mechanical causes for them are unthinkable--it is in this that, to us,
the guarantee of their certainty consists. For this reason all these
vast and manifold aggregates of facts are so many evidences of the
doctrine of descent. This fundamental relation of facts has been so
often expounded that I need dwell no farther on it in this place;
those who wish for any closer discussion of it are referred to my
"General Morphology" (vol. ii. chap. xix.), or "The History of
Creation,"[12] or "The Evolution of Man" (vol. i. p. 93).[13]
And where is yet farther proof of the truth of the theory of descent
to be found? Neither Virchow, nor any one of the clerical opponents
and the dualistic philosophers who are perpetually reiterating this
cry for more certain evidence, anywhere indicate where possibly such
evidence is to be sought. Where in all the world can we discover
"facts" which will speak more plainly or significantly for the truth
of transmutation than the facts of comparative morphology and
physiology; than the facts of the rudimentary organs and of embryonic
development; than the facts revealed by fossils and the geographical
distribution of organisms--in short, than the collective recognised
facts of the most diverse provinces of biological science?
But I am in error--the certain proof that Virchow demands in order to
be perfectly satisfied with the evidence, is to be supplied by
"experiment, the test as well as the highest means of evidence." This
demand, that the doctrine of descent should be grounded on experiment,
is so perverse and shows such ignorance of the very essence of our
theory, that though we have never been surprised at hearing it
continually repeated by ignorant laymen, from the lips of a Virchow it
has positively astounded us. What can in this case be proved by
experiment, and what can experiment prove?
"The variability of species, the transformation of species, the
transition of a species into one or more new varieties," is the
answer. Now, so far as these facts can be proved by experiment, they
actually have long since been experimentally proved in the completest
manner. For what are the numberless trials of artificial selection for
breeding purposes which men have practised for thousand of years in
breeding domestic animals and cultivated plants, but physiological
experiments which prove the transformation of species? As an example
we may refer to the different races of horses and pigeons. The swift
race-horse and the heavy pack-horse, the graceful carriage-horse and
the sturdy cart-horse, the huge dray-horse and the dwarfed pony--these
and many other "races" are so different from each other, that if we
had found them wild we should certainly have described them as quite
different varieties of one species, or even representatives of
different species. Undoubtedly, these so-called "races" and "sports"
of the horse tribe differ from each other in a much greater degree
than do the zebra, the quagga, the mountain horse, and the other wild
varieties of the horse, which every zoologist distinguishes as "bonae
species." And yet all these artificial varieties, which man has
designedly produced by selection, are descended from a single common
parent-form, from one wild "true variety." The same is the case with
the numerous and highly differing varieties of pigeons. Domestic
pigeons and carrier-pigeons, turbits and cropper-pigeons, fantail
pigeons and owls, tumblers and pouters, trumpeters and laughing
pigeons (or Indian doves), and the rest, are all, as Darwin has
convincingly proved, descendants of a single wild variety, the
rock-pigeon (_Columba livia_). And how wonderfully various they are,
not only in general form, size, and colouring, but in the particular
form of the skull, the beak, the feet, and so forth! They differ much
more in every respect each from the others than the numerous wild
varieties which, in systems of ornithology, are recognised as true
varieties, and even as true species. It is the same with the different
artificial varieties of apples, pears, pansies, dahlias, and so on; in
short, of almost all the domestic varieties of animals and plants. We
would lay particular stress on the fact that these artificial species
which man has produced or created by artificial breeding and through
experimental transformation out of one original species, differ far
more one from another in physiological as well as in morphological
conditions than the natural species in a wild state. With these it is
self-evident that any proof by experiment of a common origin is wholly
impossible. For, so soon as we subject any wild variety of animal or
plant to such an experiment, we bring it under the conditions of
artificial breeding.
That the morphological conception of a Species is not a positive but
only a relative conception, and that it has no other absolute or
positive value than those other similar system-categories--sports,
varieties, races, tribes, families, classes--is now acknowledged by
every systematiser who forms an honest and unprejudiced judgment of
the practical systematic distinction of species. From the very nature
of the case there are no limits to arbitrary discretion in this
department, and there are no two systematists who are at one in every
instance; this one separating forms as true varieties which that one
does not. (Compare on this point "History of Creation," vol. i., p.
273.) The conception of variety or species has a different value in
every small or large department of systematic Zoology and Botany.
But the conception of species has just as little any fixed
physiological value. In respect to this we must especially insist that
the question of hybrid offspring, the last corner of refuge of all the
defenders of the constancy of species, has at present lost all
significance as bearing on the conception of species. For we know now,
through numerous and reliable experiences and experiments, that two
different true varieties can frequently unite and produce fertile
hybrids (as the hare and rabbit, lion and tiger, many different kinds
of the carp and trout tribes, of willows, brambles, and others); and
in the second place, the fact is equally certain that descendants of
one and the same species which, according to the dogma of the old
schools, could always effect a fertile union under certain
circumstances, either cannot effect such a union or produce only
barren hybrids (the Porto-Santo rabbit, the different races of horses,
dogs, roses, hyacinths, &c.; see "History of Creation," vol. i., p.
146).
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 Wuerzburg, 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 Wuerzburg, 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 Wuerzburg, 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 Wuerzburg, 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 Wuerzburg;
and even the celebrated "Cellular Pathology," a course of lectures
which he delivered during the first year and a half after quitting
Wuerzburg for Berlin, consists only of the collected and matured fruits
of which the blossoms are due to Wuerzburg.
In the autumn of 1856 Virchow left Wuerzburg 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
Wuerzburg 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 Wuerzburg, 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 Koenigsberg 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 Mueller, 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 Linnaeus 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 (_causae finales_); they were
incapable of arriving at a true and clear perception of effective
mechanical causes (_causae 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.)
The immeasurable step which Darwin thus made in organic morphology can
be adequately appreciated only by those who, like myself, were brought
up in the school of the old teleological morphology, and whose eyes
were suddenly opened by the theory of selection to a comprehension of
that greatest of all biological riddles, the creation of specific
forms. The dogma of creation, the mystic and dualistic doctrine of the
isolated creation of each separate variety, was annihilated at one
blow; the belief in transmutation has now for ever taken its
place--the mechanistic and monistic doctrine of the metamorphosis of
organic forms, of the descent of all the species of one natural class
from a common parent-form. How complete a change the science of
mechanical morphology has by this means been compelled to undergo, I
have endeavoured to point out in my "General Morphology;" and any one
who wishes to convince himself clearly of what an enormous revolution
has been brought about, particularly in comparative anatomy, may
compare the "Outlines of Comparative Anatomy" (Grundzuege der
vergleichenden Anatomie), by Carl Gegenbaur, 1870, and the latest
edition of his "Elements" (Grundrisses), with the old text-books of
that science.
Virchow has no suspicion even of all these immeasurable strides in
morphology, for this department always lay out of his ken. His great
reforms in pathology were founded in the province of physiology, and
more especially in cellular physiology. But within the last twenty
years these two main branches of biological inquiry have grown more
and more apart. The great Johannes Mueller was the last biologist who
was able to keep these departments of organic inquiry together, and
who won equally immortal honours in both divisions of the subject.
After Mueller's death in 1858 they fell asunder. Physiology, as the
science especially of the functions or living activity of the
organism, addressed itself more and more to exact and experimental
methods: morphology, on the contrary, as the science of the forms and
structure of animals and plants, could naturally make but very small
use of this method; it must take refuge more and more in the history
of evolution, and so constitute an historical natural science. It was
on this very historical and genetic method of morphology, in
contradistinction to the exact and experimental method of physiology,
that I based my Munich address; and if Virchow in his answer had
really and thoroughly refuted this position, instead of fighting with
mere phrases and denunciations, this radical opposition would have
been well worthy of the fullest discussion. At the same time I have
no wish to reproach Virchow for being wholly fettered by the one-sided
views of the modern school-physiology, nor because morphology lies so
far out of his ken that he has not been able to form an independent
judgment of its aims and methods; but when, in spite of all this, he
on every occasion lets fall a disparaging judgment of it, we must
dispute his competence. It is true that in his Munich address he
emphasises the statement, "That which graces me best is that I know my
ignorance," by printing it in italics. I only regret that I am forced
to deny his possession of this very grace. Virchow does not know how
ignorant he is of morphology, else he would never have uttered his
annihilating verdict on it, else he would not continually designate
the study of the theory of descent as dilettanteism and vain dreaming,
as "a fanciful private speculation which is now making its way in
several departments of natural science." In truth, Virchow does me
greatly too much honour when he designates as my "personal crotchet"
an idea which for the last ten years has been the most precious common
possession of all morphological science. If Virchow were not so
unfamiliar with the literature of morphology, he must have known that
it is penetrated throughout by this principle of descent, that every
morphological inquiry which conscientiously pursues a well-considered
problem now assumes the doctrine of descent as granted and
indisputable. Of all this he is ignorant, and so it is intelligible
that he should continue to demand "certain proofs" of this hypothesis,
although those proofs have long since been produced.
FOOTNOTES:
[12] Vol. ii., p. 334 of translation.
[13] London: C. Kegan Paul & Co. 1879.
[14] Jena, Zeitschriften fuer Naturwissenschaft, 1875. Vol. x.
Supplement.