the variations with which it works, is removed by the apprehension that a
germinal selection exists. Natural selection is not compelled to wait until
"chance" presents the favorable variations, but supposing merely that the
groundwork for favorable variations is present in the transforming species,
that is, supposing merely that in the constitutional basis of the part to
be changed are contained components which render favorable variations
possible by a change of their numerical ratio, then those variations _must_
occur, for the reason that quantitative fluctuations are always happening,
and they must also be augmented as soon as personal selection intervenes
and permanently holds over them her protecting hand. Not only is the
marvelous _certainty and exactitude_ with which adaptation has operated in
so many individual cases, rendered intelligible in this manner, but what is
more difficult, we are able to understand the _simultaneity_ of numerous
and totally different modifications of the most diverse parts co-operant
towards some collective end, such as we see so frequently occur, {62} for
example, in the simultaneous rise of instincts and protective similarities,
or in the harmonious and simultaneous augmentation of two co-operant but
independent organs, as of the eye and of the centre of vision, or of the
nerve and its muscle, etc.
The "secret law," of which Wolff prophetically speaks in his criticism of
selection, is in all likelihood naught else than germinal selection. This
it is that brings it about that the necessary variations are always
present, that symmetrical parts, for example, the two eyes, usually vary
alike, but under circumstances may vary differently, for example, the two
visual halves of soles; that homodynamic parts, (for instance, the
member-pairs of Arthropoda,) have frequently varied alike, and not
infrequently and in conformity with the needs of the animal, have varied
differently. It brings it about also that conversely species of quite
different fundamental constitutions occasionally vary alike, as instances
of mimicry and numerous other cases of convergence show us. As soon as
utility itself is supposed to exercise a determinative influence on the
direction of variation, we get an insight into the entire process and into
much else besides that has hitherto been regarded as a stumbling-block to
the theory of selection, and which did indeed present difficulties that for
the moment were insuperable--as, for example, the like-directed variation
of a large number of already existing similar parts, seen in the origin of
feathers from the scales of reptiles. The utility in the last-mentioned
instance consisted, not in the transformation of one or two, but of _all_
the scales; consequently the line of variation of _all_ the scales must
have been started simultaneously in the same direction. A large part of the
objections to the theory of selection {63} that have been recently brought
forward by the acutest critics, as for example by Wigand, but particularly
by Wolff,[21] find, as I believe, their refutation in this doctrine of
germinal selection. The principle extends precisely as far as utility
extends, inasmuch as it creates, not only the direction of variation for
every increase or diminution demanded by the circumstances, but also every
qualitative direction of variation attainable by changes of quantity, so
far as that is at all possible for the organism in question.
Considering also the contrary process, the degeneration of useless parts by
the cessation of selection in regard to the normal size of that part, a
clear light is shed on that whole complex system of ascending and
descending modifications which makes up most of the transformations of a
living form, and we are led to understand how the fore extremity of a
mammal can change into a fin at the same time that the _hinder_ extremity
is growing rudimentary, or how one or two toes of a hoofed animal can
continue to develop more and more powerfully, whilst the others in the same
degree grow weaker and weaker until finally they have disappeared entirely
from the germ of most of the individuals of the species.
Possibly some of that large body of inquirers, mostly paleontologists, who
till now have considered the Lamarckian principle indispensable for the
explanation of these phenomena--perhaps some, I say, will not utterly close
their eyes to the insight that germinal selection performs the same
services for the understanding of observed transformations, particularly of
{64} the degeneration of superfluous parts, that a heredity of acquired
characters would perform, without rendering necessary so violent an
assumption. I have always conceded that many transformations actually do
run parallel to the use and disuse of the parts,[22] that therefore it does
really look as if functional acquisitions of the individual life were
hereditary. But if it be found that _passively functioning parts_, that is,
parts which are not alterable during the individual life by function, obey
the same laws and also degenerate when they become useless, then we shall
scarcely be able to refuse our assent to a view which explains both cases.
It certainly cannot be the physiological function which provokes
modifications in the individual, which are then subsequently transmitted to
the germ and in this way made hereditary, if _functionless parts also
change_ when they become useless. It is precisely this _uselessness_, then,
from which the initial impulse emanates, and the primary modification is
not in the soma but in the germ.
The Lamarckians were right when they maintained that the factor for which
hitherto the name of natural selection had been exclusively reserved, viz.,
_personal_ selection, was insufficient for the explanation of the
phenomena. They were also right when they declared that panmixia in the
form in which until recently I held the theory was also insufficient to
explain the degeneration of parts that had grown useless, but they {65}
erred when they ascribed hereditary effects to the selection-processes
which are enacted among the parts of the body (Wilhelm Roux) and which are
rightly regarded as the results of functioning. And they did this,
moreover, as they themselves admit, not because the facts of heredity
directly and unmistakably required it, but because they saw no other
possibility of explaining many phenomena of transformation. I am fain to
relinquish myself to the hope that now after another explanation has been
found, a reconciliation and unification of the hostile views is not so very
distant, and that then, we can continue our work together on the newly laid
foundations.
That the application of the Malthusian principle was thoroughly justified
is now clear. _The entire process of the development of living forms is
guided by this principle._ The struggle for existence, _videlicet_, for
food and propagation, takes place at all the stages of life between all
orders of living units from the biophores recently disclosed upwards to the
elements that are accessible to direct observation, to the cells, and still
higher up, to individuals and colonies. Consequently, in all the divers
orders of biological units lying between the two extremes of biophores and
colonies, the modifications must be controlled by selective processes;
therefore, these govern every change of living forms no matter what its
significance, and bring it about that the latter fit their conditions of
life as wax does the mould; and the various stages of these processes, as
enacted between the divers orders of biological units, in all organisms not
absolutely simple, are involved in incessant and mutual interaction. The
three principal stages of selection, that of {66} _personal_ selection[23]
as it was enunciated by Darwin and Wallace, that of _histonal_ selection as
it was established by Wilhelm Roux in the form of a "struggle of the
parts," and finally that of _germinal selection_ whose existence and
efficacy I have endeavored to substantiate in this article--these are the
factors that have co-operated to maintain the forms of life in a constant
state of viability and to adapt them to their conditions of life, now
modifying them _pari passu_ with their environment, and now maintaining
them on the stage attained, when that environment is not altered.
Everything is adapted in animate nature[24] and has been from the first
beginnings of life; for adaptiveness of organisation is here equivalent to
the power to exist, and they alone have had the power to exist who have
permanently existed. _We know of only one natural principle of explanation
for this fact--that of selection {67} of the picking out of those having
the power to exist from those having the power to originate._ If there is
any solution possible to the riddle of adaptiveness to ends,--a riddle held
by former generations to be insoluble,--it can be obtained only through the
assistance of this principle of the self-regulation of the originating
organisms, and we should not turn our faces and flee at the sight of the
first difficulties that meet its application, but should look to it whether
the apparent effects of this single principle of explanation are not
founded in the imperfect application that is made of it.
If I am not mistaken the situation is as follows: We had remained standing
half way. We had applied the principle, but only to a portion of the
natural units engaged in struggle. If we apply the principle throughout we
reach a satisfactory explanation. Selection of _persons_ alone is _not
sufficient_ to explain the phenomena; _germinal_ selection must be added.
Germinal selection is the last consequence of the application of the
principle of Malthus to living nature. It is true it leads us into a
terrain which cannot be submitted directly to observation by means of our
organs of touch and by our eyes, but it shares this disadvantage in common
with all other ultimate inferences in natural science, even in the domain
of inorganic {68} nature: in the end all of them lead us into hypothetical
regions. If we are not disposed to follow here, nothing remains but to
abandon utterly the hope of explaining the adaptive character of life--a
renunciation which is not likely to gain our approval when we reflect that
by the other method is actually offered at least in principle, not only a
broad insight into the adaptation of the single forms of life to their
conditions, but also into the mode of formation of the living world as a
whole. The variety of the organised world, its transformation by adaptation
to new, and by reversed adaptation to old conditions, the inequality of the
systematic groups, the attainment of the same ends by different means, that
is, by different organisations, and a thousand and one other things assume
on this hypothesis in a certain measure an intelligible form, whilst
without it they remain lifeless facts.
And so in this case, I may say, that again doubt is the parent of all
progress. For the idea of germinal selection has its roots in the necessity
of putting something else in the place of the Lamarckian principle, after
that had been recognised as inadequate. That principle did, indeed, seem to
offer an easy explanation of many phenomena, but others stood in open
contradiction to it, and consequently that was the point at which the lever
had to be applied if we were to penetrate deeper into the phenomena in
question. For it is at the places where previous views are at variance with
facts that the divining rod of the well-seekers must thrice nod. There lie
the hidden waters of knowledge, and they will leap forth as from an
artesian well if he who bores will only drive undaunted his drill into
their depths.
* * * * *
{69}
APPENDIX.
* * * * *
I. THE REJECTION OF SELECTION.
Many years ago Semper[25] denied the power of selection to create an organ,
declaring that the organ must have previously existed before selection
could have increased and developed it. More recently Wolff[26] has
distinguished himself by the vigor with which he has attacked the "task" of
"setting aside the dogma of selection." Henry B. Orr[27] is also of opinion
that selection is not the real cause of improved organic states; he regards
it as a factor checking growth in certain directions, but not as a cause
producing growth. Likewise Yves Delage,[28] in his recent voluminous but in
many respects excellent work, regards natural selection solely as a
subordinate principle which is devoid of all power to create species (p.
391), although he grants to it certain functions, and even characterises it
{70} as "an admirable and perfectly legitimate principle" (p. 371). A more
pronounced opponent of selection, of any kind, as a principle creating
species, is the Rev. Mr. Henslow,[29] whose views we shall discuss later,
in Division VII. of this Appendix.
Finally, must be mentioned the name of Th. Eimer, as that of a pronounced
and bitter enemy of the theory of selection. I shall leave it to others to
decide whether he can properly be called an "opponent" of the principle, in
the scientific acceptance of the word. I can see in the blind railings of
the Tuebingen Professor nothing but a reiteration of the same unproved
assertions, mingled with loud praises of his own doughty performances and
captious onslaughts on every one who does not value them as highly as their
originator.[30]
The lack of confidence latterly placed in the theory of selection even by
professed adherents of the doctrine, is well shown by such remarks as the
following {71} from Emery,[31] who says: "Some pupils of Darwin have gone
beyond their master and discovered in natural selection the sole and
universal factor controlling variations. Thus there has arisen in the
natural course of things a reaction, especially on the part of those who,
while they accept evolution, will have naught to do with natural selection
or Darwinism as they call it." Emery then professes himself a Darwinian,
although not in the sense of Wallace and "other co-workers and pupils of
Darwin." For him "natural selection is a very important factor in
evolution, and in determining the direction of variation plays the highest
part; but it is far from being the only factor and is probably also not the
most efficient factor." Not the most efficient factor but plays the highest
part!
* * * * *
II. CHEMICAL SELECTION.
If we refer adaptation to selection, we have also to trace back to this
source the origin of the organic combinations which make up the various
tissues of the body and which go by the collective name of muscular,
nervous, glandular substance, etc. Lloyd Morgan has prettily likened the
vital processes to the periodic formation and discharge of explosive
substances.[32] Unstable combinations are upon the application of a {72}
stimulus suddenly disintegrated into simpler and more stable compounds;
through this disintegration they evoke what is called the function of the
disintegrating part--for example, certain changes of form (muscular
contractions) or the excretion of the disintegrated products, etc.
Now how is it possible that such unstable chemical combinations, answering
exactly to the needs of life, could have arisen in such marvellous
perfection if the _useful_ variations had not always been presented to the
ceaselessly working processes of selection? or, if the constantly
increasing adaptation to the constantly augmenting delicacy of operation of
physiological substances had depended in its last resort on _accidental_
variations? Hence, not only with regard to the "form" of organs, but also
with regard to the chemical and physiological composition of their
materials, we are referred to the constant presence of appropriate
variations.
* * * * *
III. VARIATION AND MUTATION.
I have still to add a few remarks on the subject touched on in the footnote
at page 31. The view there referred to was discussed by Professor Scott
before in an article published in the _American Journal of Science_, Vol.
XLVIII., for November, 1894, entitled "On Variations and Mutations."
Following the precedent of Waagen and Neumayr, Scott sharply discriminates
between the inconstant vacillating variations which it is supposed [?]
produce simultaneously occurring "varieties," and "mutations," or the
successively evolved _time_-variations of a phylum, which constitute the
stages of phyletic development. The facts on which this view is based are
those already {73} adduced in the text--the _Zielstrebigkeit_ (to use K. E.
von Baer's phraseology) displayed in the visible paleontological
development, the directness of advance of the modifications to a final
"goal." "The direct, unswerving way in which development proceeds, however
slowly, is not suggestive of many trials and failures in all directions
save one." And again, "The march of transformation is the resultant of
forces both internal and external which operate in a _definite manner_ upon
a changeable organism and similarly affect _large numbers of individuals_."
The two points which I have here italicised are actually the facts which
separate phylogenetic from common individual variation: the definite
_manner_ of the change, repeated again and again without modification, and
its occurrence in a _large number of individuals_.
Still the two are not solely a result of observation, deduced from
paleontological data; they are also _a consequence of the theory of
selection_, as was shown in the text. If the theory in its previous form
was unable to fulfil this requirement, it is certainly now able to do so
after germinal selection has been added, and it is not in any sense
necessary to assume a difference of _character_ between phylogenetic and
ontogenetic variations. Bateson and Scott are wrong in imagining that I ask
them "to abrogate reason" in pronouncing the "omnipotence of natural
selection." On the contrary, the theory seems to me to accord so perfectly
with the facts that we might, by reversing the process, actually construct
the facts from the theory. What other than the actual conditions could be
expected, if it is a fact that selection favors only the useful variations
and singles them out from the rest by producing them in {74} increasing
distinctness and volume with every generation, and also in an increasing
number of individuals? The mere displacement of the zero-point of useful
variations alone must produce this effect, especially when it is supported
by germinal selection. It is impossible, indeed, to see how considerable,
that is perceptible, deviations could arise at all on the path of phyletic
development if in each generation a large number of individuals always
possessed the useful, that is, the phyletic variations? In fact, by the
assumption itself, the difference between useful and less useful variations
is merely one of degree, and that a slight one.
Hence, as I before remarked at page 31, I see no reason for assuming two
kinds of hereditary variations, _distinct as to their origin_, such as
Scott and the other palaeontologists mentioned have been led to adopt,
although with the utmost caution. I believe there is only one kind of
variation proceeding from the germ, and that these germinal variations play
quite different roles according as they lie or do not lie on the path of
adaptive transformation of the species, and consequently are or are not
favored by germinal selection. To repeat what I have said in the footnote
to page 31 only a relatively small portion of the numberless individual
variations lie on the path of phyletic advancement and so mark out under
the _guidance_ of germinal selection the way of further development; and
hence it would be quite possible to distinguish continuous, _definitely
directed_ variations from such as fluctuate hither and thither with no
uniformity in the course of generations. The origin of the two is the same;
they bear in them nothing that distinguishes the one from the other, and
their success alone, that {75} is, the actual resultant phyletic
modification, permits their being known as phyletic or as vacillating
variations. Uncertain fluctuations along the path of evolution are what the
geologists would be naturally led to expect from the theory of selection,
but which they were unable to discover in the facts; it is evident,
however, that these fluctuations are not a logical consequence of the
theory of selection as that is perfected by germinal selection, and there
seems to me to be no reason now for attributing "variations" to the union
of changing hereditary tendencies, while "mutations" are ascribed to the
effect "of dynamical agencies acting long in a uniform way, and the results
controlled by natural selection."
The idea which the Grecian philosophers evolved of the thousands of
non-adaptive formations that nature brings forth by the side of adaptive
ones, and which must subsequently all perish as being unfit to live, is
certainly correct in its ultimate foundations. But it is in need of far
more radical refinement than it underwent in the hands of Empedocles, or
than it seems likely to undergo at the hands of many contemporary
inquirers. We know now that nature did not produce isolated eyes, ears,
arms, legs, and trunks, and afterwards permit them to be joined together
just as the play of the fundamental forces of love and hatred directed,
leaving the monsters to perish and granting permanent existence only to
harmonious products. Yet there is a weak echo of this conception, although
infinitely far removed from its prototype, in the question as to where all
the non-adaptive individuals are preserved that have perished in the
struggle for existence and been eliminated from development by selection?
Where, for example, are the fossil remains {76} of the rejected individuals
in the line of the Horses? Certainly they should be forthcoming in far
larger numbers than the individuals lying directly in the path of
development, for by our very assumption the latter were greatly in the
minority in every generation. Doubtless the question would be a proper one
if our eyes were sufficiently keen-sighted to assign the life-value of the
various minute differences that distinguish the "better" from the "worse"
individuals of every generation. But this is a task which we can accomplish
at best only with selective processes which are artificially directed by
ourselves, as in the case of doves and chickens, and even there only with
the utmost difficulty and only with reference to a single characteristic
and not with any species which to-day exists in the state of nature.
Picture, then, the difficulties attending such a task as applied to the
meagre fossilic bones of prehistoric species, touching which the richest
discoveries never so much as remotely approach to the actual number of
individuals that have lived together for a _single_ generation in the same
habitat. If the differences between good and bad in a single generation
were striking enough to be immediately remarked _as such_ in fossil bones,
the development of species would take place so rapidly that we could
directly witness it in living species.
* * * * *
IV. REMARKS ON THE HISTORY OF DEFINITELY DIRECTED VARIATIONS.
As to the attempt here made to apply the selective process to the elements
of the germinal substance (the idioplasm) and thus to acquire a foothold
for definitely directed variation not blind in its tendency but {77}
proceeding in the direction of adaptive growth, it is remarkable that the
same was not made long ago by some one or other of the many who have
thought and written on selection and evolution.