The strongest evidence of the decay of Darwinism is to be found in the
fact that, since Darwin first enunciated his theory, many and diverse
attempts have been made to explain the origin of species on other
principles. Names of men, like M. Wagner, Naegeli, Wigand, Koelliker,
and Kerner mark these attempts; but of these investigators Naegeli
alone proposed a well-developed hypothesis. Finally, however, Eimer,
professor of zoology in Tuebingen came forward with a detailed theory
of Descent. As early as 1888 he published a comprehensive work dealing
with it, under the title: "The Origin of Species by Means of the
Transmission of Acquired Characters According to the Laws of Organic
Growth." As the title itself indicates, a very marked divergence was
even at that time manifesting itself between Eimer and his former
teacher and friend, the great defender of Darwinism in Germany, Aug.
Weismann, professor of zoology in Freiburg in Breisgau. For, while the
latter vigorously attacks the transmission of acquired characters,
Eimer's whole theory is founded on this very transmission. Observations
regarding the coloring of animals, in fact, form the basis of Eimer's
theory.
Eimer attributes the origin of species to "organic growth" by which he
means not merely increase in size, but also change of form, etc. This
growth does not proceed blindly or aimlessly, but proceeds on rigidly
determined lines, which depend upon the structure and constitution of
the particular organism. External influences, however, also affect it.
Eimer specially emphasizes four points in this connection: 1. This
rigidly determined development of a character exhibits well defined,
regular stages, and the evolution of each individual repeats the whole
series of transformations (the Mueller-Haeckel "biogenetic-law.") 2.
New characters are first acquired by strong adult males (the law of
male dominance). 3. New characters appear on definite parts of the
body, spreading especially from the rear to the front, (the law of
undulation). 4. Varieties are stages in the process of development,
through which all the individuals of the respective species must pass.
These points indicate how important for Eimer is the transmission of
those characters which the parents themselves have acquired in the
course of their own development. He conceives that this transmission
takes place when the causative influences exert themselves permanently
on many succeeding generations. Eimer thinks that in this way the
constitution of the respective species is gradually transformed.
Besides the effect of external influences (which may vary according to
the climate, etc.: Geoffroy St. Hilaire), Eimer mentions as important
and active factors in this development, (1). The use and disuse of
organs (Lamarck); (2). The struggle for existence (Darwin); (3). The
correlation of organs, that is, the inner relation of organs in
consequence of which a change in one organ may occasion a sudden change
in another organ; (4). Cross fertilization and hybridism.
It is clear that with reference to the factors of evolution Eimer is,
and perhaps not unreasonably, an eclectic, whose aim is to do justice
to the predecessors of Darwin as well as to Darwin himself. His
antagonism to Darwin and Weismann in this work is still quite moderate,
although even here it appears with sufficient clearness that selection
and the struggle for existence, the two principles peculiarly
characteristic of Darwinism, do not give rise to new species, but can
at best only separate and differentiate species already existing.
The second part of Eimer's work dealing with the origin of species,
which appeared after an interval of ten years, bears the title:
"Orthogenesis of Butterflies." The Origin of Species, II. Part (2
tables and 235 illustrations in the text). Leipzig, 1897. In this book
substantially the same thoughts occupy the mind of the author as in the
former volume, but in many respects they are more mature, and
conspicuously more definite and precise. The most salient features are
the following:
1. Eimer establishes his theory by means of very minute observations on
a definite species of animals, viz., butterflies.
2. He attributes evolution almost exclusively to development along
definitely determined lines.
3. He proves the utter untenableness of Darwinian principles and
repudiates them unqualifiedly.
4. In a very distinct and severe manner he gives expression to his
opposition to his former friend Weismann.
5. He attacks with telling effect the fantastic Darwinian "Mimicry."
In his "General Introduction" Eimer first treats of Orthogenesis in
opposition to the Darwinian theory of selection. The very first
sentence gives evidence of this antagonism: "According to my
investigation, organic growth (Organophysis), which is rendered
dependent on the plasm by permanent external influences, climate and
nourishment, and the expression of which is found in development along
definitely determined lines, (Orthogenesis), is the principal cause of
transformation, its occasional interruption and its temporary cessation
and is likewise the principal cause of the division of the series of
organisms into species."
Lamarck's theory of the use and disuse of organs and Darwin's
hypothesis of natural selection are consequently pushed into the
background. Here also Eimer at once places himself at variance with
Naegeli who had enunciated a similar theory. Naegeli took as a starting
point an inherent tendency in every being to perfect itself, thus
presupposing an "inner principle of development," and making light of
external influences as transforming causes. Eimer flatly contradicts
this view. We shall revert to this point in our criticism of his
theory. In opposition to the theory of selection, Eimer lays special
stress on the fact that its underlying assumption, viz., fortuitous,
indefinite variation in many different directions, is entirely devoid
of foundation in fact, and that selection, in order to be effective,
postulates the previous existence of the required useful characters,
whereas the very point at issue is to explain how these characters have
originated. Since, therefore, according to Eimer's investigations,
there are everywhere to be found only a few, definitely determined
lines of variation, selection is incapable of exercising any choice.
The development, furthermore, proceeds without regard for utility,
since, for instance, the features that characterize a species of plants
are out of all reference to utility. "Even if nothing exists that is
essentially detrimental, nevertheless very much does exist that bears
no reference whatever to immediate good, and was therefore never
affected by selection."
Further on, Eimer expresses still more clearly the opposition of his
theory to that of Darwin, and in so doing he attacks vigorously the
omnipotence of selection, so unreasonably proclaimed by the followers
of Darwin. Eimer's theory, consequently, asserts that: "The essential
cause of transmutation is organic growth, a definite variation, which,
during long periods of time proceeds unswervingly and without reference
to utility, in but few directions and is conditioned by the action of
external influences, of climate and nourishment." In consequence of an
interruption of orthogenesis a stoppage ensues in certain stages of the
development, and this stoppage is the great cause of the arrangement of
forms in different species. Of vital importance also "is development
through different stages (Hetero-epistase), which results in the
arrested development of certain characters in an organism, while others
progress and still others become retrogressive. As a rule use and
disuse are of great efficacy in this regard, and conjointly with these
compensation and correlation." Occasionally also irregular development
sets in, which proceeds by leaps.
Of course, Eimer could not but in his turn burn incense before Darwin
by declaring that he would not dare to cross swords with such a man,
while in reality he repudiates all of Darwin's fundamental tenets.
It may be well to state here in addition a few important supplementary
considerations: "Development can everywhere proceed in only a limited
number of directions because the constitution, the material composition
of the body, conditions these directions and prevents variation in all
directions." This is an important statement because Eimer clearly
expresses therein the difference between his own theory and that of
Naegeli. He makes the direction of development dependent on the
material composition of the body, whereas Naegeli considers it
dependent upon an internal tendency of every being to perfect itself,
hence upon a power inherent in the body. Eimer's view therefore tends
towards a mechanical explanation, while Naegeli postulates a vital
energy. The "internal causes" according to Eimer find their explanation
in the material composition of the body. Since the growth of the
individual organism depends on this composition and on the external
influences, Eimer compares family-development with it and designates
the latter as "organic growth." In opposition to Naegeli he maintains
that this "organic growth" does not always aim at perfection but often
tends to simplification and retrogression.
The following, then, according to Eimer, are the directive principles
of variation: (1). The general law of coloration (stripes running
lengthwise change into spots, stripes running crosswise change to a
uniform color). (2). The law of definitely directed local change (new
colors spread from the rear to the front and from above downward or
vice versa, old colors disappear in the same directions.) (3). The law
of male predominance (males are as a rule one step in advance of the
females in development). Female predominance is an exception. (4). The
law of age-predominance (new characters appear at a well-advanced age,
and at the time of greatest strength). (5). The law of wave-like
development (during the course of the formation of the individual
organism a series of changes proceed in a definite direction over the
body of the animals). (6). The law of independent uniformity of
development (the same course of development is pursued in non-related
forms and results in similar forms). (7). The law of development
through different stages (different characteristics of the same being
may develop to a different degree and in different directions). (8).
The law of unilateral development (the progeny does not present a
complete combination of the characters of the parents but manifests a
preponderance of the characteristics of either parent). (9). The law of
the reversal of development (the direction of development may reverse
and tend towards the starting point). (10). The law of the cessation of
development (a protracted cessation of development frequently ensues in
one or the other stage).
The origin (perhaps rather the distinction) of species is accounted for
principally by the last named law, by means of which Eimer also
explains the so-called atavism or reversion. To this law are joined
other factors, e.g., development proceeding in leaps, as demonstrated
by Koelliker and Heer; local separation (through migration; prevention
of fertilization, e.g., the impossibility of cross-fertilization
between certain individual organisms) which Romanes had already opposed
to natural selection, and crossing.
The second main division of the book is taken up with a very searching
and detailed criticism of Weismann. This criticism seems to me entirely
warranted; because not only the latter's unintelligible position with
regard to natural selection (the repudiation of which he seems to
regard as synonymous "with cessation of all investigation into the
causal nexus of phenomena in the domain of life") but likewise his
fanciful theory of heredity, utterly devoid as it is of any support
from actual observation, bespeak an utter lack of qualities essential
to a naturalist; and the manner in which he ignores his former pupil
and his labors, because they proved embarrassing to him, is entirely
unworthy of a man of science.
Eimer devotes special attention to "mimicry"; and indeed he was forced
to be very solicitous to dispel this fanciful conception of Darwinism
which radically contradicted his own views. Moreover, the untenableness
of the mimicry hypothesis must have revealed itself very clearly to him
in the course of his investigations regarding the coloring of
butterflies. Mimicry, as our readers are well aware, consists in this,
that living beings imitate other organisms or even inanimate objects;
Darwinism maintains that this is done for the sake of protection
against enemies. This phenomenon is said to have been produced by
selection. Those animals that possessed, for instance, some similarity
to a leaf, in consequence escaped their enemies more easily than others
and survived, while those that had no leaf-like appearance succumbed;
when this process had been repeated a few times, many animals
(butterflies) gradually developed that marvelous leaf-like appearance,
which frequently deceives the most practiced eye.
It appears so simple and natural that one need not wonder that this
peculiar phenomenon gained many an adherent for Darwinism. But, of
course, it is directly opposed to the views of Eimer; and it is for
this reason that he endeavors so assiduously to disprove the error of
Darwinism in this regard. As the underlying color design of the
butterfly Eimer designates eleven longitudinal designs; and the
examination of the leaf-like forms leads him to the conclusion, that
their appearance always depends on "the unaltered condition or the
greater prominence of certain parts of this fundamental design." There
is to be observed a shifting of the third band, so that in conjunction
with the fourth, which is curved, it forms the mid-rib of the leaf.
Eimer finds the cause of this phenomenon in the alteration of the form.
The leaf-like form results from an acumination and elongation of the
wings, which in turn results from a marked elongation of the rim of the
fore-wing. And this again is produced by the proportionately greater
growth of one part of the wing-section than of the others.
With reference to the reason of this growth it is of importance to note
that experiments, consisting in the application of artificial heat to
the chrysales of the swallow-tail and sailor-butterfly, demonstrated
that by this means "the fore-wing is drawn out more toward the outer
wing-vein, and the rim of the fore-wing becomes more elongated and
curved." It is observed, however, that the natural heat-forms of the
same genera and species, namely, the summer-forms and those which live
in the warm southern climate, exhibit, for instance, in the case of
butterflies akin to the sailor, the same features, the elongation and
more marked curvature of the fore-rim of the fore-wings and the
consequent more extended form, that are produced by the action of
artificial heat. Manifestly this is a matter of vital importance for
the solution of the question: heat, whether artificial or natural,
produces a difference in growth, which results in a change of form and
coloring. There is consequently no room for natural selection or the
struggle for existence.
The leaf-like form is generally associated with the dark, faded colors
of dry leaves, and when this similarity disappears even bright colors
appear on the fore-wings. In many cases the resemblance to leaves is
very imperfect; different forms of the same species live side by side
and among them are to be found those, the resemblance of which to
leaves is extremely slight. All these facts, and especially the
frequently recurring retrogression of the leaf-like appearance, justify
serious doubt regarding the Darwinian assumption, that adaptation was a
necessity for the forest-butterflies on account of the protection which
it provided.
An eye witness furthermore declares that the butterflies that resemble
leaves most closely do not always alight on withered leaves, on which
they would be almost invisible, but frequently rest on a green
background, against which they show off very clearly, and therefore
could not long escape the keen eye of birds. Besides, these butterflies
are but seldom pursued by the birds, of which there is question here,
and hence are in no need of protection.
The longer Eimer devoted his attention to the origin of this
resemblance the more "the poetic picture of the imitated leaf" vanished
out of sight, and he became convinced that it involved the necessary
expression of the lines of development, which the respective beings
were bound to follow, and that there was no question of imitation.
Apart from the resemblance to leaves, by reason of regular changes of
color, design, and wing-structure, numerous non-related butterflies
often develop such wonderful similarities--which are not, as hitherto
supposed, imitations or disguises produced by selection, but are either
the outcome of an entirely independent uniformity of development or, at
least, of its consequence--that it must be admitted that external
similarity may arise by different means and in various ways. These
relations of similarity are of such frequent recurrence because of the
limited number of directions of development in which changes or color
and design in butterflies may tend. Eimer finds the reason of this
small number of directions, in which development may proceed, in the
fact "that the elementary external influences of climate and
nourishment on the constitution of the organism are everywhere the
cause of the transformations."
Another important point is the difference of sex. If the butterflies
are of different sex, the males as a rule exhibit a more developed
stage of design and color than the females. These frequently present on
the upper side the stage of coloration, which the males present on the
lower side, while the upper side of the males is one stage in advance.
It is of special significance that the characters of the more advanced
sex frequently correspond to those of a related, superior species, and
occasionally to those of widely separated species. Eimer endeavors to
explain male predominance "by a more delicate and more developed, i.e.,
more complex, chemico-physical organization of the male organism." Even
this development tends toward simplification, the origin of dull-black
colors.
This most interesting question brings Eimer into conflict with another
Darwinian principle, the so-called principle of "sexual election,"
according to which the more striking characteristics of the male sex
become strengthened for the reason that females invariably give the
preference to the males endowed with them, over those that are less
"attractive." These exceedingly romantic ideas have been often and
deservedly repudiated, e.g., even by Wallace only a short time after
their first appearance. Eimer really does them too much honor when he
again undertakes, even with a certain amount of respect, a thorough
refutation of them, "as in every regard unfounded." It is of primary
importance to note here, that in the case of dimorphism of the sexes
abrupt modifications occur in connection with unilateral heredity. "It
is impossible for sexual selection to produce a change of design and
color, which results in the sudden kaleidoscopic formation of wholly
different designs, as we find actually taking place through the action
of artificial heat and cold and other factors in nature."
This brings us to a brief consideration of the answer, which Eimer
proposes to give to the question of the real causes of the formation of
species among butterflies. A precise and clear statement of this
important part of Eimer's theory of Descent, is contained in the
following extracts: "The transformation of organisms is primarily
conditioned by the action of immediate external influences on the
organisms. The same causes, which produce individual growth, especially
climate and nourishment, also produce the organic growth of organisms,
that is, transmutation, which is but a continuation in the progeny of
individual growth, through the transmission of the characteristics
acquired during the lifetime of the individual."
Hence, transmutation is simply a physiological process, a phyletic
growth.
"The changes, which the individual organism experiences during its life
in its material, physiological and morphological organization, are in
part transmitted to its progeny. The changes thus acquired become more
marked from generation to generation, until finally they result in a
perceptible new structure."
"In this process, new or changing external influences undoubtedly
exercise great activity, but the same influences, constantly repeated,
must in the course of time also produce a change in the organisms
through the physiological activity, which is conditioned by them, so
that after a long time elapses, a species will have changed even in an
unvarying environment and will react on new influences in a manner
quite different from their progenitors; their "constitution" has
undergone a change."
"This organic growth of living beings takes place regardless of the
active use of the organs and in many cases remains independent of this
(Lamarckian) factor of transformation. But use may exercise
considerable influence on the formation resulting from the primitive
organic growth, by modifying the growth, by restricting it to those
parts most frequently called into use, or even by depriving other parts
of the necessary matter (compensation)."
"The Lamarckian principle, therefore, offers but a possible and to
transformation, the principal cause is to be found in organic growth."
"* * * The organic growth of butterflies is primarily conditioned by
climatic influences. * * * The proof is to be found in the facts
revealed by the geographical distribution of butterflies, by the
variations corresponding to the seasons, and by experiments regarding
the influence of artificial heat and cold on development."
Experimental proof is naturally of vital importance for Eimer's theory.
He cites in this regard especially the experiments of Merrifield,
Handfuss, Fischer, Fickert, and Countess Maria von Linden. In Eimer's
own laboratory the latter performed experiments on Papilionides, "which
prove in the most striking manner the recapitulation of the
family-history in the individual." "The fact that it is possible by
raising or lowering the temperature during the time of development to
breed butterflies, possessed of the characteristics of related
varieties and species living in southern and northern regions
respectively, characteristics not merely of color and design, but also
of structure, is complete irrefragable proof of my views."
Eimer therefore belongs to the class of naturalists, like Wigand,
Askenasy, Naegeli, and many others, who reject the purely mechanical
trend of Darwinism and recognize an "immanent principle of
development." He seeks the essential cause of evolution in the
constitution of the plasm of organisms. This very analogy between the
development of the family and that of the individual should, in fact,
convince any one of this. If Eimer chooses to refer the analogy to
"growth" and to designate the evolution of the whole animated kingdom
as also a process of growth, there is, strictly speaking, no room for
objection. However, there is here a danger, which he does not seem to
have guarded against. To designate the whole process as a growth, as
Eimer does, really explains nothing, but merely defines more clearly
the status of the problem. For, what do we know of the so-called
process of growth? In truth, nothing, so that very little is gained by
referring evolution to organic growth; the problem remains unsolved.
The most important and correct part of Eimer's conclusion seems to be
the establishment of definite lines of development. He has, in fact,
permanently disposed of the Darwinian assumption of universal chaos in
evolution, upon which good mother Nature could at will exercise her
choice. Fortuitously initiated development is a condition sine qua non
of Darwinism and Weismannism. For any one, who has studied the work of
Eimer and still adheres to this fundamental error of Darwinism, there
is no possible escape from the labyrinth into which he has allowed the
hand of Darwinism to lead him.
If, on the one hand, Eimer recognizes the immanent principles of
development, he, nevertheless, on the other hand, also accords due
consideration and ascribes great efficacy to external influences; in
fact, he represents them as perhaps the more essential factor. Climate,
nourishment, etc., affect the inner structure, the plasm, transform it
and thus produce variation which is transmitted to the progeny. But,
however great may be the influence of environment, Eimer seems to
overestimate it. Indeed, the analogy of "growth" should have led Eimer
to a conception of the true relation between "internal" and "external"
causes. Warmth, air, light, moisture and nourishment, are undoubtedly
necessary factors in the process of growth, but they are only the
conditions which render it possible, and not the causes which produce
it. The latter are to be found in the individual organism itself. The
conditions may be ever so favorable and well-adapted for growth, still
the organism will not develop unless it bear within itself the power to
do so. On the other hand, although it is hampered and may become
abnormal, it will readily grow even in an unfavorable environment, as
long as it retains its inherent vital force. The same is very likely
true of the genealogical growth. Evolution took place in virtue of the
power inherent in the developing organisms. But only when the
environment was favorable and normal, did the evolution proceed
favorably and normally, that is, toward the perfection of the animate
kingdom.
It appears as if the internal principle of development were losing
influence and significance with Eimer; but the ulterior reason for this
is not far to seek. Whoever recognizes the validity of the internal
principle of development, eliminates chance, that stop-gap of
materialism, from evolution, and is lead at once to a supreme
Intelligence which directs evolution. As soon as it comes in sight,
however, certain persons take fright and turn aside or even turn back
in order to avoid it. This was the case with Eimer, although perhaps in
a lesser degree. This is sincerely to be deplored, since his theory
would have gained in depth if he had but done full justice to the
internal principle of development. For the same reason he seems to have
attacked Naegeli's principle of perfection, another fact which is very
much to be regretted. True, it is as anti-mechanical as it can be and
hence has gained but few adherents; but it is based on truth
nevertheless, and will some day prevail in the doctrine of Descent.
It is perfectly intelligible that the thought of "perfection" should
not have occurred to Eimer or should have slipped his memory during
his observations on butterflies. The fact however, reveals a
one-sidedness which he could have avoided. When the notion of utility
is rejected--and Eimer rejects it very emphatically in his discussions
on mimicry--it is undoubtedly difficult to arrive at the concept of a
perfecting tendency. This, however, can in no way mean that this
concept should be entirely banished from nature, even as the notion of
utility cannot be banished. Even if the coloration and design of the
wings of the butterfly do not reveal utility, other characteristics
certainly do reveal it. It is one of the fatal mistakes of Darwinism,
that it fails to recognize the possibility of dividing the characters
and qualities of organisms into two large groups, as I attempted
to do with more detail, for instance, in my "Catechism of Botany."
There I called them (p. 89) "Autochthon-morphological" and
"adaptive-morphological characters." The former reveal no relation
to utility, they are innate and distinguish the organism from other
organisms; the latter can be explained by means of certain vital
functions, hence they possess a certain utility and adapt themselves
more or less to environment. The former are permanent, the latter
changeable. Darwinians regard all the characters of organisms as
useful, physiological, and adaptive. If they have been hitherto
unable to make good this assumption, they appeal to our lack of
knowledge and console themselves with the thought that the future may
yet reveal the missing relations. The presence on plants and animals
of any autochthon-morphological characters means death to Darwinism,
because these can never be explained by means of selection and struggle
for existence.
Eimer is too much inclined towards the other extreme; he does not admit
the existence of adaptive-morphological characteristics. Viewed in this
aspect, his repudiation of mimicry may perhaps also seem somewhat harsh
and one-sided. In this narrowness of view must also be sought the
reason for his complete repudiation of Naegeli's principle of
perfection.
It is an incontrovertible fact that in the organic world there exists
an ascending scale from the imperfect to the perfect. Every organism is
indeed perfect in its own sphere and from its own point of view. But
perfection with reference to things of earth is a very relative
concept; many an organism which is perfect in itself, appears very
imperfect when compared with others. If, then, there is a gradation of
animals and plants from the lower to the higher, it is the task of the
theory of Descent to explain this gradual perfection. The crude and
aimless activity of Darwinian selection, which necessarily operates
through "chance," can never explain this perfection, which remains, as
far as selection is concerned, one of the greatest enigmas of nature.
Far from solving the enigma, selection but makes it obscurer.
If, then, one refuses to recognize a directing creative Intelligence,
whose direction produces this perfection, nothing remains but Naegeli's
principle of perfection. The outer world with its influences can
certainly not produce perfection, hence this power must lie within the
organism itself. But when one has once brought himself to accept an
immanent principle of development, it surely cannot be difficult to
take the next step and ascribe to it the tendency towards perfection.
That Eimer does not take this step, is, to my mind, a mistake, which
must be attributed to his one-sidedness, which, in turn, results from
the fact that he generalizes too arbitrarily his observations on
butterflies and the conclusions which he draws from them. Animals and
plants certainly possess many characteristics which cannot be explained
by means of his theory alone. The conclusion will probably be finally
arrived at, that nature is inexhaustible and many-sided, even in the
lines on which it proceeds to attain this or that end.
One thing, however, of primary importance is evident from the
investigations of Eimer, namely the proof that the same lines of
development may be entered upon from entirely different
starting-points, and that the number of these lines is limited. This
fact is of importance because it enjoins more caution in arguing from
uniformity of development to family-relation, than has been usually
employed since the days of Darwin. The method commonly employed is
undoubtedly very convenient, but is somewhat liable to be misleading.
Hence, if one wishes to establish the genealogical relationship of
forms, nothing remains but to set out on the laborious path of studying
the development of both; and even then it remains questionable whether
the truth will be arrived at. However, he who concludes to relationship
from a comparison of developed forms, is much less likely to arrive at
the truth.
In one point Eimer concedes too much to Darwinism, in the matter of the
famous fundamental principle of biogenesis, according to which an
organism is said to repeat in its individual development the whole
series of its progenitors. Although he does not enter upon a
discussion of the principle, it is evident from one passage that he
accepts it. One is inclined to think that his careful observations and
experiments should have convinced him of the contrary. It appears to
me, at least, that the abundant materials of his observations bear
evidence radically opposed to the principle. During late years, the
antagonism to it has been on the increase, and the day is not very
distant when it shall have passed into history. It would certainly be
a laudable undertaking to enter upon a thorough investigation of the
actual basis of the principle.