Other Instances Of Dissatisfaction With The Theory Of Descent





What was with Virchow only a suggestion of the need for caution, or

controversial matter to be subsequently allowed for or contradicted, had

more serious consequences to others, and led to still greater hesitancy as

regards evolutionist generalisations and speculations, and sometimes to

sharp antagonism to them.



One of the best known of the earlier examples of this mood is Kerner von

Marilaun's large and beautiful work on "Plant Life."(21) He does, indeed,

admit that our species are variations of antecedent forms, but only in a

very limited sense. Within the stocks or grades of organisation which have

always existed, variations have come about, through "hybridisation,"

through the crossing of similar, but relatively different forms; these

variations alter the configuration and appearance in detail, but neither

affect the general character nor cause any transition from "lower" to

"higher."



Kerner disposes of the chief argument in favour of the theory of descent,

the homology of individual organs, by explaining that the homology is due

to the similarity of function in the different organisms. A similar

argument is used in regard to "ontogeny recapitulating phylogeny."

Palaeontology does not disclose in the plant-world any "synthetic types,"

which might have been the common primitive stock from which many now

divergent branches have sprung, nor does it disclose any "transition

links" really intermediate, for instance, between cryptogams and

gymnosperms, or between gymnosperms and angiosperms. That the higher races

are apparently absent from the earlier strata is not a proof that they

have never existed. The peat-bog flora must have involved the existence of

a large companion-flora, without which the peat could not have been

formed, but all trace of this is absent in the still persistent vestiges

of these times.(22) Life, with energy and matter, has existed as a

phenomenon of the universe from all eternity, and thus its chief forms and

manifestations have not "arisen," but have always been. If facts such as

these contradict the Kant-Laplace theory of the universe, then the latter

must be corrected in the light of them, not conversely. The extreme

isolation of Kerner and his theory is probably due especially to this

corollary of his views.



Among the most recent examples of antagonism to the Evolution-Theory, the

most interesting is a book by Fleischmann, professor of zoology in

Erlangen, published in 1901, and entitled, "The Theory of Descent." It

consists of "popular lectures on the rise and decline of a scientific

hypothesis" (namely, the Theory of Descent), and it is a complete

recantation by a quondam Darwinian of the doctrine of his school, even of

its fundamental proposition, the concept of evolution itself. For

Fleischmann is not guilty, like Weismann, of the inaccuracy of using

"Theory of Descent" as equivalent to Darwinism; he is absolutely

indifferent to the theory of natural selection. His book keeps strictly to

matters of fact, and rejects as speculation everything in the least beyond

these; it does not express even an opinion on the question of the origin

of species, but merely criticises and analyses.



It does not bring forward any new and overwhelming arguments in refutation

of the Theory of Descent, but strongly emphasises difficulties that have

always beset it, and discusses these in detail. The old dispute which

interested Goethe, Geoffroy St. Hilaire, and Cuvier, as to the unity or

the fundamental heterogeneity of the "architectural plan" in nature is

revived. Modern zoology recognises not merely the four types of Cuvier,

but seventeen different styles, "phyla," or groups of forms, to derive one

of which from another is hopeless. And what is true of the whole is true

also of the subdivisions within each phylum; e.g., within the vertebrate

phylum with its fishes, amphibians, reptiles, birds and mammals. No bridge

leads from one to the other. This is proved particularly by the very

instance which is the favourite illustration in support of the Theory of

Descent--the fin of fishes and its relation to the five-fingered hand of

vertebrates. The so-called transition forms (Archaeopteryx, monotremes,

&c.) are discredited. So with the "stalking-horse" of evolutionists--the

genealogical tree of the Equidae, which is said to be traceable

palaeontologically right back, without a break, from the one-toed horses of

the present day to the normal five-toed ancestry; and so with another

favourite instance of evolution, the history of the pond-snails

(Planorbis multiformis), the numerous varieties of which occur with

transitions between them in actual contiguity in the Steinheim beds, and

thus seem to afford an obvious example of the transformation of species.

Against these cases, and against using the palaeontological archives as a

basis for the construction of genealogical trees in general, the weighty

and apparently decisive objection is urged, that nowhere are the soft

parts of the earlier forms of life preserved, and that it is impossible to

establish relationships with any certainty on the basis of hard parts

only, such as bones, teeth and shells. Even Haeckel admits that snails of

very different bodily structure may form very similar and even hardly

distinguishable shells.



Fleischmann further asserts that Haeckel's "fundamental biogenetic law"

has utterly collapsed. "Recapitulation" does not occur. Selenka's figures

of ovum-segmentation show that there are specific differences in the

individual groups. The origin and development of the blastoderm or

germinal disc has nothing to do with recapitulation of the phylogeny. It

is not the case that the embryos of higher vertebrates are

indistinguishable from one another. Even the egg-cell has a specific

character, and is totally different from any unicellular organism at the

Protistan level. The much-cited "gill-clefts" of higher vertebrates in the

embryonic stage are not persistent reminiscences of earlier lower stages;

they are rudiments or primordia shared by all vertebrates, and developing

differently at the different levels; (thus in fishes they become breathing

organs, and in the higher vertebrates they become in part associated with

the organs of hearing, or in part disappear again).



Though Fleischmann's vigorous protest against over-hastiness in

construction and over-confidence on the part of the adherents of the

doctrine of descent is very interesting, and may often be justified in

detail, it is difficult to resist the impression that the wheat has been

rejected with the chaff.(23)



Even a layman may raise the following objections: Admitting that the great

groups of forms cannot be traced back to one another, the palaeontological

record still proves, though it may be only in general outline, that within

each phylum there has been a gradual succession and ascent of forms. How

is the origin of what is new to be accounted for? Without doing violence

to our thinking, without a sort of intellectual autonomy, we cannot rest

content with the mere fact that new elements occur. So, in spite of all

"difficulties," the assumption of an actual descent quietly forces

itself upon us as the only satisfactory clue. And the fact, which

Fleischmann does not discuss, that even at present we may observe the

establishment of what are at least new breeds, impels us to accept an

analogous origin of new species. Even if the biogenetic law really "finds

its chief confirmation in its exceptions," even if we cannot speak of a

strict recapitulation of earlier stages of evolution, there are

indisputable facts which are most readily interpreted as reminiscences, as

due to affiliation (ideal or hereditary), with ancestral forms. (Note, for

instance, Weismann's "prediction," &c.(24)) Even if Archaeopteryx and other

intermediate forms cannot be regarded as connecting links in the strict

sense, i.e., as being stages in the actual pedigree, yet the occurrence

of reptilian and avian peculiarities side by side in one organism, goes

far to prove the close relationship of the two classes.



Fleischmann's book strengthens the impression gained elsewhere, that a

general survey of the domain of life as a whole gives force and

convincingness to the Theory of Descent, while a study of details often

results in breaking the threads and bringing the difficulties into

prominence. But the same holds true of many other theoretical

constructions, and yet we do not seriously doubt their validity. (Take,

for instance, the Kant-Laplace theory, and theories of ethnology, of the

history of religion, of the history of language, and so on.) And it is

quite commonly to be observed that those who have an expert and specialist

knowledge, who are aware of the refractoriness of detailed facts, often

take up a sceptical attitude towards every comprehensive theory, though

the ultimate use of detailed investigation is to make the construction of

general theories possible. Fleischmann does exactly what, say, an

anthropologist would do if, under the impression of the constancy and

distinctiveness of the human races, which would become stronger the more

deeply he penetrated, he should resignedly renounce all possibility of

affiliating them, and should rest content with the facts as he found them.

Similarly, those who are most intimately acquainted with the races of

domesticated animals often resist most strenuously all attempts, although

these seem to others a matter of course, to derive our "tame" forms from

"wild" species living in freedom.



But to return. Even where the Theory of Descent is recognised, whether

fully or only half-heartedly, the recognition does not always mean the

same thing. Even the adherents of the general, but in itself quite vague

view that a transformation from lower forms to higher, and from similar to

different forms, has taken place, may present so many points of

disagreement, and may even stand in such antagonism to one another, that

onlookers are apt to receive the impression that they occupy quite

different standpoints, and are no longer at one even in the fundamentals

of their hypotheses.



The most diverse questions and answers crop up; whether evolution has been

brought about "monophyletically" or "polyphyletically," i.e., through

one or many genealogical trees; whether it has taken place in a continuous

easy transition from one type to another, or by leaps and bounds; whether

through a gradual transformation of all organs, each varying individually,

or through correlated "kaleidoscopic" variations of many kinds throughout

the whole system; whether it is essentially asymptotic, or whether

organisms pass from "labile" phases of vital equilibrium by various

halting-places to stable states, which are definitive, and are, so to

speak, the blind alleys and terminal points of evolutionary possibilities,

e.g., the extinct gigantic saurians, and perhaps also man. And to these

problems must be added the various answers to the question, What precedes,

or may have preceded, the earliest stages of life of which we know? Whence

came the first cell? Whence the first living protoplasm? and How did the

living arise from the inorganic? These deeper questions will occupy us in

our chapter on the theory of life. Some of the former, in certain of their

aspects, will be considered in the sixth chapter, which deals with factors

in evolution.



The Theory of Descent itself and the differences that obtain even among

its adherents can best be studied by considering for a little the works of

Reinke and of Hamann.



Reinke, Professor of Botany in Kiel, has set forth his views in his book,

"Die Welt als Tat,"(25) and more recently in his "Einleitung in die

theoretische Biologie" (1901). Both books are addressed to a wide circle

of readers. Reinke and Hamann both revive some of the arguments and

opinions set forth in the early days of Darwinism by Wigand,(26) an author

whose works are gradually gaining increased appreciation.



It is Reinke's "unalterable conviction" that organisms have evolved, and

that they have done so after the manner of fan-shaped genealogical trees.

The Theory of Descent is to him an axiom of modern biology, though as a

matter of fact the circumstantial evidence in favour of it is extremely

fragmentary. The main arguments in favour of it appear to him to be the

general ones; the homologies and analogies revealed by comparative

morphology and physiology, the ascending series in the palaeontological

record, vestigial organs, parasitic degeneration, the origin of those

vital associations which we call consortism and symbiosis. These he

illustrates mainly by examples from his own special domain and personal

observation.



The simplest unicellular forms of life are to be thought of as at the

beginning of evolution; and, since mechanical causes cannot explain their

ascent, it must be assumed that they have an inherent "phylogenetic

potential of development," which, working epigenetically, results in

ascending evolution. He leaves us to choose between monophyletic and

polyphyletic evolution, but himself inclines towards the latter,

associating with it a rehabilitation of Wigand's theory of the primitive

cells. If, in the beginning, primitive forms of life arose (probably as

unicellulars) from the not-living, it is not obvious why we need think of

only one so arising, and, if many did so, why they should not have

inherent differences which would at once result in typically different

evolutionary series and groups of forms. But evolution does not go on ad

libitum or ad infinitum, for the capacity for differentiation and

transformation gradually diminishes. The organisation passes from a labile

state of equilibrium to an increasingly stable state, and at many points

it may reach a terminus where it comes to a standstill. Man, the dog, the

horse, the cereals, and fruit trees appear to Reinke to have reached their

goal. The preliminary stages he calls "Phylembryos," because they bear to

the possible outcome of their evolution the same relation that the embryo

does to the perfect individual. Thus, Phenacodus may be regarded as the

Phylembryo of the modern horse. It is quite conceivable that each of our

modern species may have had an independent series of Phylembryos reaching

back to the primitive cells. But the palaeontological record, and

especially its synthetic types, lead Reinke rather to assume that instead

of innumerable series, there have been branching genealogical trees, not

one, however, but several.



These views, together or separately, which are characterised chiefly by

the catch-words "polyphyletic descent," "labile and stable equilibrium,"

and so on, crop up together or separately in the writings of various

evolutionists belonging to the opposition wing. They are usually

associated with a denial of the theory of natural selection, and with

theories of "Orthogenesis," "Heterogenesis," and "Epigenesis."



We shall discuss them later when we are considering the factors in

evolution. But we must first take notice of a work in which the theories

opposed to Darwinian orthodoxy have been most decisively and aggressively

set forth. As far back as 1892 O. Hamann, then a lecturer on zoology in

Goettingen, gathered these together and brought them into the field,

against Haeckel in particular, in his book "Entwicklungslehre und

Darwinismus."(27)



Hamann's main theme is that Darwinism overlooks the fact that "there

cannot have been an origin of higher types from types already finished."

For this "unfortunate and unsupported assumption" there are no proofs in

embryology, palaeontology, or anatomy. He adopts and expands the arguments

and anti-Haeckelian deliverances of His in embryology, of Snell and Heer

in palaeontology, of Koelliker and von Baer in their special interpretation

of evolution, of Snell particularly as regards the descent of man. It is

impossible to derive Metazoa from Protozoa in their present finished state

of evolution; even the Amoeba is so exactly adapted in organisation and

functional activity to the conditions of its existence that it is a

"finished" type. It is only by a stretch of fancy that fishes can be

derived from worms, or higher vertebrates from fishes. One of his

favourite arguments--and it is a weighty one, though neglected by the

orthodox Darwinians--is that living substance is capable, under similar

stimuli, of developing spontaneously and afresh, at quite different points

and in different groups, similar organs, such as spots sensitive to light,

accumulations of pigment, eye-spots, lenses, complete eyes, and similarly

with the notochord, the excretory organs, and the like. Therefore homology

of organs is no proof of their hereditary affiliation.(28) They rather

illustrate "iterative evolution."



Another favourite argument is the fact of "Paedogenesis." Certain animals,

such as Amphioxus lanceolatus, Peripatus, and certain Medusae, are very

frequently brought forward as examples of persistent primitive stages and

"transitional connecting links." But considered from the point of view of

Paedogenesis, they all assume quite a different aspect, and seem rather to

represent very highly evolved species, and to be, not primitive forms, but

conservative and regressive forms. Paedogenesis is the phenomenon exhibited

by a number of species, which may stop short at one of the stages of their

embryonic or larval development, become sexually mature, and produce

offspring without having attained their own fully developed form.



Another argument is the old, suggestive, and really important one urged by

Koelliker, that "inorganic nature shows a natural system among minerals

(crystals) just as much as animals and plants do, yet in the former there

can be no question of any genetic connection in the production of forms."



Yet another argument is found in the occurrence of "inversions" and

anomalies in the palaeontological succession of forms, which to some extent

upsets the Darwinian-Haeckelian genealogical trees. (Thus there are forms

in the Cambrian whose alleged ancestors do not appear till the Silurian.

Foraminifera and other Protozoa do not appear till the Silurian.)



From embryology in particular, as elsewhere in general, we read the

"fundamental biogenetic law," that evolution is from the general to the

special, from the imperfect to the more perfect, from what is still

indefinite and exuberant to the well-defined and precise, but never from

the special to the special. According to Hamann's hypothesis we must think

of evolution as going on, so to speak, not about the top but about the

bottom. The phyla or groups of forms are great trunks bearing many

branches and twigs, but not giving rise to one another. Still less do the

little side branches of one trunk bear the whole great trunk of another

animal or plant phylum. But they all grow from the same roots among the

primitive forms of life. Unicellulars these must have been, but not like

our "Protists." They should be thought of as primitive forms having within

themselves the potentialities of the most diverse and widely separate

evolution-series to which they gave rise, as it were, along diverging

fan-like rays.



It would be instructive to follow some naturalist into his own particular

domain, for instance a palaeontologist into the detailed facts of

palaeontology, or an embryologist into those of embryology, in order to

learn whether these corroborate the assumptions of the Theory of Descent

or not. It is just in relation to these detailed facts that criticisms or

even denials of the theory have been most frequent. Koken, otherwise a

convinced supporter of the theory, inquires in his "Vorwelt," apropos of

the tortoises, what has become of the genealogical trees that were

scattered abroad in the world as proved facts in the early days of

Darwinism. He asserts, in regard to Archaeopteryx, the instance which is

always put forward as the intermediate link in the evolution of birds,

that it does not show in any of its characters a fundamental difference

from any of the birds of to-day, and further, that, through convergent

development under similar influences, similar organs and structural

relations result, iterative arrangements which come about quite

independently of descent. He maintains, too, that the principle of the

struggle for existence is rather disproved than corroborated by the

palaeontological record.



In embryology, so competent an authority as O. Hertwig--himself a former

pupil of Haeckel's--has reacted from the "fundamental biogenetic law." His

theory of the matter is very much that of Hamann which we have already

discussed; development is not so much a recapitulation of finished

ancestral types as the laying down of foundations after the pattern of

generalised simple forms, not yet specialised; and from these foundations

the special organs rise to different levels and grades of differentiation

according to the type.(29) But we must not lose ourselves in details.



Looking back over the whole field once more, we feel that we are justified

in maintaining with some confidence that the different pronouncements in

regard to the detailed application and particular features of the Theory

of Descent, and the different standpoints that are occupied even by

evolutionists, are at least sufficient to make it obvious that, even if

evolution and descent have actually taken place, they have not run so

simple and smooth a course as the over-confident would have us believe;

that the Theory of Descent rather emphasises than clears away the riddles

and difficulties of the case, and that with the mere corroboration of the

theory we shall have gained only something relatively external, a clue to

creation, which does not so much solve its problems as restate them. The

whole criticism of the "right wing," from captious objections to actual

denials, proves this indisputably. And it seems likely that in the course

of time a sharpening of the critical insight and temper will give rise to

further reactions from the academic theory as we have come to know it.(30)

On the other hand, it may be assumed with even greater certainty that the

general evolutionist point of view and the great arguments for descent in

some form or other will ultimately be victorious if they are not so

already, and that, sooner or later, we shall take the Theory of Descent in

its most general form as a matter of course, just as we now do the

Kant-Laplace theory.





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