On germinal selection as a source of definite variation

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ON

GERMINAL SELECTION

AS A

SOURCE OF DEFINITE VARIATION

BY

AUGUST WEISMANN
TRANSLATED FROM THE GERMAN BY
THOMAS J. McCORMACK

1995

SECOND EDITION

CHICAGO
THE OPEN COURT PUBLISHING COMPANY
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Kecan Paut, Trencu, TRUBNER & Co., Lrp.
1902

CopyRIGHT BY

THe Open Court PusLIsHING Co.

1896

PREFACE.

The present paper was read in the first general
meeting of the International Congress of Zodlogists at
Leyden on September 16, 1895. Several points, which
for reasons of brevity were omitted when the paper
was read, have been re-embodied in the text, and an
Appendix has been added where a number of topics
receive fuller treatment than could well be accorded
to them in a lecture. The address was first printed in
The Monist for January, 1896, and afterwards in a
German pamphlet.

The basal idea of the essay—the existence of Ger-
minal Selection—was propounded by me some time
since,t but it is here for the first time fully set forth
and tentatively shown to be the necessary complement
of the process of selection. Knowing this factor, we
remove, it seems to me, the patent contradiction of
the assumption that the general fitness of organisms,
or the adaptations necessary to their existence, are
produced by accidental variations—a contradiction
which formed a serious stumbling-block to the theory
of selection. Though still assuming that the primary
variations are “accidental,” I yet hope to have demon-
strated that an interior mechanism exists which com-
pels them. to go on increasing in a definite direction,
the moment selection. intervenes. Definitely directed

1 Neue Gedanken zur Vererbungsfrage, eine Antwort an
Herbert Spencer. Jena. 1895.
3

4 PREFACE.

variation exists, but not predestined _ variation, run-
ning on independently of the life-conditions of the
organism, as_Naegeli, to mention the most extreme
advocate of this doctrine, has assumed ; on the con-
trary, the, variation is such as is elicited and con-
trolled by those conditions themselves, though indi-
rectly.

In basing my proof of the doctrine of Germinal Se-
lection on the fundamental conceptions of my theory of
heredity, a few words of justification are necessary,
. owing to the fact that the last-mentioned theory has
been widely and severely assailed since its first emer-
gence into light and even repudiated as absolutely
futile and erroneous.

In the first place, many critics have characterised it
as a “pure creation of the imagination.” And to a
certain extent it is such, as every theory is. But is
it on that account necessarily wrong? Can not its
fundamental ideas still be quite correct, and it itself
therefore perfectly justified as a means of further
progress?

Surely my critics cannot be ignorant of the promi-
nent part which imagination has recently played in
the exactest of all natural sciences—physics? Are
they unaware that the English physicist Maxwell
“constructed from liquid vortices and friction-pulleys
enclosed in cells with elastic walls, a wonderful mech-
anism, which served as a mechanical model for electro-
magnetism”? He hoped “that further research in
the domain of theoretical electricity would be pro-
moted rather than hindered by such mechanical fic-

1See Boltzmann, Methoden der theor. Physik, Munich,
1892. (In the Catalogue of the Mathematical Exhibit.)

PREFACE. 5

tions.” And so it actually happened, for Maxwell
found by means of them “the very equations, whose
singular and almost incomprehensible power Hertz
has so beautifully portrayed in his lecture on the reld-
tions between light and electricity.” “Maxwell’s for-
mule were the direct outcome of his mechanical
models.” “These ideal mechanisms’—so relates Boltz-
mann in the same interesting essay—‘were at first
widely ridiculed, but gradually the new ideas worked
their way into all fields. They were themselves more
convenient than the old hypotheses. For the latter
could be maintained only in the event of everything’s
proceeding smoothly; whereas now little inconsist-
encies were fraught with no peril, for no one can take’
amiss a slight hitch in a mere analogy.—Ultimately
Maxwell’s ideas were philosophically generalised as
the theory that all knowledge consists in the dis-
closure of analogies.”

But not only does it seem that there is little appre-
ciation among biologists for the scientific import of
imagination, they also appear to have little sense for
the significance of theory. It is a favorite attitude
nowadays to look upon theory as a sort of superfluous
ballast, as a worthless survival from the epoch of
decrepit ‘nature-philosophies.” People pronounce
with pride the miscomprehended utterance of New-
ton, Hypotheses non fingo, and place the value of the
slightest new fact infinitely higher than that of “the
most beautiful theory.” And yet theory originally

10Of late this saying of Newton’s is frequently quoted as
if Newton were a downright contemner of scientific hypothe-
ses. But if we read the passage in question in its original
context, we shall discover that his renunciation of hypotheses
referred solely to a definite case, viz. to that of universal

6 PREFACE.

fashions science out of facts and is the indispensable
precondition of every important scientific advance.

Heinrich Hertz, the discoverer of electric undula-
tions, had the same thought in mind when he said:
“We form inward representations or constructs of
outward objects, so constituted that the results that
follow logically and necessarily from the constructs
are in turn always constructs of the results flowing
naturally and necessarily from the objects.” “These
constructs or mental images copied after familiar ob-
jects possessed of familiar properties, so constituted
that from their manipulation effects result similar to
those which we observe in the objects to be explained.
Experience teaches us that the requirements here
made can be fulfilled and that consequently such ‘cor-
respondences’ between reality and the supposed images
[or, as Hertz says, between nature and mind] actually
exist. Having succeeded in extracting from the ac-
cumulated experience of the past, representative
images or constructs fulfilling all these necessary re-
quirements, we can then reproduce by them in a short
space of time, as we might by models, results that
in the outward world require a long space of time for
their actualisation or can be produced only through
our personal intervention,” etc.

ee

gravitation, of whose character Newton could form no con-
ception and hence was unwilling to construct hypotheses
concerning it. Indeed, such a wholesale repudiation of hy-
potheses is antecedently incredible on the part of the inventor
of the emission-theory of light, in which, to speak of only
one daring conjecture, “fits” were ascribed to the luminous
particles. Compare Newton, Philosophiae Naturalis Prin-
cipia Mathematica, second edition, 1714, page 484.

1H. Hertz, Die Principien der Mechanik.

PREFACE. 7

Such representative models, or constructs, now, in
my theory of heredity, are the determinants, which
may be conceived as indefinitely fashioned packages
of units (biophores) which are set into activity by
definite impressions and put a distinctive stamp upon
some small part of the organism, on some cell or
group of cells, evoking definite phenomena somewhat
as a piece of fireworks when lighted produces a bril-
liant sun, a shower of sparks, or the glowing characters
of a name.

The ids, also, are such representative models, and
may be “compared to a definitely ordered but variously
compounded aggregate of fireworks, in which the
single pieces are so connected as to go off in fixed
succession and to produce a definite resultant phenom-
enon like a complete inscription surrounded by a hail
of fire and glowing spheres.

Owing to the greater complexity of the phenomena
in biology we can never hope to reach the same dis-
tinctness in our constructs and models as in physics,
and the attempt to derive from them mathematical
formule by the independent development of which
research could be continued, would at present be
utterly fruitless. In the meantime it seems preferable
to have some sort of adequate model to which the
imagination can always resort and with which it can
easily operate, rather than to have to revert, in con-
sidering every special problem of heredity, to the
mutual actions of the molecules of living substance
and outward agents—processes which we know only
in their roughest outlines. Or is any one presumptu-
ous enough to believe we can infer from our slight
knowledge of the chemical and physical constitution
of the germs of a trout and a salmon the real cause

8 PREFACE.

of the one’s becoming a trout and of the other’s becom-
ing a salmon?

The fact is, we can make no show of accounting for
the complex phenomena of heredity with mere material
units; we can never reach these phenomena from
below, but must begin farther up and make the as-
sumption of vital units and hereditary units, if there is
to be any advance in this field.

It is undoubtedly a splendid aim which the newly
founded science of developmental mechanics has set
itself of laying bare the entire causal line leading from
the egg to the finished organism; yet, however much.
we may wish to see the success of this plan realised,
we cannot disguise the fact that little or nothing is
to be accomplished by it in the settlement of the
problems of heredity. It is impossible to suspend the
study of heredity until this mechanics is completed,
and even if we could it would help us little, for the
riddles of heredity are not concealed in the ontogenesis
of types, or, to give an example, in the developmental
history of man as a race, but in the ontogenesis of
individuals, in that of a definite and particular man.
This last ontogenesis exhibits the phenomena of varia-
tion, of reversion, of the predominance of the one or
the other parent, etc., and no one is likely to believe
that inductive evolutional inquiry alone will ever afford
us knowledge of these minute and delicate processes,
which, in their bearing on the total resultant devel-
opment, phylogenesis, are after all the most important
of all.

_There is, accordingly, no choice left. If we are
really bent on scientifically investigating the question
of heredity, we are obliged perforce to form from the
observed facts of heredity a highly detailed and elab-

PREFACE. 9

orate theory, on the basis of which we can propound
new questions, which will give rise in turn to new
facts, and thus will exercise a retroactive influence on
the theory, improving and transforming it.

This is precisely what I have sought to accomplish
by my theory of Germ-plasm, as I stated in the Preface
to the book bearing that name. It was never intended
as a theory of life, nor, indeed, primarily, as a theory
of evolution, but first and above all as a theory of
heredity. I cannot understand, therefore, the animad-
version, that my theory in no way furthers our insight
into the mechanics of development. That is not its
purpose; in fact, it takes the ultimate physical and
chemical processes which make up the vital processes
for granted; and inevitably it is constrained to do
so. Its aim is to put into our hands a serviceable:
formula by means of which we can go on working
in the field of heredity at any rate, and, if I am not
mistaken, also in that of evolution. To me, at least,
the newest results of developmental mechanics do
not seem so widely at variance with the theory of
determinants as might appear at first sight; so far
as I can see, they can be quite readily made to har-
monise with the theory, provided only the initial stage
of the disintegration of the germ-plasm in the deter-
minant groups be not invariably placed at the begin-
ning of the process of segmentation, but be transferred
according to circumstances to a subsequent period.
The exact state of things cannot as yet be determined,
so long as the mass of facts is still in constant flux.

In any: event I still hold fast to the hope which I
expressed in the Preface to my Germ-plasm, that de-
spite the unavoidable uncertainties in its foundation
my theory would yet prove more than a mere work

10 PREFACE.

of imagination, and that the future would find in it
some durable points which would outlive the muta-
tions of opinion. It is possible that one of these dura-
ble gains is my much impugned idea of determinants,
and in fact not only will the present essay be made
to rest on this idea, but it will also defend it on new
grounds, although primarily only as a representation
of something which we do not as yet exactly know, but
which still exists and on which we can reckon, leaving
it to the future to decide the greater or less resem-
blance of our hypothetical construct to nature.

The real aim of the present essay is to rehabilitate
the principle of selection, If I should succeed in rein-
stating this principle in its emperilled rights, it would
be a source of extreme satisfaction to me; for I am
so thoroughly convinced of its indispensability as to
believe that its demolition would be synonymous with
the renunciation of all inquiry concerning the causal
relation of vital phenomena. If we could understand
the adaptations of nature, whose number is infinite;
only upon the assumption of a teleological principle,
then, I think, there would be little inducement to
trouble ourselves about the causal connexion of the
stages of ontogenesis, for no good reason would
exist for excluding teleological principles from this
field. Their introduction, however, means the ruin of

science. Aucust WEISMANN.
Frerpurc, Nov. 18, 1895.

GERMINAL SELECTION.

Numerous and varied are the objections that have
been advanced against the theory of selection since it
was first enunciated by Darwin and Wallace—from
the unreasoning strictures of Richard Owen and the
acute and thoughtful criticisms of Albert Wigand and
Nageli to the opposition of our own day, which con-
tends that selection cannot create but only reject, and
which fails to see that precisely through this rejection
its creative efficacy is asserted. The champions of this
view are for discovering the motive forces of evolution
in the Jaws that govern organisms—as if the norm
according to which an event happens were the event
itself, as if the rails which determine the direction
of a train could supplant the locomotive. Of course,
from every form of life there proceeds only a definite,
though extremely large, number of tracks, the possi-
ble variations, whilst between them lie stretches with-
out tracks, the impossible variations, on which locomo-
tion is impossible. But the actual travelling of a track
is not performed by the track, but by the locomotive,
and on the other hand, the choice of a track, the
decision whether the destination of the train shall be
Berlin or Paris, is not made by the locomotive, the
cause of the variation, but by the driver of the loco-
motive, who directs the engine on the right track. In
the theory of selection the engine-driver is repre-
sented by utility, for with utility rests the decision

11

12 GERMINAL SELECTION.

as to what particular variational track shall be trav-

“elled. The cogency, the irresistible cogency, as I take
it, of the principle of selection is precisely its capacity —
of explaining why fit structures always arise, and
that certainly is the great problem of life. Not the
fact of change, but the manner of the change, whereby
all things are maintained capable of life and existence,
is the pressing question.

It is, therefore, a very remarkable fact, and one de-
serving of consideration, that to-day (1895), after
science has been in possession of this principle for
something over thirty years and during this time has
steadily and zealously busied itself with its critical
elaboration and with the exact determination of its
scope, that now the estimation in which it is held
should apparently be on the decrease. It would be
easy to enumerate a long list of living writers who
assign to it a subordinate part only in evolution, or
none at all. One of our youngest biologists speaks
without ado of the “pretensions of the refuted Dar-
winian theory, so called,”? and one of the oldest and
most talented inquirers of our time, a pioneer in the
theory of evolution, who, unfortunately, is now gone,
to his rest, Thomas Huxley, implicitly yet distinctly
intimated a doubt regarding the principle of selection
when he said: “Even if the Darwinian hypothesis
were swept away, evolution would still stand where
it is.” Therefore, he, too, regarded it as not impossible
that this hypothesis should disappear from among

1Hans Driesch, Die Biologie als selbststindige Grund-
wissenschaft, Leipsic, 1893, p. 31, footnote. The sentence
reads: “An examination of the pretensions of the refuted

Darwinian theory, so called, would be an affront to our
readers.”

GERMINAL SELECTION. 13

the great explanatory principles by which we seek
to approach nearer to the secrets of nature.

I am not of that opinion. I see in the growth of
doubts regarding the principle of selection and in
the pronounced and frequently bitter opposition which
it encounters, a transient depression only of the wave
of opinion, in which every scientific theory must de-
scend after having been exalted, here perhaps with
undue swiftness, to the highest pitch of recognition.
It is the natural reaction from its overestimation,
which is now followed by an equally exaggerated
underestimation. The principle of selection was not
overrated in the sense of ascribing to it too much
explanatory efficacy, or of extending too far its sphere
of operation, but in the sense that naturalists imag-
ined that they perfectly understood its ways of work-
ing and had a distinct comprehension of its factors,
which was not so. On the contrary, the deeper they
‘penetrated into its workings the clearer it appeared
that something was lacking, that the action of the
-principle, though upon the whole clear and representa-
-ble, yet when carefully looked into encountered numer-
ous. difficulties, which were formidable, for the reason
that we were unsuccessful in tracing out the actual
details of the individual process, and, therefore, in
fixing the phenomenon as it actually occurred. We
can state in no single case how great a variation must
be to have selective value, nor how frequently it must
occur to acquire stability. We do not know when
and whether a desired useful variation really occurs,
nor on what its appearance depends; and we have no
means of ascertaining the space of time required for
the fulfilment of the selective processes of nature, and
hence cannot calculate the exact number of such proc-

14 GERMINAL SELECTION.

esses that do and can take place at the same time in
the same species. Yet all this is necessary if we wish
to follow out the precise details of a given case.

But perhaps the most discouraging circumstance of
all is, that in scarcely a single actual instance in
nature can we assert whether an observed variation is
useful or not—a drawback that I distinctly pointed out
some time ago.1. Nor is there much hope of better-
ment in this respect, for think how impossible it would
be for us to observe all the individuals of a species in
all their acts of life, be their habitat ever so limited—
and to observe all this with a precision enabling us
to say that this or that variation possessed selective
value, that is, was a decisive factor in determining the
existence of the species.

In many cases we can reach at least a probable in-
ference, and say, for example, that the great fecundity
of the frog is a property having selective value, basing
our inference on the observation that in spite of this
fertility the frogs of a given district do not increase.

But even such inferences ‘offer only a modicum of
certainty. For who can say precisely how large this
number is? Or whether it is on the increase or on
the decrease? And besides, the exact degree of the
fecundity of these arumals is far from being known.
Rigorously viewed, we can only say that great fe-
cundity must be advantageous to a much-persecuted
animal.

And thus it is everywhere. Even in the most in-
dubitable cases of adaptation, as, for instance, in that
of the striking protective coloring of many butterflies,

1Die Allmacht der Naturziichtung. A Reply to Herbert

Spencer. Jena, 1893, p. 27 et seq. [Also in the Contemporary
Review for September, 1893.]

GERMINAL SELECTION. 15

the sole ground of inference that the species upon
the whole is adequately adapted to its conditions of
life, is the simple fact that the species is, to all appear-
ances, preserved undiminished, and the inference is not
at all permissible that just this protective coloring has
selective value for the species, that is, that if it were
lacking, the species would necessarily have perished.
It is not inconceivable that in many species to-day
these colorings are actually unnecessary for the pres-
ervation of the species, that they formerly were, but
that now the enemies which preyed on the resting but-
terflies have grown scarce or have died out entirely,
and that the protective coloring will continue to exist
by the law of inertia’ only for a short while till pan-
mixia or new adaptations shall modify it.
Discouraging, therefore, as it may be, that the con-
trol of nature in her minutest details is here gainsaid
us, yet it were equivalent to sacrificing the gold to
the dross, if simply from our inability to follow out
the details of the individual case we should renounce
altogether the principle of selection, or should proclaim
it as only subsidiary, on the ground that we believe
the protective coloring of the butterfly is not a pro-
tective coloring, but a combination of colors inevitably
resulting from internal causes. The protective color-
ing remains a protective coloring whether at the time
in question it is or is not necessary for the species; and
it arose as protective coloring—arose not because it
was a constitutional necessity of the animal’s organism
that here a red and there a white, black, or yellow
spot should be produced, but because it was advan-

1 That is, by the law of exceedingly slow retrogression of
superfluous characters, which may be designated the law of
organic inertia.

16 GERMINAL SELECTION.

tageous, because it was necessary for the animal.
There is only one explanation possible for such patent

adaptations and that is selection. What is more, no

other natural way of ‘their originating is conceivable,
for we have no right to assume teleological forces in
the domain of natural phenomena.

~T have selected the example of the butterfly’s wing,
not solely because it is so widely. known, but because
it is so exceedingly instructive, because we are still
able to learn so much from it. It has been frequently
‘asserted that the color-patterns of the butterfly’s wings
have originated from internal causes, independently
of selection and conformably to inward laws of evo-
lution. Eimer has attempted to prove this assertion
by establishing in a division of the genus Papilio the
fact that the species there admit of arrangement in

series according to affinity of design. But is a proof _

that the markings are modified in definite directions
-during the course of the species’s development equiv-
alent to a definite statement as to the causes that have
produced these gradual transformations? Or, is our
present inability to determine with exactness the bio-
logical significance of these markings and their modi-
fications, a proof that the same have no significance
whatever? On the contrary, I believe it can be clearly
proved that the wing of the butterfly is a tablet on
which nature has inscribed everything she has deemed
advantageous to the preservation and welfare of her
creatures, and nothing else; or, to abandon the sim-
ile, that these color-patterns have not proceeded from
inward evolutional forces, but are the result of selec-
tion. At least in all places where we do understand _
their biological significance these patterns are consti-

tuted and distributed over the wing exactly as utility © ~

would require.

GERMINAL SELECTION. 17

I do not pledge myself, of course, to give an expla-
nation of every spot and every line on a wing. The
inscription is often a very complicated one, dating
from remote. and widely separated ages; for every
single existing species has inherited the patterns of
its ancestral species and that again the patterns of
a still older species. Even at its origin, therefore,
the wing was far from being a tabula rasa, but was
a closely written and fully covered sheet, on which
there was no room for new writing until a portion of
the old had been effaced. But other parts were pre-
served, or only slightly movified, and thus in many
cases gradually arose designs of almost undecipherable
complexity.

I should be far from maintaining that the markings
arose unconformably to law. Here, as elsewhere, the
dominance of law is certain. But I take it, that the
laws involved here, that is, the physiological conditions
of the variation, are without exception subservient to
the ends of a higher power—utility; and that it is util-
ity primarily that determines the kind of colors, spots,
streaks and bands that shall originate, as also their
place and mode of disposition. The laws come into
consideration only to the extent of conditioning the
quality of the constructive materials—the variations,
out of which selection fashions the designs in ques-
tion. And this also is subject to important restric-
tions, as will appear in the sequel.

The meaning of formative laws here is that definite
spots on the surfaces of the wings are linked together
in such a manner by inner, invisible bonds, as to
represent the same spots or streaks, so that we can
predict from the appearance of a point at one spot the
appearance of another similar point at another, and

18 GERMINAL SELECTION.

so on. It is an undoubted fact that such relations
exist, that. the markings frequently exhibit a certain
symmetry, that—to use the words of the most recent
observer on this subject, Bateson’—a meristic repre-
sentation of equivalent design-elements occurs. But
I believe we should be very cautious in deducing laws
from these facts, because all the rules traceable in the
markings apply only to small groups of forms and are
never comprehensive nor decisive for the entire class
or even for the single sub-class of diurnal butterflies,
in fact, often not so for a whole genus. All this
points to special causes operative only within this
group.

If internal laws controlled the marking on butter-
' flies’ wings, we should expect that some general rule
could be established, requiring that the upper and
under surfaces of the wings should be alike, or that
they should be different, or that the fore wings should
be colored the same as or differently from the hind
wings, etc. But in reality all possible kinds of com-
binations occur simultaneously, and no rule holds
throughout. Or, it might be supposed that bright
colors should occur only on the upper surface or only
on the under surface, or on the fore wings or only
on the hind wings. But the fact is, they occur indis-
criminately, now here, now there, and no one method
of appearance is uniform throughout all the species.
But the fitness of the various distributions of colors is
apparent, and the moment we apply the principle of
utility we know why in the diurnal butterflies the
upper surface alone is usually variegated and the under
surface protectively colored, or why in the nocturnal

1 Materials for the Study of Variation with Especial Re-
gard to Discontinuity in the Origin of Species. London, 1895.

GERMINAL SELECTION. 1g

butterflies the fore wings have the appearance of
bark, of old wood, or of a leaf, whilst the hind wings,
which are covered while resting, alone are brilliantly
colored. On this theory we also understand the excep-
tions to these rules. We comprehend why Danaids,
Heliconids, Euploids, and Acracids, in fact all diurnal
butterflies, offensive to the taste and smell, are mostly
brightly marked and equally so on both surfaces,
whilst all species not thus exempt from persecution
have the protective coloring on the under surface
and are frequently quite differently colored there
from what they are on the upper.

In any event, the supposed formative laws are not
obligatory. Dispensations from them can be issued
and are issued whenever utility requires it. Indeed,
so far may these transgressions of the law extend,
that in the very midst of the diurnal butterflies is
found a genus, the South American Ageronia, which,
like the nocturnal butterfly, shows on the entire upper
surface of both wings a pronounced bark-coloration,
and concerning which we also know (and in this re-
spect it is an isolated genus and differs from almost
all other diurnal butterflies), that it spreads out its
wings when at rest like the nocturnal butterfly, and
does not close them above it as its relatives do. There-
fore, entirely apart from cases of mimicry, which after
all constitute the strongest proof, the facts here cited
are alone sufficient to remove all doubt that not inner
necessities or so-called formative laws have painted the
surface of the butterflies’ wings, but that the condi-
tions of life have wielded the brush.

This becomes more apparent on considering the
details. I have remarked that the usually striking
colorations of exempt butterflies, as of the Heliconids,

20 GERMINAL SELECTION.

are the same on both the upper and the lower surfaces
of the wings. Possibly the expression of a law might
be seen in this fact, and it might be said, the coloration
of the Heliconids runs through from the upper to
the under surface. But among numerous imitators
of the Heliconids is the genus Protogonius, which
has the coloration of the Heliconids on its upper sur-
face, but on its lower exhibits a magnificent leaf-
design. During flight it appears to be a Heliconid and
at rest a leaf. How is it possible that two such totally
different types of coloration should be combined in
a single species, if any sort of inner rigorous necessity
existed, regulating the coloration of the two wing-
surfaces? Now, although we are unable to prove
that the Protogonius species would have perished
unless they possessed this duplex coloration, yet it
would be nothing less than intellectual blindness to
deny that the butterflies in question are effectively
protected, both at rest and during flight, that their
colorations are adaptive. We do not know their prim-
itive history, but we shall hardly go astray if we
assume that the ancestors of the Protogonius species
were forest-butterflies and already possessed an under
surface resembling a leaf. By this device they were
protected when at rest. Afterwards, when this pro-
tection was no longer sufficient, they acquired on their
upper surface the coloration of the exempt species
with which they most harmonised in abode, habits of
life, and outward appearance.

At the same time it is explained why these butter-
flies did not acquire the coloration of the Heliconids
on the under surface. The reason is, that in the atti-

tude of repose they were already protected, and that
in an admirable manner.

GERMINAL SELECTION. 21

That exempt diurnal butterflies should be colored
on the upper and under surfaces alike, and should
never resemble in the attitude of repose their ordinary
surroundings, is intelligible when we reflect that it is
a much greater protection to be despised when dis-
covered than to be well, or very well, but never abso-
lutely, protected from discovery.

It has been so often reiterated that diurnal butter-
flies, as a rule, are protectively colored on the under
surfaces, that one has some misgivings in stating the
fact again. And yet the least of those who hold this
to be a trivial commonplace know how strongly its
implications militate against the inner motive and
formative forces of the organism, which are ever
and anon appealed to. No less than sixty-two genera
are counted today in the family of diurnal butter-
flies known as the Nymphalide. Of these by far the
largest majority are sympathetically colored under-
neath, that is, they show in the posture of rest the
colorings of their usual environment. In a large
number of the species belonging to this group the
entire surface of the hind wings possesses such a
sympathetic coloration, as does also the distant apex
of the fore wings. Why? The reason is obvious.
This part only of the fore wing is visible in the atti-
tude of repose. Here, then,—as a zealous opponent
of the theory of selection once exclaimed,—there is
undoubted “correlation” between the coloring of the
surface of the hind wing and of the apex of the fore
wing. Correlation is unquestionably a fine word, but
in the present instance it contributes nothing to the
understanding of the problem, for there are near rela-
tives and often species of the same genera in which
this correlation is not restricted to the apex of the

22 GERMINAL SELECTION.

fore wings, but extends to a third or even more of
their wings, and these species are also in the habit of
drawing back their wings less completely in the state
of rest, thus rendering a larger portion of them vis-
ible. There are species, too, like the forest-butterflies
of South America just mentioned, the Protogonius,
Anza, Kallima species, etc., which have nearly the
whole of the under surfaces of their fore wings
marked according to the same pattern with their hind
wings, and these butterflies when at rest hold their
fore wings free and uncovered ‘by their hind wings.
Where are the formative laws in such cases?

Or, perhaps some one will say: “The covering by
the hind wings hinders the formation of scales on the
wing, or impedes the formation of the colors in the
scales.” Such a person should examine one of these
species. He will find that the scales are just as dense
on the covered as on the uncovered surface of the
wing, and in many species, for example, in Katagram-
ma, the scales of the covered surface are colored most
brilliantly of all.

But the facts are still more irresistible, when we con-
sider special adaptations ; for example, the imitation of
leaves, which is so often cited. It is to be noted, first,
that this sort of imitation is by no means restricted
to a few genera, still less to a few species. All the
numerous species of the genus Anza, which are dis-
tributed over the forests of tropical South America,
exhibit this imitation in pronounced and varied forms,
as do likewise the American genera Hypna and Sider-
one, the Asiatic Symphaedra, the African Salamis,
Eurypheme, etc. I have observed fifty-three genera
in which it is present in one, several, or in many
species, but there are many others,

GERMINAL SELECTION. 23

These genera, now, are by no means all so nearly
allied that they could have inherited the leaf-markings
from a common ancestral form. They belong to dif-
ferent continents and have probably for the most part
acquired their protective colorings themselves. But
one resemblance they have in common—they are all
forest-butterfies. Now what is it that has put so
many genera of forest-butterflies and no others into
positions where they could acquire this .resemblance
to leaves? Was it directive formative laws? If we
closely examine the markings by which the similarity
of the leaf is determined, we shall find, for example, in
Kallima Inachis, and Parallecta, the Indian leaf-butter-
flies, that the leaf-markings are executed in absolute
independence of the other uniformities governing the
wing.

From the tail of the wing to the apex of the fore
wings runs with a beautiful curvature a thick, doubly-
contoured dark line accompanied by a brighter one,
representing the midrib of the leaf. This line cuts
the “veins” and the “cells” of the wing in the most
disregardful fashion, here in acute and here in obtuse
angles, and in absolute independence of the regular
system of divisions of the wing, which should as-
suredly be the expression of the “formative law of the
wing,” if that were the product of an internal directive
principle. But leaving this last question aside, this
much is certain with regard to the markings, that they
are dependent, not on an internal, but on an external
directive power.
~ Should any one be still unconvinced by the evidence
we have adduced, let him give the leaf-markings a
closer inspection. He will find that the midrib is com-
posed of two pieces of which the one belongs to the

24 GERMINAL SELECTION.

hind wing and the other to the fore wing, and that
the two fit each other exactly when the butterfly is in
the attitude of repose, but not otherwise. Now these
two pieces of the leaf-rib do not begin on correspond-
ing spots of the two wings, but on absolutely non-
identical spots. And the same is also true of the
lines which represent the lateral ribs of the leaf.
These lines proceed in acute angles from the rib; to the
right and to the left in the same angle, those of the
same side parallel with each other. Here, too, no
relation is noticeable between the parts of the wings
over which the lines pass. The venation of the wing
is utterly ignored by the leaf-markings, and its sur-
face is treated as a tabula rasa upon which anything
conceivable can be drawn. In other words, we are
presented here with a bilaterally symmetrical figure
engraved on a surface which is essentially radially
symmetrical in its divisions. ~

I lay unusual stress upon this point because it shows
that we are dealing here with one of those cases which
cannot be explained by mechanical, that is, by natural
means, unless natural selection actually exists and is
actually competent to create new properties; for the
Lamarckian principle is excluded here ab initio, see-
ing that we are dealing with a formation which is
only passive in its effects; the leaf-markings are ef-
fectual simply by their existence and not by any func-
tion which they perform; they are present in flight
as well as at rest, during the absence of danger, as well
as during the approach of an enemy.

Nor are we helped here by the Bees of purely
internal motive forces, which Nageli, Askenasy, and
others have put forward as supplying a mechanical
force of evolution. It is impossible to regard the co-

GERMINAL SELECTION. 25

incidence of an Indian butterfly with the leaf of a
tree now growing in an Indian forest as fortuitous,
as a lusus nature. Assuming this seemingly mechan-
ical force, therefore, we should be led back inevitably
to a teleological principle which produces adaptive
characters and which must have deposited the direc-
tive principle in the very first germ of terrestrial or-
ganisms, so that after untold ages at a definite time
and place the illusive leaf-markings should be devel-
oped. The assumption of pre-established harmony
between the evolution of the ancestral line of the tree
with its pre-figurative leaf, and that of the butterfly
with its imitating wing, is absolutely necessary here
—a fact which I pointed out many ‘years ago,’ but
which is constantly forgotten by the promulgators of
the theory of internal evolutionary forces.

For the present I leave out of consideration alto-
gether the question as to the conceivable extent of the
sphere of operation of natural selection; I am primar-
ily concerned only with elucidating the process of se-
lection itself, wholly irrespective of the comprehensive--
ness or limitedness of its sphere of action. For this
purpose it is sufficient to show, as I have just done,
that cases exist wherein all natural explanations ex- -
cept that of selection fail us. But let us now see
how far the principle of selection will carry us in the
explanation of such cases—natural selection, I mean,
as it was formulated by Darwin and Wallace.

There can be no doubt but the leaf-markings readily
admit of production in this manner, slowly and with
a gradual but constant increase of fidelity, provided
a single condition is fulfilled: the occurrence of the

1Studien zur Descendenstheorie, Leipsic, 1876. Vol. II,
pp. 295 and 322.

26 GERMINAL SELECTION.

right variations at the right place. But just here, it
would seem, is the insurmountable barrier to the ex-
planatory power of our principle, for who, or what,
is to be our guarantee that dark scales shall appear at
the exact spots on the wing where the midrib of the
leaf must grow? And that later dark scales shall
appear at the exact spots to which the midrib must be
prolonged? And that still later such dark spots shall-
appear at the places whence the lateral ribs start, and
that here also a definite acute angle shall be accurately
preserved, and the mutual distances of the lateral ribs
shall be alike and their courses parallel? And that
the prolongation of the median rib from the hind
wing to the fore wing shall be extended exactly to
that spot where the fore wing is not covered by the
hind wing in the attitude of repose? And so on.

-If I could go more minutely into this matter, I
should attempt to prove that the markings, as I have
just assumed, have not arisen suddenly, but were per-
fected very, very gradually; that in one species they
began on the fore wing and in another on the hind
wing; and that in many they never until recently pro-
ceeded beyond one wing, in other species they went
only a little way, and in only a few did they spread
over the entire surface of both wings.

That these markings advanced slowly and gradually,
but with marvelous accuracy, is no mere conjecture.
But it follows that the right variations at the right
places must never have been wanting, or, as I ex-
pressed it before: the useful variations were always
present, But how is that possible in such long exten-
sive lines of dissimilar variations as have gradually
come to constitute markings of the complexity here
presented? Suppose that the useful colors had not

GERMINAL SELECTION. 27

appeared at all, or had not appeared at the right
places? It is a fact that in constant species, that is,
in suck as are not in process of transformation, the
variations of the markings are by no means frequent
or abundant. Or, suppose that they had really ap-
peared, but occurred only in individuals, or in a small
percentage of individuals?

Such are the objections raised against the theory of
selection by its opponents, and put forward as insur-
mountable obstacles to the process. Nor are such ob-
jections relevant only in the case of protective color-
ings; they are applicable in all cases where the process
of selection is concerned. Take the case of instincts
that are called into action only once in life, as, for ex-
ample, the pupal performances of insects, the artificial
fabrication of cocoons, etc. How is it that the useful
variations were always present here? And yet they
must have been present, if such complicated spinning
instincts could have taken their rise as are observable
in the silk-worm, or in the emperor-moth. And they
have been developed, and that in whole families, in
forms varying in all species, and in every case adapted
to the special wants of the species.

Particularly striking is the proof afforded of this
constant presence of the useful variations by cases
where we meet with the development of highly special
adaptations that are uncommon even for the group of
organisms concerned. Such a case, for example, is
the apparatus designed for the capture of small ani-
mals and their digestion, found in widely different
plants and widely separated families. On the other
hand, very common adaptations, such as the eyes of
animals, show distinctly that in all cases where it was
necessary, the useful variations for the formation of

28 GERMINAL SELECTION.

an eye were presented, and were presented further ex-
actly at spots at which organs of vision could perform
their best work: thus, in Turbellaria and many other
worms that live in the light, at the anterior extremity
of the body and on the dorsal surface; in certain
mussels, on the edge of the mantle; in terrestrial snails,
on the antenne; in certain tropical marine snails in-
habiting shallow waters, on the back; and in the
chitons even on the dorsal surface of the shell!

But even taking the very simplest cases of selection,
it is impossible to do without this assumption, that
the useful variations are always present, or that they
always exist in a sufficiently large number of individ-
uals for the selective process. You know the thick-
ness and power of resistance of the egg-shells of
round-worms. The eggs of the round-worms of
horses have been known to continue their course of
development undisturbed even after they had been
thrown into strong alcohol and all other kinds of in-
jurious liquids—much to the vexation of the embry-
ologists, who wished to preserve a definite stage of de-
velopment and sought to kill the embryo at that stage.
Indeed, think of the result, if in the course of their
phylogenesis stout and resistant variations of egg-
shells had not been presented in these worms, or had
not always been presented, or had not been presented
in every generation and not in sufficient quantities.

The cogency of the facts is absolutely overpowering
when we consider that practically no modification
occurs alone, that every primary modification brings
in its train secondary ones, and that these induce
forced modifications in many parts of the body, fre-
quently of the most diversified, or even self-contra-
dictory, forms. Recently Herbert Spencer has drawn

GERMINAL SELECTION. 29

fresh attention to these secondary modifications, which
must always occur in harmony with the primary one,
and has, as he thinks, advanced in this set of facts, a
convincing disproof of the contention that such coa-
daptive modifications of numerous cofunctioning parts
can rest on natural selection. Now, although I deem
his conclusion precipitate, yet the very fact of a sim-
ultaneous, functionally concordant, yet essentially di-
versified modification of numerous parts, points con-
clusively to the circumstance that something is still
wanting to the selection of Darwin and Wallace, which
it is obligatory on us to discover, if we possibly can,
and without which selection as yet offers no complete
explanation of the phyletic processes of transformation.
There is a hidden secret to be unriddled here before we
can obtain a satisfactory insight into the phenomena
in question. We must seek to discover why tt hap-
_pens that the useful variations sare always present.
Herbert Spencer appealed to Lamarck’s principle for
the explanation of coadaptation, and it is certain that
functional adaptation is operative during the individ-
ual life, and that it compensates in a certain measure
the inequalities of the inherited constitutions. I shall
not repeat what I have said before on this subject, nor
maintain, in refutation of Spencer’s contention, that
functional adaptation is itself nothing more than the
efflux of intra-biontic selective processes, as Spencer
himself once suggested in a prophetic moment, but
which it was left for Wilhelm Roux to introduce into
science as “the struggle of the parts” of organisms.*
I shall only remark that if functional adaptations were
themselves inheritable, this would still be insufficient

_1Compare my essay, Neue Gedanken zur Vererbungsfrage,
Jena, 1895, p. 10, second footnote. .

30 GERMINAL SELECTION.

for the explanation of coadaptation, for the reason that
precisely similar coadaptive modifications occur in
purely passively functioning parts, in which, conse-
quently, modification by function is excluded. This
is the case with the skeletal parts of Articulata; e. g.,
it is true of their articular surfaces with their complex ~
adaptations to the most varied forms of locomotion. In
all these cases the ready-made, hard, unalterable, chi-
tinous part is first set into activity; consequently its
adaptation to the function must have been previously
effected, independently of that function. These joints,
and divers other parts, accordingly, have been devel-
oped in the precisest manner for the function, and the
latter could have had no direct share in their forma-
tion. When we consider, now, that it is impossible
that every one of the numerous surfaces, ridges, fur-
rows, and corners found in a single such articulation,
let alone in all the articulations of the body, should
hold in its hands the power of life and death over in-
dividuals for untold successions of generations, the
fact is again unmistakably impressed upon our atten-
tion that the conception of the selective processes which
has hitherto obtained is insufficient, that the root of the
process in fact lies deeper, that it is to be found in
the place where it is determined what variations of the
parts of the organism shall appear—namely in the
germ.

The phenomena observed in the stunting, or degen-
eration, of parts rendered useless, point to the same
conclusion. They show distinctly that ordinary selec-
tion which operates by the removal of entire persons,
personal selection, as I prefer to call it, cannot be the
only cause of degeneration; for in most cases of de-
generation it cannot be assumed that slight individual

GERMINAL SELECTION. 31

vacillations in the size of the organ in question have
possessed selective value. On the contrary, we see
such retrogressions affected apparently in the shape of
a continuous evolutionary process determined by in-
ternal causes, in the case of which there can be no
question whatever of selection of persons or of a sur-
vival of the fittest, that is, of individuals with the
smallest rudiments.

It is this consideration principally that has won so
many adherents for the Lamarckian principle in re-
cent times, particularly among the paleontologists.
They see the outer toes of hoofed animals constantly
and steadily degenerating through long successions of
generations and species, concurrently with the re-en-
forcement of one or two middle toes, which are pre-
ferred or are afterwards used exclusively for step-
ping, and they believe correctly enough that these
results should not be ascribed to the effects of per-
sonal selection alone. They demand a principle which
shall effect the degeneration by internal forces, and be-
lieve that they have found it in functional adaptation.*

1Qn the same day on which the present address was de-
livered at the International Congress of Zodlogists in Leyden,
and on the same occasion, Dr. W. B. Scott, Professor of
Geology in Princeton College, New Jersey, read a very inter-
esting paper on the tertiary mammalian fauna of North Amer-
ica, in which, without a knowledge of my paper, he took his
stand precisely on this argument and arrived at the opinion
that it could not possibly be the ordinary individual varia-
tions which accomplished phyletic evolution, but that it was
necessary to assume in addition phyletic variations. I believe
our views are not as widely remote as might be supposed.
Of course, I see no reason for assuming two kinds of hered-
itary variations, different in origin. Still it is likely that only
a relatively small portion of the numberless individual varia-
tions lie on the path of phyletic advancement and so under

32 GERMINAL SELECTION.

On this last point, now, I believe, they are mistaken,
be they ever so strongly convinced of the correctness
of their view and ever so aggressive and embittered in
their defence of it.

Recently, an inquirer of great caution and calmness
of judgment, Prof. C. Lloyd Morgan, has expressed
the opinion that the Lamarckian principle must at
least be admitted as a working hypothesis. But with
this I cannot agree, at least as things stand at present.
A working hypothesis may be false, and yet lead to
further progress ; that is, it may constitute an advance .
to the extent of being useful in formulating the prob-
lem and in illuminating paths that are likely to lead
to results. But it seems to me that a hypothesis of this
kind has performed its services and must be discarded
the moment it is found to be at hopeless variance with
the facts. If it can be proved that precisely the same
degenerative processes also take place in such super-
fluotts parts as have only passive and not active func-
tions, as is the case with the chitinous parts of the
skeleton of Arthropoda, then it is a demonstrated fact,
that the cessation of functional action is not the ef-
ficient cause of the process of degeneration. At once
your legitimate working hypothesis is transformed
into an illegitimate dogma—illegitimate because it no
longer serves as a guide on the path to knowledge but

the guidance of germinal selection mark out the way of
further development; and hence it would be quite possible
in this sense to distinguish continuous, definitely directed
individual variations from such as fluctuate hither and thither
with no uniformity in the course of generations. The root
of the two is of ‘course the same, and they admit of being
distinguished from each other only by their success, phyletic
modification, or by their failure. ‘

GERMINAL SELECTION. 33

blocks-that path. For the person who is convinced he
has found the right explanation is not going to seek
for it.

I can understand perfectly well the hesitation that
has prevailed on this point in many minds, from their
having seen one aspect of the facts more distinctly than
the other. From this sceptical point of view Osborn
has drawn the following perfectly correct conclusion: ,
“Tf acquired variations are transmitted, there must be)
some unknown principle in heredity; if they are not.
transmitted, there must be some unknown factor in,
evolution.”2 :

Such in fact, is the case and I shall attempt to point
out to you what this factor is. My inference is a very
simple one: if we are forced by the facts on all hands
to the assumption that the useful variations which
render selection possible are always present, then some
profound connection must exist between the utility of
a variation and its actual appearance, or, in other
words, the direction of the variation of a part must be
determined by utility, and we shall have to see whether
facts exist that confirm our conjecture.

The facts do indeed exist and lie before our very
eyes, despite their not having been recognised as such
before. All artificial selection practised by man rests
on the fact that by means of the selection of individuals
having a given character slightly more pronounced
than usual, there is gradually produced a general aug-
mentation of this character, which subsequently
reaches a point never before attained by any individual

1H. F. Osborn, “The Hereditary Mechanism and the Search
for the Unknown Factors of Evolution,” in Biological Lec-
tures delivered at the Marine Biolog. Lab. at Wood’s Holl
in the Summer Session of 1894. Boston, 1895.

34 GERMINAL SELECTION.

of this species. I shall choose an example which seems
to me especially clear and simple because only one
character has been substantially modified here. The
long-tailed variety of domestic cock, now bred in Japan
and Corea, owes its existence to skilful selection and
not at all to the circumstance that at some period
of the race’s history a cock with tail-feathers six feet
in length suddenly and spasmodically appeared. At
the present day even, as Professor Ishikawa of Tokio
writes me, the breeders still make extraordinary efforts
to increase the length of the tail, and every inch gained
adds considerably to the value of the bird. Now
nothing has been done here whatever except always
to select for purposes of breeding the cocks with the
longest feathers; and in this way alone were these
feathers, after the lapse of many generations, pro-
longed to a length far exceeding every previous varia-
tion. ‘

I once asked a famous dove-fancier, Mr. W. B.°
Tegetmeier of London, whether it was his opinion that,
by artificial selection alone a character could be aug-
mented. He thought a long time and finally said: “It
is without our power to do anything if the variation
which we seek is not presented, but once that variation
‘is given, then I think the augmentation can be ef-
fected.” And that in fact is the case. If cocks had
never existed whose tail-feathers were a little longer
than usual the Japanese breed could never have orig-
inated; but as the facts are, always the cocks with the
longest feathers were chosen from each generation,
and these only were bred, and thus a hereditary aug-
mentation of the character in question was effected,
which would hardly have been deemed, possible.

Now what does this mean? Simply that the hered-

GERMINAL SELECTION. 35

itary diathesis, the constitutional predisposition
(Anlage) of the ‘breed was changed in the respect in
question, and our conclusion from this and numerous
similar facts of artificial selection runs as follows: by
the selection alone of the plus or minus variations of a
character,is the constant modification of that character
in the plus or minus direction determined. Obviously
the hereditary diminution of a part is also effected
by the simple selection of the individuals in each gen-
eration possessing the smallest parts, as is proved, for
example, by the tiny bills and feet of numerous breeds
of doves. We may assert, therefore, in general terms:
a definitely directed progressive variation of a given
part is produced by continued selection in that definite
direction. This is no hypothesis, but a direct inference
from the facts and may also be expressed as follows:
By a selection of the kind referred to,the germ is pro-
gressively modified in a manner corresponding with
the production of a definitely directed progressive
variation of the part. ;

In this general form the proposition is not likely to
encounter opposition, as certainly no one is prepared
to uphold the view that the germ remains unchanged
whilst the products proceeding from it, its descend-
ants, are modified. On the contrary, all will agree
when I say that the germ in this case must have under-
gone modifications, and that their character must cor-
respond with the modifications undergone by its prod-
ucts. Thus far, then, we find ourselves, not on the
ground of the hypothesis that has been lately so much
maligned, but on the ground of facts and of direct
inferences from facts. But if we attempt to pierce
deeper into the problem, we are in need of the hy-
pothesis.

36 GERMINAL SELECTION.

The first and most natural explanation will be this
—that through selection the zero-point, about which,
figuratively speaking, the organ may be said to oscil-
late in its plus and minus variations, is displaced up-
wards or downwards. Darwin himself assumed that
the variations oscillated about a mean point, and the
statistical researches of Galton, Weldon, and others
have furnished a proof of the assumption. If selec-
tion, now, always picks out the plus variations for
imitation, perforce, then, the mean or zero-point will be
displaced in the upward direction, and the variations
of the following generation will oscillate about a
higher mean than before. This elevation of the zero-~
point of a variation would be continued in this manner
until the total equilibrium of the organism was ‘in
danger of being disturbed.

There is involved here, however, an assumption
which is by no means self-evident, that every advance-
ment gained by the variation in question constitutes
a new centre for the variations occurring in the fol-
lowing generation. That this is a fact, is proved by
such actual results of selection as are obtained in the
case of the Japanese cock. But the question remains,
Why is this the fact?

Now here, I think, my theory of determinants gives
a satisfactory answer. According to that theory every
independently and hereditarily variable part: is tepre-
sented in the germ by a determinant, that is by a de-
terminative group of vital units, whose size and power
of assimilation correspond to the size and vigor of the
part. These determinants multiply, as do all vital
units, by growth and division, and necessarily they in-
crease rapidly in every individual, and the more
rapidly the greater the quantity of the germinal cells

GERMINAL SELECTION. 37

the individual produces. And since there is no more
reason for excluding irregularities of passive nutrition,
and of the supply of nutriment in these minute, micro-
scopically invisible parts, than there is in the larger
visible parts of the cells, tissues, and organs, conse-
quently the descendants of a determinant can never all
be exactly alike in size and capacity of assimilation, but
they will oscillate in this respect to and fro about the
maternal determinant as about their zero-point, and will
be partly greater, partly smaller, and partly of the same
size as that. In these oscillations, now, the material
for further selection is presented, and in the inevitable
fluctuations of the nutrient supply I see the reason
why every stage attained becomes immediately the
zero-point of new fluctuations, and consequently why
the size of a part can be augmented or diminished by
selection without limit, solely by the displacement of
the zero-point of variation as the result of selection.
We should err, however, if we believed that we had
penetrated to the root of the phenomenon by this in-
sight. There is certainly some other and mightier
factor involved here than the simple selection of per-
sons and the consequent displacement of the zero-
point of variation. It would seem, indeed, as if in
one case, videlicet, in that of the Japanese cock, the
augmentation of the character in question were com-
pletely explained by this factor alone. In fact, in this
and similar cases we cannot penetrate deeper into the
processes of variation, and therefore cannot say a
priori whether other factors have or have not been in-
volved in the augmentation of the character in ques-
tion—other characters, that is, than the simple dis-
placement of the zero-point. There is, however, an-
other class of phyletic modifications, which point

38 GERMINAL SELECTION.

unmistakably to the conclusion that the displacement
of the zero-point of variation by personal selection is
not and cannot be the only factor in the determination
and accomplishment of the direction of variation. I
refer to retrogresswe development, the gradual degen-
eration of parts or characters that have grown useless,’
the gradual disappearance of the eye in cave-animals,
of the legs in snakes and whales, of the wings in cer-
tain female butterflies, in short, to that entire enor-
mous mass of facts comprehended under the designa-
tion of “rudimentary organs.”

I have endeavored on a previous occasion to point
out the significance of the part played in the great
process of animate evolution by these retrogressive
growths, and I made at the time the statement that
“the phenomena of retrogressive growth enabled us in
a greater measure almost than those of progressive
growth to penetrate to the causes which produce the
transformations of animate nature.” Although at that
time! I had no inkling of certain processes which to-
day I shall seek to prove the existence of, yet my
statement receives a fresh confirmation from these
facts.

For, in most retrogressive processes active selection
in Darwin's sense plays no part, and advocates of the
Lamarckian principle, as above remarked, have rightly
denied that active selection, that is, the selection of
individuals possessing the useless organ in its most
reduced state, is sufficient to explain the process of
degeneration. I, for my part, have never assumed this,

1In 1886. See my paper on “Retrogression in Nature,”
published in English in Nos. 105, 107, 108, and 109 of The
Open Court, and also in my essays on Heredity, Jena, 1892.

GERMINAL SELECTION. 39

and I enunciated precisely on this account the princi-
ple of panmixia. Now, although this, as I still have
no reason for doubting, is a perfectly correct principle,
which really does have an essential and indispensable
share in the process of retrogression, still it is not
alone sufficient for a full explanation of the phe-
nomena. My opponents, in advancing this objection,
were right, to the extent indicated and as I expressly
acknowledge, although they were unable to substitute
anything positive in its stead or to render my explana-
tion complete. The very fact of the cessation of con-
trol over the organ is sufficient to explain its degenera-
tion, that is, its deterioration, the disharmony of its
parts, but not the fact which actually and always
occurs where an organ has become useless—viz., tts
gradual and unceasing diminution continuing for
thousands and thousands of years culminating in its
final and absolute effacement.

If, now, neither the selection of persons nor the ces-
sation of personal selection can explain this phenom-
enon, assuredly some other principle must be the effi-
cient cause here, and this cause I believe I have indi-
cated in an essay written at the close of last year and
only recently published.t I call it germinal selection.

The principle in question reposes on the application,
made some fifteen years ago by Wilhelm Roux, of the
principle of selection to the parts of organisms—on the
struggle of the parts, as he called it. If such a strug-
gle obtains among organs, tissues, and cells, it must
also obtain between the smallest and for us invisible
vital particles, not only between those of the body-
cells, strictly so called, but also between those of the

1 Neue Gedanken sur Vererbungsfrage, Jena, 1895.

40 GERMINAL SELECTION.

germinal cells. Roux himself spoke of the struggle —

of the molecules, by which he presumably understood |

the smallest ultimate units of vital phenomena—ele- ©

ments which De Vries designated pangenes, Wiesner
plasomes, and I biophores, after Briicke’s: ingenious
conception! of these invisible entities had been almost

totally forgotten, or at least had lain unnoticed for |

thirty years. No struggle, as that is understood in
the theory of selection, could take place between real

. 1Del4ge, in La structure du protoplasma et les théories sur

Phérédité, etc., Paris, 1895, is mistaken in attributing to Her- —

bert Spencer the merit of having first pointed out the neces-
sity of the assumption of biological units ranking between the
molecule and the cell. Briicke set forth this idea three
years previously to Spencer and established it exhaustively
in a paper which in Germany at least is famous (“Elemen-
tarorganismen,” Wiener Sitzungsberichte, October 10, 1861,
Vol. XLIV., IL. p. 381). Spencer’s Principles of Biology ap-
peared between 1864 and 1868; consequently there can be
no dispute touching the priority of the idea. Strangely
enough Delage cites Briicke’s. essay in the Bibliographical
Index at the end of his book correctly, although Briicke’s
name and views are nowhere mentioned in the book itself.

It is to be observed, however, that the elementary organisms. *

of Briicke are not merely the precursors of Spencer’s “phys-
iological units,” but repose on much firmer foundations than
the latter, which, as Delage himself remarks, are at bottom
nothing more than magnified molecules and not combinations
of different molecules of such character as to produce neces-
sarily phenomena of life. He aptly remarks on this point:
“the physiological units of Spencer are only chemical mole-
cules of greater complexity than the rest, and as he defines
them they would be regarded as such by every chemist. He
attributes to them no property essentially different from
those of chemical molecules.” Assimilation, growth, propa-
gation, in short the attributes of life, are not attributed by
Spencer to his units, while Briicke by his very designation
“elementary organisms” expresses the idea of “ultimate living

GERMINAL SELECTION. 41

molecules, for molecules are neither nourished, sub-
ject to growth, nor propagated.

The gradual degeneration of organs grown useless
may be explained, now, by the theory of determinants
very simply and without any co-operation on the part
of active personal selection, as follows.

Nutrition, it is known, is not merely a pas-
sive process. A part is not only nourished but
also actively nourishes itself, and the more vigor-
ously, the more powerful and capable of assimila-
tion it is. Hence powerful determinants in the germ
will absorb nutriment more rapidly than weaker deter-
minants. The latter, accordingly, will grow more
slowly and will produce weaker descendants than the
former.

Let us assume, now, that a part of the body, say
the hinder extremities of the quadruped ancestors of

units,” to use Wiesner’s phrase. Of course this particular
aspect of the vital units was not emphasised by Briicke with
the same distinctness and sharpness as by recent inquirers,
who took up Briicke’s ideas thirty years after. I refer to
the conception that the union of a definite combination of
heterogeneous molecules into an invisibly small unit, forms
the cradle or focus of the vital phenomena. This was first
done and apparently on independent considerations by De

é

Vries, and soon after by Wiesner, and subsequently by myself ,

(De Vries, Intracellulire Pangenesis, Jena, 1889; Wiesner,
Die Elementarstructur und das Wachsthum der lebenden
Substanz, Vienna, 1892; Weismann, Das Keimplasma, Jena,
1892). Let me say at the close of this note that it is not my
intention in thus defending the rights of a great physiologist,
to censure in the least the distinguished author of L’hérédité
who has set himself a remarkably high standard of exactitude
in such matters. Certainly, when we consider the enormous
extent of the literature that had to be mastered to produce
his book, embracing as it did all the various theories of recent
times, stich an oversight is quite excusable.

42 GERMINAL SELECTION.

our common whales, are rendered useless. Panmixia
steps in, 7. e., selection ceases to influence these organs.
Individuals with large and individuals with small hind
legs are equally favored in the struggle for existence.

From this fact alone would result a degradation of
the organ, but of course it would not be very marked
in extent, seeing that the minus variations which occur
are no longer removed. According to our assumption,
however, such minus variations repose on the weaker
determinants of the germ, that is, on such as absorb
nutriment less powerfully than the rest. And since
every determinant battles stoutly with its neighbors
for food, that is, takes to itself as much of it as it
can, consonantly with its power of assimilation and
proportionately to the nutrient supply, therefore the
unimpoverished neighbors of this minus determinant
will deprive it of its nutriment more rapidly than was
the case with its more robust ancestors; hence, it will
be unable to obtain the full quantum of food corre-
sponding even to its weakened capacity of assimilation,
and the result will be that its ancestors will be weak-
ened still more. Inasmuch, now, as no weeding out of
the weaker determinants of the hind leg by personal
selection takes place on our hypothesis, inevitably the
average strength of this determinant must slowly but
constantly diminish, that is, the leg must grow smaller
and smaller until finally it disappears altogether. The
determinants* of the useless organ are constantly at

1I speak here of determinants, not of groups of determi-
nants, which is the more correct expression, merely for the
sake of brevity. It is a matter of course that a whole
extremity, such as we have here chosen, cannot be repre-
sented in the germ by a single determinant only, but requires
a large group of determinants.

GERMINAL SELECTION. 43

a disadvantage as compared with the determinants
of their environment in the germinal tenement, because
no assistance is offered to them by personal selection
after they have once been weakened by a decrease of
the passive nutrient influx. Nor is the degeneration
stopped by the uninterrupted crossing of individuals
in sexual propagation, but only slightly retarded. The
number of individuals with weaker determinants must,
despite this fact, go on increasing from generation to
generation, so that soon every determinant that still
happens to be endowed with exceptional vigor will be
confronted by a decided overplus of weaker determi-
nants, and by continued crossing therefore will become
‘more and more impoverished. Panmixia is the indis-
pensable precondition of the whole process; for owing
to the fact that persons with weak determinants are
just as capable of life as those with strong, owing to
the fact that they cannot now, as formerly, when the
organ was still useful, be removed by personal selec-

_ tion, solely by this means is a further weakening ef-
fected in the following generations—in short, only
by this means are the determinants of the useless organ
brought upon the inclined plane, down which they
are destined slowly but incessantly to slide towards
their completed extinction.

The foregoing explanation will be probably accepted
as satisfactory in a purely formal regard, but it will be
objected that, even granting this, it has not yet been
proved to be the correct one. In answer I can of
course adduce nothing except that it is at present the
only one that can be given. It may be that the actual
state of things in nature is different, but if it can be
shown that a self-direction of variation merely from
the need of it is at all conceivable by mechanical means,

44 GERMINAL SELECTION.

that in itself, it seems to me, is a decided gain. It

must also not be forgotten that some process or other ©

must take place in the germ-plasm when an organ
becomes rudimentary, and that as the result of it this
organ, and only this organ, must disappear. Now in
what shall this process consist, if not in a modification
of the constitution of the germ? And how could the
effect of such a modification be limited only to one
organ which was becoming rudimentary if the modi-
fication itself were not a local one? These are ques-

Hand

tions which it is incumbent on those to answer who

conceive the germinal substance to be composed of like
units.

Applying, now, the explanation derived from the dis-
appearance of organs to the opposed transformation,
namely, to the enlargement of a part, the presumption
lies close at hand that the production of the long tail-
feathers of the Japanese cock does not repose solely on
the displacement directly effected by personal selection,
of the zero-point of variation upwards, but that it is
also fostered and strengthened by germinal selection.
Were that not so, the phenomena of the transmuta-
tion of species, in so far as fresh growth and the en-
largement and complication of organs already present
are concerned, would not be a whit more intelligible
than they were before. We should know probably
how it comes to pass that the constitutional predis-
position (group of determinants) of a single organ is
intensified by selection, but the flood of objections
against the theory of selection touching its inability
to modify many parts at once would not be repressed
by such knowledge. The initial impulse conditioning
the independent maintenance of the useful direction
of variation in the germ-plasm must rather be sought

GERMINAL SELECTION. 45

in the utility of the modification itself, and this also
seems to me intelligible from the side of the theory.
For as soon as personal selection favors the more
powerful variations of a determinant, the moment that
these come to predominate in the germ-plasm of the
species, at once the tendency must arise for them to
vary still more strongly in the plus direction, not solely
because the zero-point has been pushed farther up-
wards, but because they themselves now oppose a
relatively more powerful front to their neighbors, that
is, actively absorb more nutriment, and upon the whole
increase in vigor and produce more robust descendants.
From the relative vigor or dynamic status of the parti-
“cles of the germ-plasm, thus, will issue spontaneously
an ascending line of variation, precisely as the facts of
evolution require. For, as I have already said, it is not
sufficient that the augmentation of a character should
be brought about by uninterrupted personal selection,
even supposing that the displacement of the zero-point
were possible without germinal selection.

Thus, I think, may be explained how personal selec-
tion imparts the initial impulse to processes in the
germ-plasm, which, when they are once set agoing,
persist of themselves in the same direction, and are,
therefore, in no need of the continued supplementary
help of personal selection, as directed exclusively to
a definite part. If but from time to time, that is, if
upon the average the poorest individuals, the bearers
of the weakest determinants, are eliminated, the varia-
tional direction of the part in question, now reposing
on germinal selection, must persist, and it will very
slowly but very surely increase until further develop-
ment is impeded by its inutility and personal selection

46 GERMINAL SELECTION.

arrests the process, that is, ceases to eliminate the
weaker individuals.

In this manner it becomes intelligible how a large
number of modifications varying in kind and far more
so in degree can be guided simultaneously by persona’
selection; how in strict conformity with its adaptive
wants every part is modified, or preserved unmodified
how a given articulation can undergo modifications,
causing it to disappear on one side, to grow in volume
on another, and to continue unaltered on a third. For
every part that is perfectly adapted, although it can
fluctuate slightly, yet can never undergo a permanent
alteration in the ascending or descending direction
because every plus and every minus variation which
has attained selective value would be eliminated by
personal selection’ in the course of time. Therefore,
a definite direction of variation cannot arise in such
cases and we have also reached, as it seems to me,
a satisfactory explanation of the constancy of well-
adapted species and characters.

Hitherto I have spoken only of plus and minus varia-
tion. But there exist, as we know, not only variations
of size but also variations of kind; and the coloration
of the wings of butterflies, which we chose above as
our example, would fall, according to the ordinary
usage of speech, under just this head of variations
of quality. The question arises, therefore, Have the
principles just developed any claim to validity in the
explanation of qualitative modifications ?

In considering this question it should be carefully

GERMINAL SELECTION. 47

tions, cannot be reduced to the processes of augmenta-
tion described, inasmuch as these, by their very na-
ture, can be effected only in living elements
capable of increase by propagation; but the interfer-
ence of selection does not begin originally with the
constitutional predisposition (Anlagen) of the germ,
i. e. with the determinants, but with the ultimate units
of life, the biophores.

A determinant must be composed of heterogeneous
biophores, and on their numerical proportion reposes,
according to our hypothesis, their specific nature. If
that proportion is altered, so also is the character of
the determinant. But disturbances of this numerical
proportion must result at once on proof of their use-
fulness, or as soon as the modifications deter-
mined thereby in the inward character of the deter-
minant turn out to be of utility. For fluctuations of
nutriment and the struggle for nutriment, with its\
sequent preference of the strongest, must take place
between the various species of the biophores as well as:
between the species of the determinants. But changes
in the quantitative ratios of the biophores appear to
us qualitative changes in the corresponding deter-

“determinant, for example, that of a hair, may on its
development appear to us as a qualitative change, a
spot on the skin where previously only isolated hairs
stood being now densely crowded with them, and as-
suming thus the character of a downy piece of fur.
The single hair need not have changed in this process,
and yet the spot has virtually undergone a qualitative
modification: The majority of the changes that appear (
to us qualitative rest on invisible quantitative changes,
and such can be produced at all times and at all stages /

48 GERMINAL SELECTION.

of the vital units by germinal selection. In a simila
manner are induced the most varied qualitativ
changes of the corresponding determinants and of th
characters conditioned thereby, just as changes in thi
numerical proportions of atoms produce essentia
changes in the properties of a chemical molecule.
In this way we acquire an approximate conceptior
of the possible mechanical modus operandi of actua
events—namely, of the manner in which the usefu
variations required by the conditions of life can al.
ways, that is, very frequently, make their appearance
This possibility is the sole condition of our being abl
to understand how different parts of the body, abso
lutely undefined in extent, can appear as variationa
units and vary in the same or in different directions
according to the special needs of the case, or as thi
conditions of life prescribe. Thus, for example, in th
case of the butterfly’s wings it rests entirely witl
utility to decide the size.and the shape of the spot
that shall vary simultaneously in the same direction
At one time the whole under surface of the wing ap
pears as the variational unit and has the same color
at another the inside half, which is dark, is contraste:
with the outside half which is bright; or the same con
trast will exist between the anterior and posterio
halves; or, finally, narrow stripes or line-shape
streaks will behave as variational units and form con
trasts with manifold kinds of spots or with the broade
intervals between them, with the result that the pictur
of a leaf or of another protected species is produced.
I must refrain from entering into the details of suc
cases and shall illustrate my views regarding the colo1
transformations of butterflies’ wings by the simple:

GERMINAL SELECTION. 49

conceivable example—viz. that of the uniform change
of color on the entire under surface of the wing.
Suppose, for example, that the ancestral species of
a certain forest-butterfly habitually reposed on
branches which hung near the ground and were cov-
ered with dry or rotten leaves; such a species would
assume on its under surface a protective coloring
which by its dark, brown, yellow, or red tints would
tend toward similarity with such leaves. If, however,
the descendants of this species should be subsequently
compelled, no matter from what cause, to adopt the
habit of resting on the green-leafed branches higher
up, then from that period on the brown coloring would
act less protectively than the shades verging towards
green. And a process of selection will have set in
which consisted first in giving preference only to such
persons whose brown and yellow tints showed a ten-
dency to green. Only on the assumption that such
shades were possible by a displacement in the quanti-
tative proportions of the different kinds of biophores
composing the determinants of the scales affected, was
a further development in the direction of green possi-
ble. Such being the case, however, that development
had to result; because fluctuations in the numerical
proportions of the biophores are always taking place,
and consequently the material for germinal selection
is always at hand. At present it is impossible to deter-
mine exactly the magnitude of the initial stages of the
deviations thus brought about and promoted by the
sexual blending of characters; but it may perhaps be
ascertained in the future, with exceptionally favorable
material. Pending such special observations, however,
it can only be said a priori that slight changes in the
composition of a determinant do not necessarily condi-

50 GERMINAL SELECTION.

tion similar slight deviations of the corresponding
character,—in this case the color,—just as slight
changes in the atomic composition of a molecule may
result in bestowing upon the latter widely different
properties. As soon, however, as the beginning has
been made and a definite direction has been imparted
to the variation, as the result of this or that primary
variation’s being’ preferred, the selective process must
continue until the highest degree of faithfulness re-
quired by the species in the imitation of areeh leaves
has been attained.

That the foregoing process has actually taken place
is evidenced not only by the presence of the beginnings
of such transformations, as found for example in some
greenish-tinted specimens of Kallima, but mainly by
certain species of the South American genus Cato-
nephele, all of which are forest-butterflies, and which,
with many species having dark-brown under surfaces,
present some also with bright green under surfaces—
a green that is not like the fresh green of our beech
and oak trees, but resembles the bright under surface
of the cherry-laurel leaf, and is the color of the under
surfaces of the thick, leathery leaves, colored dark-
green above, borne by many trees in the tropics.

The difference between this and the old conception
of the selection-process consists not only in the fact
that a large number of individuals with the initial
stages of the desired variation is present from the

_ beginning, for always innumerable plus and minus
variations exist, but principally in the circumstance
that the constant uninterrupted progress of the proc-
ess after it is once begun is assured, that there can
never be a lack of progressively advantageous varia-
tions in a large number of individuals. Selection,

GERMINAL SELECTION. 51

therefore, is now not compelled to wait for accidental
variations but produces such itself, whenever the re-
quired elements for the purpose are present. Now,
where it is a question simply of the enlargement or
diminution of a part, or of a part of a part, these varia-
tions are always present, and in modifications of qual-
ity they are at least present in many cases.

This is the only way in which I can see a possibility
of explaining phenomena of mimicry—the imitation
of one species by another. The useful variations must
be produced in the germ itself by internal selection-
processes if this class of facts is to be rendered intel-
ligible. I refer to the mimicry of an exempt species
by two or three other species, or, the aping of different
exempt patterns by one species in need of protection.
It must be conceded to Darwin and Wallace that some
degree of similarity between the copy and the imita-
tion was present from the start, at least in very many
cases ;! but in no case would this have been sufficient
had not slight shades of coloring afforded some hold
for personal selection, and in this way furnished a
basis for independent germinal selection acting only
in the direction indicated. It would have been im-
possible for such a minute similarity in the design,
and particularly in the shades of the coloration, ever to
have arisen, if the process of adaptation rested entirely

1 That this is not so in all cases has recently been shown
by Dixey from observations on certain white butterflies of
South America which mimic the Heliconids and in which a
small, yellowish red streak on the under surface of the hind
wing has served as the point of departure and groundwork
of the development of a protective resemblance to quite
differently colored Heliconids. “On the Relation of Mimetic
Characters to the Original Form,” in “the Report of the British

Association for 1894.

52 GERMINAL SELECTION.

on personal selection. Were this so, a complete scale
of the most varied shades of color must have been
continually presented as variations in every species,
which certainly is not the case. For example, when
the exempt species Acrea Egina, whose coloration is
a brick-red, a color common only in the genus Acrea,
is mimicked by two other butterflies, a Papilio and a
Pseudacrea, so deceptively that not only the cut of
the wings and the pattern of their markings, but also
that precise shade of brick-red, which is scarcely ever
met with in diurnal butterflies, are produced, assuredly
stich a result cannot rest on accidental, but must be
the outcome of a definitely directed, variation, pro-
duced by utility. We cannot assume that such a col-
‘oration has appeared as an accidental variation in just
and in only these two species, which fly together with
the Acrea in the same localities of the same country
and same part of the world—the Gold Coast of Africa.
It is conceivable, indeed, that non-directed variation
should have accidentally produced this brick-red in
a single case, but that it should have done so three
times and'in three species, which live together but
are otherwise not related, is a far more violent and
improbable assumption than that of a causal connexion
of this coincidence. Now hundreds of cases of such
mimicry exist in which the color-tints of the copy are
met with again in more or less precise and sometimes
in exceedingly exact imitations, and there are thou-
sands of cases in which the color-tint of a bark, of
a definite leaf, of a definite blossom, is repeated exactly
in the protectively colored insect. In such cases there
can be no question of accident, but the variations pre-
sented to personal selection must themselves have
been produced by the principle of the survival of the

GERMINAL SELECTION. 53

fii! And this is effected, as I am inclined to believe,
through such profound processes of selection in the
interior of the germ-plasm as I have endeavored to
sketch to you to-day under the title of germinal se-
lection. ,

I am perfectly well aware how schematic my pres-
entation of this process is, and must be at present,
owing mainly to our inability to gain exact knowledge
concerning the fundamental germinal constituents here
assumed. But I regard its existence as assured, al-
though I by no means underrate the fact that emi-
nent thinkers, like Herbert Spencer, contest its validity
and believe they are warranted in assuming a germ
which is composed of similar units. I strongly doubt
whether even so much as a formal explanation of the
phenomena can be arrived at in this manner. So far
as direct observation is concerned, the two theories
stand’ on an equal footing, for neither my dissimilar,
nor Spencer’s similar, units of germinal substance
can be seen directly.

The attempt has been recently made to discredit
my Anlagen, or constitutional germ-elements, on the
ground that they are simply a subtilised reproduc-
tion of Bonnet’s old theory of preformation.*’ This

1 Oscar Hertwig, Zeit- und Streitfragen der Biologie, Jena,
1894. It is customary now to look upon the preformation-
theory of Bonnet as a discarded monstrosity, and on the
epigenesis of K. F. Wolff as the only legitimate view, and to
draw a parallel between these two and what might be called
to-day “evolution” [i. e. unfoldment] and epigenesis. The
evolution, or unfoldment, of Bonnet and Harvey, however,
was something totally different from modern doctrines of
evolution, and Whitman is quite right when he says that
even my theory of determinants would have appeared to the
inquirers of the last century as “extravagant epigenesis.”

54 GERMINAL SELECTION.

impression is very likely based upon ignorance of the
real character of Bonnet’s theory. I will not go into
further details here, particularly as Whitman, in sev-
eral excellently written and finely conceived essays,
has recently afforded opportunity for every one to
inform himself on the subject. My “determinants and
"groups of determinants have nothing to do wit h the
preformations of Bonnet; in a sense they are the.
exact opposites of them; they ‘are simply ‘those “living
parts of the germ whose presence determines the ap-
pearance of a definite organ of a definite character in

Biologists in that day were concerned with quite different
questions from what they are at present, and although now we
probably all share the conviction of Wolff that new characters
do arise in the course of evolution, yet the acceptance of
this view is far from settling the question as to how these
new characters are established in the germ-substance—for in
this substance they certainly must have their foundation.
When, therefore, O. Hertwig laments over my regarding
evolution and not epigenesis as the correct foundation of the
theory of development, his sorrow is almost as naive as is the
statement of Bourne that-epigenesis is a fact and not a theory
(“a statement of morphological fact,” Science Progress, April,
1894, page 108), or, as is the latter’s unconsciousness that
facts originally receive their scientific significance from
thought, i. e. from their interpretation and combination, and
that thought is theory. And when S. Minot, as the leader
of the embryologists, carries his zeal to the pitch of. issuing
a general pronunciamento against me as a corruptor of
youth, in which he declares it-to be a “scientific duty to
protest in the most positive manner against Weismann’s the-
ory,” I wonder greatly that he does not suggest the casting
of a general ballot in the matter. (See the Biologisches
Centralblatt of August 1, 1895.) We see how with these
gentlemen the wisdom of the recitation-room regarding the
infallibility of epigenesis has grown into a dogma, and who-
ever ventures to disturb its foundations must be burnt as a
heretic.

GERMINAL SELECTION. 55

the course of normal evolution. In this form they
appear to me to be an absolutely necessary and un-
avoidable inference from the facts. There must be
contained in the germ,parts that correspond to definite
parts of the complete organism, that is, parts that con-
stitute the reason why such other parts are formed.

It is conceded even by my opponents that the rea-
son why one egg produces a chicken and another a
duck is not to be sought in external conditions, but lies

in a difference of the germinal substance. Nor can.

they deny that a difference of germinal substance
must also constitute the reason why a slight hered-
itary difference should exist between two filial organ-

isms. Should there now, in a possible instance, be

present between them a second, a third, a fourth, or a
hundredth difference of hereditary character, each of
which could vary from the germ, then, certainly, some
second, third, fourth, or hundredth part of the germ
‘must have been different; for whence, otherwise,
should the heredity of the differences be derived, see-
ing that external influences affecting the organism in
the course of evolution induce only non-transmissible
and transient deviations? But the fact that every
complex organism is actually composed of a very large
number of parts independently alterable from the
germ, follows not only from the comparison of allied
species, but also and principally from the experiments
long conducted by man in artificial selection, and
by the consequent and not infrequent change of only
a single part which happens to claim his interest; for
example, the tail-feathers of the cock, the fruit of the
gooseberry, the color of a single feather or group of
feathers, and so on. But a still more cogent proof
is furnished by the degeneration of parts grown use-

59 GERMINAL ‘SELECTION.

less, for this process can be carried on to almost any
extent without the rest of the body necessarily becom-
ing involved in sympathetic alteration. Whole mem-
bers may become rudimentary, like the hind limbs
of the whale, or it may be only single toes or parts of
toes; the whole wing may degenerate in the females
of a butterfly species, or only a small circular group
of wing-scales, in the place of which a so-called “win-
dow” arises. A single vein of the wing also may de-
generate and disappear, or the process may affect only
a part of it, and this may happen in one sex only
of a species. In such cases the rest of the body may
remain absolutely unaltered; only a stone is taken out
of the mosaic.

The assumption, thus, appears to me irresistible,
that every such hereditary and likewise independent
and very slight change of the body rests on some
alteration of a single definite particle of the germinal
substance, and not as Spencer and his followers would
have it, on a change of all the units of the germ. If
the germinal substance consisted wholly of like units, .
then in every change, were it only of a single char-
acter, each of these units would have to undergo ex-
actly the same modification. Now I do not see how
this is possible.

But it may bé that Spencer’s assumption is the
simpler one? Quite the contrary, its simplicity is
merely apparent. Whilst my theory needs for each
modification only a modification of one constitutional
element of the germ, that is, of one particle of the
germinal substance, according to Spencer every par-
ticle of that substance must change, for they are all
supposed to be and to remain alike. But seeing that
all hereditary differences, be they of individuals, races,

GERMINAL SELECTION. 57

or species, must’ be contained in the germ, the obli-
gation rests on these similar units, or rather the ca-
pacity is required of them, to produce in themselves
a truly enormous number of differences. But this is
possible only provided their composition is an exceed-
ingly complex one, or only on the condition that in
every one of them are contained as many alterable par-
ticles as according to my view there are contained
determinants in the whole germ. The differences that
I put into the whole germ, Spencer and his followers
are obliged to put into every single unit of the germ-
inal substance. My position on this point appears to
me incontrovertible so long as it is certain that the
single characters can vary hereditarily; for, if a thing
can vary independently, that is, of its own accord, and
from the germ, then that thing must be represented in
the germ by some particle of the substance, and be
represented there in such wise that a change of the
representative particle produces no other change in
the organism developing from the germ than such as
are connected with the part which depends on it. 1
conceive that even on the assumption of my constitu-
tional elements (Anlagen) the germ-plasm is complex
enough, and that there is no need of increasing its
complexity to a fabulous extent. Be that as it may,
the person who fancies he can produce a complex
organism from a really simple germinal substance is
mistaken: he has not yet thoroughly pondered the
problem. The so-called “epigenetic” theory with its
similar germinal units is therefore naught else than
an evolution-theory where the primary constitutional
elements are reduced to the molecules and atoms—
a view which in my judgment is inadmissible. A real

58 GERMINAL SELECTION.

epigenesis from absolutely homogeneous and not
merely like units is not thinkable. ;
All value has been denied my doctrine of determin-
ants! on the ground that it only shifts the riddles of
evolution to an invisible terrain where it is impossible
for research to gain a foothold.
Now I have indeed to admit that no information

- can be gained concerning my determinants, either with
| the aided or with the unaided eye. But fortunately
there exists in man another organ which may be of

use in fathoming the riddles of nature and this organ

. which is called the brain has in times past often borne

him out in the assumption of invisible entities—entities

' that have not always proved unfruitful for science by
reason of that defect, in proof whereof we may in-

stance the familiar assumptions of atoms and mole-
cules. Probably the biophores also will be included

under that head if the determinants should be ad-
judged utterly unproductive. But so far I have always
held that assumptions of this kind are really produc-

itive, if they are only capable of being used, so to

speak, as a formula, whereby to perform our compu-
tations, unconcerned for the time being as to’ what

shall be its subsequent fate. Now, as I take it, the

determinants have had fruitful results, as their appli-
cation to various biological problems shows. Is it no
advance that we are able to reduce the scission of a
form of life into two or several forms subject to sep-
arately continued but recurrent changes,—I refer to
dimorphism and polymorphism,—that we are able to
reduce such phenomena to the formula of male, female,
and worker determinants? It has been, I think, ren-

1Oscar Hertwig, Zeit- und Streitfragen der Biologie, Jena,
1894.

GERMINAL SELECTION. 59

dered conceivable how these diverse and extremely
minute adaptations could have developed side by side
in the same germ-plasm, under the guidance of selec-
tion; how sterile forms could be hereditarily estab-
lished and transformed in just that manner which
best suits with their special duties; and how they
themselves under the right circumstances could sub-
sequently split up into two or even into three new
forms. Surely at least the unclear conception of an
adaptively transformative influence of food must be
discarded. It is true, we cannot penetrate by this
hypothesis to the last root of the phenomena. The
hotspurs_ of biology, who clamor to know forthwith
how the molecules behave, will scarcely repress their
dissatisfaction’ with such provisional knowledge—for-
getful that all our knowledge is and remains through-
out provisional.

But I shall not enter more minutely into the ques-
tion whether epigenesis or evolution is the right foun-
dation of the theory of development, but shall content
myself with having shown, first, that it is illusory to
imagine that epigenesis admits of a simpler structure
of the germ, (the precise opposite is true,) and sec-
ondly, that there are phenomena that can be understood
only by an evolution-theory. Such a phenomenon is

1 Nor will those, who demand a demonstration of “how the
biophores and determinants are constituted in every case,
and must be arranged in the architecture of the germ-plasm.”
(O. Hertwig, loc. cit., p. 137). As if any living being could
have the temerity even so much as to guess at the
actual ultimate phenomena in evolution and heredity ! The
whole question is a matter of symbols only, just as itis in the
matter of “forces,” “atoms,” “ether undulations,” etc., the
only difference being that in biology we stumble much earlier

60 GERMINAL SELECTION.

the guidance of variation by utility, which we ha
considered to-day. For without primary constituer
of the germ, whether they are called as I call thei
determinants, or something else, germinal selectio
or guidance of variation by personal selection, is ir
possible; for where all units are alike there can |
no struggle, no preference of the best. And yet su
a guidance of variation exists and demands its e
planation, and the early assumptions of a “definite
directed variation” such as Nageli and Askenasy ma
are insufficient, for the reason that they posit on
internal forces as the foundations thereof, and t
cause, as I have attempted to show, the harmony of t
direction of variation with the requirements of t
conditions of life subsists and represents the ridc
to be solved. The degree of adaptiveness which
part possesses itself evokes the direction of variati
of that part.

This proposition seems to me to round off the whc
theory of selection and to give to it that degree of i
ner perfection and completeness which is necessary-
protect it against the many doubts which have gat
ered around it on all sides like so many lowerii
thunder-clouds. The moment variation is determin
substantially though not exclusively by the adaptiv
ness itself, all these doubts fall to the ground, wi
one exception, that of the utility of the initial stey
But just this objection is the least weighty. Witho
doubt the theory requires that the initial steps of
variation should also have selective value; otherwi
personal selection and hence germinal selection cot
not set in. Since, however, as I have before point
out, in no case can we pretend to a judgment regar
img the selective value of a modification, or have a

GERMINAL SELECTION. 61

experience -thereof, therefore the assumption that in
a given case where a character is transformed the
original initial steps of the variation did have selective
value, is not only as probable as the opposed assump-
tion that they had none, but is infinitely more probable,
for with this we can give an intelligible explanation
of the mysterious fact of adaptation, while with that
we cannot. Consequently, unless we are resolved to
give up all attempts whatsoever at explanation, we
are forced to the assumption that the initial steps of
all actually affected adaptations possessed selective
value.

The principal and fundamental objection that selec-
tion is unable to create 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 varia-
tions, but supposing merely that the groundwork
for favorable variations is present in the transforming
species, that is, supposing merely that in the consti-
tutional basis of the part to be changed are contained
components which render favorable variations possi-
ble 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 indi-
vidual cases, rendered intelligible in this manner, but
what is more difficult, we are able to understand the
Simultaneity of numerous and totally different modi-
fications of the most diverse parts co-operant towards

WW ay sos 3M) desi eee mie) ee: ae eee: alee Annese

62 GERMINAL SELECTION.

for example, in the simultaneous rise of instincts and
protective similarities, or in the harmonious and
simultaneous augmentation of two co-operant but in-
dependent 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 likeli-
\ hood 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 circum-
stances may vary differently, for example, the two
visual halves of soles; that homodynamic parts, (for
instance, the member-pairs of Arthropoda,) have fre-
quently varied alike, and not infrequently and in con-
‘formity with the needs of the animal, have varied dif-
ferently. It brings it about also that conversely species
of quite different fundamental constitutions occasion-
ally 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 diffi-
culties 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

GERMINAL SELECTION. 63

that have been recently brought forward by the acut-
est critics, as for example by Wigand, but particularly
by Wolff, find, as I believe, their refutation in this doc-
trine 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 attain-
able by changes of quantity, so far as that is at all pos-
sible for the organism in question.

Considering also the contrary process, the degenera-
tion of useless parts by the cessation of selection in re-
gard 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 ex-
tremity 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 de-
gree 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, most-
ly 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 under-
standing of observed transformations, particularly of

1“Beitrage zur Kritik der Darwin’schen Lehre,” Bio-

«re a.

64 GERMINAL SELECTION.

the degeneration of superfluous parts, that a her
of acquired characters would perform, without re1
ing necessary so violent an assumption. I have al
conceded that many transformations actually do
parallel to the use and disuse of the parts, that tl
fore it does really look as if functional acquisitio1
the individual life were hereditary. But if it be fi
that passively functioning parts, that is, parts w
are not alterable during the individual life by func
obey the same laws and also degenerate when the:
come useless, then we shall scarcely be able to r¢
our assent to a view which explains both cases,
certainly cannot be the physiological function w
provokes modifications in the individual, which
then subsequently transmitted to the germ and in
way made hereditary, if functionless parts also ch
when they become useless. It is precisely this use
ness, then, from which the initial impulse eman
and the primary modification is not in the soma
in the germ.

The Lamarckians were right when they mainta
that ‘the factor for which hitherto the name of nat
selection had been exclusively reserved, viz., pers
selection, was insufficient for the explanation of
phenomena. They were also right when they decl
that panmixia in the form in which until recent
held the theory was also insufficient to explain
degeneration of parts that had grown useless, but

* Poulton has adverted to the fact that this is neve
less not always the case; for example, it is not so wit!
teeth, whose shape it had also been sought to reduc
the mechanical effects of pressure and friction. See
Theory of Selection” in The Proceedings of the Boston
ciety of Natural History, Vol. XX., page 380. 1894.

GERMINAL SELECTION. 65

erred when they ascribed hereditary effects to the se-
lection-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 re-
quired 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. Con-
sequently, in all the divers orders of biological units
lying between the two extremes of biophores and
colonies, the modifications must be controlled by se-
lective 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 inter-
action. The three principal stages of selection, that of

66 GERMINAL SELECTION.

personal selection? as it was enunciated by Darwin and
Wallace, that of histonal selection as it was estab-
lished 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 sub-
stantiate in this article—these are the factors that have
co-operated to maintain the forms of Itfe in a constant
state of viability and to adapt them to their conditions |
of life, now modifying them pari passu with their en-
vironment, and now maintaining them on the stage
attained, when that environment is not altered.
Everything is adapted in animate nature? 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 selectior —

1As the highest stage of selective processes must be re-
garded that between the highest biological units, the colonies
or cormi—a stage, however, which is not essentially different
from personal selection. In this stage the persons enact the
part that the organs play in personal selection. Like their
prototypes they also battle with one another for food and in
this way maintain harmony in the colony. But the result of
the struggle endures only during the life of the individual
colony and can be transmitted through the germ-cells to the
following generation as little as can histological changes
provoked by use in the individual person. Only that which
issues from the germ has duration.

2 This statement has often been declared extravagant, and
it is so if it is taken in its strict literalness. On the other
hand, it would also seem, by a more liberal interpretation, as
if there existed non-adaptive characters, for example, rudi-
mentary organs. Adaptiveness, however, is never absolute
but always conditioned, that is, is never greater than outward
and inward circumstances permit. Moreover, an organ can

GERMINAL 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 in-
soluble,—it can be obtained only through the assistance
of this principle of the self-regulation of the originat-
ing 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 appar-
ent 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. Se-
lection of persons alone is not sufficient to explain the
phenomena; germinal selection must be-added. Ger-
minal selection is the last consequence of the applica-
tion of the principle of Malthus to living nature. It
js true it leads us into a terrain which cannot be sub-
mitted directly to observation by means of our organs
of touch and by our eyes, but it shares this disadvant-
age in common with all other ultimate inferences in
natural science, even in the domain of inorganic na-

only disappear gradually and slowly when it has become su-
perfluous; yet this does not prevent our recognising every
stage of its degeneration as adapted when compared with its
precursor. Further, it does not militate against the correct-
ness of the above proposition that there are also characters
whose fitness consists in their being the necessary accompani-
ments of other directly adapted features, as, for instance, the
red color of the blood.

68 GERMINAL SELECTION,

ture: in the end all of them lead us into hypothetical
regions. If we are not disposed to follow here, noth-
ing remains but to abandon utterly the hope of ex-
plaining 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 trans-
formation by adaptation to new, and by reversed adap-
tation to old conditions, the inequality of the sys-
tematic 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 some-
thing 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 con-
tradiction 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 arte-

sian well if he who bores will only drive undaunted
his drill into their depths.

APPENDIX.

I. THE REJECTION OF SELECTION.

Many years ago Semper? denied the power of se-
lection to create an organ, declaring that the organ
must have previously existed before selection could
have increased and developed it. More recently
Wolff? has distinguished himself by the vigor with
which he has attacked the “task” of “setting aside the
dogma of selection.” Henry B. Orr? 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,* in his recent voluminous but
in many respects excellent work, regards natural selec-
tion 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

1 Semper, Die natiirlichen Existenzbedingungen der Thiere,
Leipsic, 1880, pp. 218-219.

2 Wolff, “Beitraige zur Kritik der Darwin’schen Lehre,”
Biolog. Centralblatt, Vol. X., Sept. 15, 1890, and “Bemerkungen
zum Darwinismus mit einem experimentellen Beitrag zur
Physiologie. der Entwicklung,” Biolog. Centralblatt, Vol.
XIV., Sept. 1, 1894.

3 Henry B. Orr, A Theory of Development and Heredity,
New York, 1893.

4 Yves Delage, La structure du protoplasma et les théories
sur Vhérédité et les grands problémes de la biologie générale,
Paris, 1895.

69

70 APPENVIX.

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,! 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 Tiibingen Pro-
fessor 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.”
The lack of confidence latterly placed in the theory
of selection even by professed adherents of the doc-
trine, is well shown by such remarks as the following

1Henslow, The Origin of Species Without the Aid of
Natural Selection, A Reply to Wallace. 1804.

21f any one should deem these words too severe, let him
read the sarcastic passages in which Eimer has dispatched the
late unfortunate Eric Haase who had been presumptuous
enough to oppose the Tiibingen Professor’s deliverances on
certain points. Haase, as we all know, fell a victim to the
climate of the tropics, shortly after resigning the post of
Director of the natural science collections in Bangkok, in
order to return to Germany and to work out the fruits of his
tropical sojourn. The unfortunate end of this accomplished
man who had rendered important services to science had no
effect in‘mollifying the resentment of Herr Eimer at the op-
position which his views had encountered; and in twenty
printed pages he takes him to task in the most personal and
rancorous manner for this affront, remarking at the close:
“In the meantime Herr Haase has died. Nevertheless I owe

APPENDIX. 71

from Emery,1 who says: “Some pupils of Darwin
have gone beyond their master and discovered in nat-
ural selection the sole and universal factor control-
ling 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 Darwin-
ian, 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 com-
binations 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 for-
mation and discharge of explosive substances. Un-
stable combinations are upon the application of a

it to myself, in spite of this occurrence, to make public the
foregoing facts, in order,” etc. Any one who is interested in
knowing the motives of Herr Eimer’s exctise may find them in
his book Artbildung und Verwandtschaft bei den Schmetter-
lingen, Part IL., p. 66.

1“Gedanken zur Descendenz- und Vererbungstheorie.”

Biolog. Centralblatt, July 15, 1893.
2C, Lloyd Morgan, Animal Life and Intelligence, London,

1890-1891, Pp. 30-33-

72 APPENUIA.

stimulus suddenly disintegrated into simpler and more
stable compounds; through this disintegration they
evoke what is called the function of the disintegrat-
ing part—for example, certain changes of form (mus-
cular contractions) or the excretion of the disinte-
grated 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 aug-
menting delicacy of operation of physiological sub-
stances 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 varia-
tions.

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 be-
fore in an article published in the American Journal
of Science, Vol. XLVIII., for November, 1894, en-
titled “On Variations and Mutations.” Following the
precedent of Waagen and Neumayr, Scott sharply dis-
criminates between the inconstant vacillating varia-—
tions which it is supposed [?] produce simultaneously
occurring “varieties,” and “mutations,” or the suc-
cessively evolved time-variations of a phylum, which
constitute the stages of phyletic development. The
facts on which this view is based are those already

APPENDIX. 73

adduced in the text—the Zielstrebigkeit (to use K. E.
von Bar’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, how-
ever slowly, is not suggestive of many trials and fail-
ures 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 af-
fect 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 modi-
fication, and its occurrence in a large number of indi-
viduals.

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 un-
able 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 varia-
tions. 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 APPENDIX.

increasing distinctness and volume with every genera-
tion, 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 im-
possible, indeed, to see how considerable, that is per-
ceptible, 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 as-
sumption 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
paleontologists mentioned have been led to adopt, al-
though 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 conse-
quently 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 in-
dividual variations lie on the path of phyletic ad-
vancement 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

APPENDIX. 75

is, the actual resultant phyletic modification, permits
their being known as phyletic or as vacillating varia-
tions. Uncertain fluctuations along the path of evo-
lution 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, how-
ever, that these fluctuations are not a logical conse-
quence 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 act-
ing 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 perislr as being unfit to live, is
certainly correct in its ultimate foundations. But it is
in need of far more radical refinement than it under-
went in the hands of Empedocles, or than it seems
likely to undergo at the ands of many contemporary
inquirers. We know now that nature did not produce
isolated eyes, ears, arms, legs, and trunks, and after-
wards 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 in-
finitely far removed from its prototype, in the ques-
tion as to where all the non-adaptive individuals are
preserved that have perished in the struggle for exis-
tence and been eliminated from development by
selection? Where, for example, are the fossil remains

76 APPENDIX.

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 accom-
plish 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 ut-
most 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 diffi-
culties attending such a task as applied to the meagre
fossilic bones of prehistoric species, touching which the
richest discoveries never so much as remotely ap-
proach to the actual number of individuals that have
lived together for a single generation in the same hab-
itat. If the differences between good and bad in a
single generation were striking enough to be imme-
diately remarked as such in fossil bones, the develop-
ment 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 pro-

APPENDIX. 77

ceeding in the direction of adaptive growth, it is re-
markable 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.

Allusions to a connexion between the direction
of variation and the selective processes are to be found,
but they remained unnoticed or undeveloped. I have
been able to find at least two such observations, but
would not wish to assert that there are not more of
them hidden somewhere in the literature of the subject.
One of them is old and comes from Fritz Miller. It
was appended by his brother Hermann as a “Supple-
mentary Remark” to his book Die Befruchiung der
Blumen durch Insecten (1873) and is dated Novem-
ber 24, 1872. We read there: ‘My brother Fritz
Miller communicates to me in a letter which reached
my hands only after the bulk of the present work had
passed through the press, the following law discovered
by him, which materially facilitates the explanation by
natural selection of the pronounced characters of
sharply distinguished species: “The moment a choice
in a definite direction is made in a variable species,
progressive modification from generation to genera-
tion in the same direction will set in as the result of
this choice, wholly apart from the influence of ex-
ternal conditions. Transformation into new forms is
thus greatly facilitated and accelerated.’ ”

The facts on which F. Miller based the enunciation
of his law, are the results of several experiments with
plants, the numbers of whose grains (maize), or styles,
or flowering leaves, were; by the exercise of choice in
the cultivation, made to change in definite directions.
Accurately viewed their significance is the same as
that of numerous other cases of artificial selection, for

78 APPENDIX.

example, that of the long-tailed Japanese cock which
was laid at the foundation of the theory in the text,
although the numerical form of the observation gives
more precision and distinctness to the reasoning based
on them, than is to be observed in cases where we
speak of characters as being simply “longer” or
“shorter.” z

F. Miiller’s opinion regarding the increase of char-
acters by selection is expressed as follows: “The
simplest explanation of these facts appears to be that
every species possesses the faculty of varying within
certain limits; the crossing of different individuals,
so long as no choice is effected in a definite direction,
maintains the mean round which the oscillations take
place at the same points, and consequently the ex-
tremes also remain unaltered. If, however, one side
is preferred by natural or artificial selection, the mean
is shifted in the direction of this side and accordingly
the extreme forms are also displaced towards that side,
going now beyond the original limit. However, this
explanation does not satisfy me in all cases.”

It is not known to me that F. Miiller ever returned
to this conception subsequently to the year 1872 or
gave further developments of the same, nor have I
been able to discover that it has been mentioned by
other writers or incorporated in previous notions re-
garding selection.

The second naturalist who has approached the fun-
damental idea of my doctrine of germinal selection, is
a more recent writer. I refer to the English botanist
Thiselton-Dyer, a scientist whose occasional utterances
on the general questions of biology have more than
once evoked my sympathetic approval. In an article,
“Variation and Specific Stability,” which appeared in

APPENDIX. 79

Nature for March 14, 1895, this author enunciates
twenty theses touching this subject, many of which
appear to me apposite and correct, particularly the
following: In every species there is a mean specific
form round which the variations are symmetrically
grouped like shots around the bull’s eye of a target.
As soon as natural selection comes into play and
favors one of these variations it must shift the centre
of density. Variations arise by a change in the out-
ward conditions of life and can be useful or indiffer-
ent; only in the first case will natural selection obtain
control of them and “the new variation will get the
upper hand and the centre of density will be shifted.”
“ This is not germinal selection, but it is the same as
what I have referred to in this and in the preceding
essay as displacement of the zero-point of variation.
Thiselton-Dyer did not draw the conclusion that a
definitely directed variation answering to utility re-
sulted from this process, which variation alone must
cause the disappearance of useless parts, for the reason
that he never attempted to penetrate to the causes of
the shifting of the zero-point of variation. Neither
Fritz Miiller, whose utterances Thiselton-Dyer was ob-
viously ignorant of, nor Thiselton-Dyer himself pushed
his inquiries beyond the thought that the shifting in
question resulted entirely in consequence of personal
selection. There is no gainsaying that the degenera-
tion of useless organs cannot be explained by personal
selection alone, seeing that though the minus varia-
tions may possibly have a selective value at the be-
ginning of a degenerative process, they certainly can-
not have such in the subsequent course of the same,
when the organ has dwindled down to a really mini-
mal mass of substance as compared with the whole

80 - APPENDIX.

body. Of what advantage would it be to the whale if
his hinder leg, now concealed in a mass of flesh and no
longer protruding beyond the skin, should still be
reduced one or several centimetres in size? (Spencer.)
If the minus variations have no selective value, how
can the upper limit of the variational field be con-
stantly displaced downwards, as actually happens?
It is unquestionable but something different from per-
sonal selection must come here co-determinatively
into play.

V. HISTORICAL REMARKS CONCERNING THE ULTIMATE
VITAL UNITS.

(For this Appendix which is marked “Appendix
V.” in the German edition of Germinal Selection see
the footnote at page 40.)

VI. THE INITIAL STAGES ME USEPHE MODIFICATIONS.

Tix characterising as “least” weighty: the old objec-
tion that. the variations are too small at the start to be
useful and to be selected, I find myself diametrically
opposed to many writers of the present day, who have
taken up with renewed vigor this old stumbling block
to the principle of selection. Bateson? regards the
deficient proof of the utility of initial stages as the
most serious objection that can be made to natural se-
lection. New organs must in the necessity of the case
have first been imperfect; how, then, could they have
been selected since imperfect organs cannot be useful?
Answers from various quarters have already been

1 Materials for the Study of Variation with Especial Re-
gard to Discontinuity in the Origin of Species, London, 1895,
p. 16.

APPENDIX. 81

made to this and to similar objections, and Darwin
himself has referred to the fact that even the smallest
variations may have selective value; Dohrn, too, has
urged his principle of change of functions, which with
regard to this question of the utility of initial stages
has certainly a wide significance. Still, every trans-
formation and new structure in the narrow sense of
the word does not rest on change of function, and
neither Darwin nor Wallace, nor any other more re-
cent champion of the principle of selection, can ever
succeed in demonstrating in every case the selective
value of an initial stage. One reason why this cannot
be done is because in no case of morphological varia-
tion do we really know what these initial stages are.
To say that “new organs were at first necessarily im-
perfect” appears obvious enough, but it is at bottom a
meaningless assertion, for it is not only possible but
certain, that “imperfect” organs may still have selec-
tive value, and in by far the most cases have had se-
lective value. The fact that we see to-day a long grad-
uated line of forest-butterflies which possess resem-
blance to leaves and by this means are able in a meas-
ure to conceal themselves from prying eyes, yet that
this resemblance in many species is very imperfect, in
others more perfect, and in a very small number very
perfect, simply proves that even “imperfect” forma-
tions may be of utility. The word “imperfect” in this
connexion is itself very imperfect, for it is utterly an-
thropomorphic and estimates the biological value of a
structure by our own peculiar artistic notions of its
faithfulness to a leaf-copy, whilst we are really con-
cerned here only with its protective value for the
species in question, which is by no means dependent
merely on the faithfulness of the copying, on the faith-

84 APPENDIX.

finitely directed variation” from internal causes and of
a summation of “accidental” variations. He says:
“A summation of entirely accidental variations in a
given direction is extremely difficult,” because “natural
setection thus always awaits its fortune at the hands
of accident whereby it is possible that the little good
thereby produced will be swept away by other accidents
(disadvantages of position) or obliterated in the fol-
lowing generations by unfortunate crossings.” We
can, therefore, continues Emery, well conceive “how
many scientists look upon the whole theory of selection
as a fable, or else throw themselves into the arms of
Lamarckism.” Unquestionably Emery has here
singled out the insufficient points in the assumption of
a selection of “accidental” variations; he has recog-
nised the necessity of operating, not with single varia-
tions, but with “directions of variation.” He has not,
however, attempted the derivation of directed ten-
dencies of variation from known factors; he apparently
thinks of them as of something which has sprung from
unknown constitutional factors and consequently
ascribes to them the capacity of shooting beyond their
mark, so to speak, that is, of acting beyond and ahead
of utility, and so of producing modifications which may
lead to the destruction of the species.

INDEX.

Accidental variations, 1, 83.

Acquired variations, 33.

Acracids, 19.

Acrza, 52.

Active selection, 38.

Adaptations, 1, 10, 22, 61, 82.
. Adaptiveness, 66 footnote, 67, 74 et
"seq.

Ageronia, 19.

Anza, 22.

Aunlagen, 35, 47, 53-

Arthropoda, 52, 62.

Articulata, 30.

Artificial selection, 33.

Askenasy, 24, 60, 82.

Atoms, 57, 58.

Bar, K. E, von, 73.

Bateson, 18, 73, So.

“ Better"? individuals, 76,

Biology, character of research in, 7.
Biophores, 40, 47, 58.

Boltzmann, 4, 5.

Bonnet, 53-

Bourne, footnote, 54.

Briicke, 40.

Bnuiterflies, 14 et seqg., 18 et seq., SI.

Catonephele, 50.

Chance, 61.

Chemical selection, 71.
Chitons, 28.

Coadaptation, 30.

Colorings, protective, 14 et seq.
Constancy of species, 46.
Constructs, 8.

Cormi, 66 footnote.
Correlation, 21.

Danaids, 19.

Darwin, 11, 25, 29, 36, 38, 66, 81, 83.

Definite variation, 3, 4, 60, 76-79, 82.

Degeneration, 30 et seq., 39 et seq.
55» 63, 64, 79.

Delage, Yves, 40, 69.

Determinants, 6 et seq., 10, 36 et seq
42, 54, 58.

Developmental mechanics, 8, 9.

De Vries, 40.

Dimorphism, 58.

Directions of variations, 83.

Directive forces, 23, 24.

Dixey, 51 footnote.

Dohrn, 81.

Driesch, Hans, 12.

Dyer, Thiselton, 78-79.

Eimer, 16, 70.

Emery, 71, 83-84.

Empedocles, 75.

Epigenesis, 53 footnote, 58, 59.

Euploids, 19.

Europeans, exempt from malarial
fevers, $2.

Eurypheme, 22.

Evolution, 53 footnote, 59.

Fireworks, determinants and ids
compared to, 7.

“Fits,’’ 6 footnote.

Fluctuations of development, 74-75.

Formative laws, 17 et seq., 23.

Frog, I4.

Functional adaptation, 29.

Functionless parts, 64.

Galton, 36.
Germs, 7 et Seq., 40 et Seq.

86

Germinal selection, 1, 39, 44, 50-53,
59, 63, 66-68.

Germinal substance, 55 et seq.

Germ-plasm, 9, 44, 57.

Haase, Eric, 70.

Heliconids, 19, 20, 51 footnote.
Henslow, G., 70, 82.

Heredity, 4 et seq.

Hertwig, O., 54 footnote, 58, 59.
Hertz, 5, 6.

Histonal selection, 66.

Huxley, Thomas, 12.

Hypna, 22. r

Hypotheses, nature of, 5 et seq.

Ids, their theoretical character, 7.

Imagination, its function in science,
4

“Imperfect” formations, 81.

Individual variations, 73 et seq.

Inertia, law of organic, 15.

Internal forces of evolution, 16, 23,
24, 31, 60, 82-84.

Intrabiontic selection, 29.

Ishikawa, Professor, 34.

Japanese cocks, long-tailed, 34, 44,
7. :

Kallima, 22, 23, 50.

Katagramma, 22.

Knowledge, its character, 5.

Lamarckian principles, 24, 29 et seq.,
31 et seq., 38, 63-64, 68, 84.

Leaves, imitated by butterflies, 20 et
seq.

Locomotive, simile of, rr.

Malthusian principle, 65, 67.
Markings, butterflies’, 16 et seq.
Maxwell, 4, 5.

Mean of variation, 78-79.
Meristic, 18.

Mimicry, 19, 51 et seq.

Minot, S., 54 footnote.

Models, mental, 4 et seq.
Molecules, 58.

Morgan, Prof. C. Lloyd, 32, 71, 83.
Miller, Fritz, 77-79.

Miller, Hermann, 77.

INDEX.

Mussels, 28,
Mutations, 31 footnote, 72-76,

Nageli, 4, 11, 24, 60, 82.
Neumayr, 72.

| Newton, 5. 2

Nutrition of determinants, 36, 37, 41
47.
Nymphalide, 21.

Ontogenesis, 8,

Orr, Henry B., 69.
Osborn, Prof. H. F.; 33.
Owen, Richard, 11.

Paleontology, 31, 73, 75, 76.

Palms from Cordilleras, 82,

Pangenes, 40. _

Panmixia, 15, 39, 42, 43; 64.

Papilio, 16, 52.

Parallecta, 23.

Parts, struggling of the, 29, 39, 66-67.

Passively functioning parts, 30 et
seq., 64.

Personal selection, 30, 41, 42, 45, 52
64-66, 80.

Phyletic variation, 31-32 footnote.

Phylogenesis, 8.

Phylogenetic variations, 31-32, 73.

Plasomes, 40.

Plus and minus variations, 35, 42, 46,

50, 79-80.

‘Polymorphism, 58.

Poulton, 64 footnote.
Predestined variation, 4.
Pre-established harmony, 25.
Preformation, 53.

Protective colorings, 14 et seq.
Protogonius, 22.

Pseudocrza, 52.

Qualitative modifications, 46.
Quantitative changes, 46-47.

Retrogressive development, 38.
Round-worms, eggs of, 28.
Roux, Wilhelm, 29, 39, 65, 66.

Salamis, 22.
Scott, Prof. W. B., 31 footnote, 72-74.
Segmentation, 10,.

INDEX. 87

Selection, natural, 10, 25 et seq., 50,
51, 67, 69-73, 81, 82.

Selective value of variations, 60.

Semper, 69.

Siderone, 22,

Snails, 28.

Spencer, 14, 28, 29, 40, 53, 56, 80.

Struggle for existence, 65.

Survival of the fit, 52.

Symphzedra, 22.

Tabula rasa, W7, 24.

Tegetmeier, W. B., 34.
Teleological principles, 10, 16, 25.
Theories, nature of, 5 et seq.
Turbellaria, 28.

Units, vital, biological, physiological,
etc., 8, 40, 41, 53, 56, 65, 80.

Useful modifications, value of initial
stages of, 80-82,

Utility, 11, 18, 33, 45, 48, 62, 63, 82.

Variations, necessary, their constant
presence, 26 et seq., 31 et Seq., 61;
generally, 3, 11-14, 61, 71 et seq.

Waagen, 72.

Wallace, 11, 25, 29, 51, 66, 81.

Weldon, 36.

Whale, hind leg of, 42, 56, 80,

Whitman, C. O., 53.

Wiesner, 40.

Wigand, Albert, 11, 63.

Wings of butterflies, 14 et seq., 47-52,
56.

Wolff, K. F., 53, 62, 63, 69.

‘‘Worse"’ individuals, 76.

Zero-point of variation, 36 et seq
45; 74) 79+

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