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
Mueller. It was appended by his brother Hermann as a "Supplementary Remark"
to his book _Die Befruchtung der Blumen durch Insecten_ (1873) and is dated
November 24, 1872. We read there: "My brother Fritz Mueller 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 generation in the same direction will set
in as the result of this choice, wholly apart from the influence of
external conditions. Transformation into new forms is thus greatly
facilitated and accelerated.'"
The facts on which F. Mueller 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} 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."
F. Mueller's opinion regarding the increase of characters 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 extremes
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. Mueller 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 regarding selection.
The second naturalist who has approached the fundamental 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 {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 outward conditions of life and can be
useful or indifferent; 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 resulted 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 Mueller, whose utterances
Thiselton-Dyer was obviously 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 degeneration of useless organs cannot be explained by personal
selection alone, seeing that though the minus variations may possibly have
a selective value at the beginning of a degenerative process, they
certainly cannot have such in the subsequent course of the same, when the
organ has dwindled down to a really minimal mass of substance as compared
with the whole {80} 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 constantly displaced downwards,
as actually happens? It is unquestionable but something different from
personal 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 OF USEFUL MODIFICATIONS.
In characterising as "least" weighty the old objection 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[33] regards the deficient proof of the utility of initial stages as
the most serious objection that can be made to natural selection. 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 {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 transformation 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 recent 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 variation do we really know what these initial
stages are_. To say that "new organs were at first necessarily imperfect"
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
selective value, and in by far the most cases have had selective value. The
fact that we see to-day a long graduated line of forest-butterflies which
possess resemblance to leaves and by this means are able in a measure 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" formations may be
of utility. The word "imperfect" in this connexion is itself very
imperfect, for it is utterly anthropomorphic 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 concerned 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 {82}
faithfulness of the imitation, but on numerous other factors, such as the
frequency and sharp-sightedness of the enemies of the species, the
fertility of the species, their frequency and persecution in earlier
developmental stages, and so forth, in brief, on their need of protection
on the one hand and on their other means of protection on the other.
Now all this cannot be exactly calculated in any given case, and it will be
better, instead of haggling about individual cases concerning which we can
never judge with certainty, to take the position adopted in the text and
say: Since the utility of the initial stages _must_ be assumed unless we
are to renounce forever the explanation of adaptation, let us then take it
for granted. No contradiction of facts is involved in this assumption; in
fact, even individual variations exist whose eventual utility can be
demonstrated, for example, the invisible differences enabling Europeans of
certain constitutions to resist the attacks of tropical malarial
fevers,--or the differences of structure, likewise not directly visible,
which enable palms from the summits of the Cordilleras to withstand our
winter climate better than palms of the same species from along the
base-line of the mountains; and so on.
* * * * *
VII. THE ASSUMPTION OF INTERNAL EVOLUTIONARY FORCES
Definite variation was not only postulated in the last decade by Naegeli
and Askenasy, but has also been repeatedly set up in recent years by
various other authors. The Rev. George Henslow, in his book _The Origin of
Species Without the Aid of Natural Selection_, 1894, regards the variations
occurring in the state {83} of nature as always definite and not with
Darwin as indefinite, and meets the objection that modification but not
adaptation to outward conditions of life can be inferred from this fact, by
the bold assumption that it is precisely the outward conditions of life or
the environment which "induces the best fitted to arise." He further
concludes that natural selection has nothing to do with the origin of
species. At the basis of his conviction lies the naturally correct view
that the summation of _accidental_ variations is insufficient for
transforming the species, but that definitely directed variation is
necessary to this end. But concerning the way in which external conditions
are always able to produce the fit variations, he can give us no
information--if I am not mistaken, for the simple reason that such is not
the fact, that the outward conditions only apparently determine the
direction of variations whilst in truth it is the adaptive requirement
itself that produces the useful direction of variation by means of
selectional processes within the germ.
C. Lloyd Morgan also has recently expressed himself in favor of the
necessity of definite variation, though likewise without assigning a basis
for its action, and without being able to show how its efficacy is
compatible with the plain fact of adaptation to the conditions of life. He
seeks to find the origin of variation in "mechanical stresses and chemical
or physical influences," but this conception is too general to be of much
help. He has, in fact, not been able to abandon completely the heredity of
acquired characters.
Emery[34] likewise sees only the alternative of a {84} "definitely 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 selection 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 following 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 recognised the necessity of
operating, not with single variations, but with "directions of variation."
He has not, however, attempted the derivation of directed tendencies 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.
* * * * *
{85}
INDEX.
Accidental variations, 3, 83.
Acquired variations, 33.
Acracids, 19.
Acraea, 52.
Active selection, 38.
Adaptations, 3, 10, 22, 61, 82.
Adaptiveness, 66 footnote, 67, 74 et seq.
Ageronia, 19.
Anaea, 22.
_Anlagen_, 35, 47, 53.
Arthropoda, 32, 62.
Articulata, 30.
Artificial selection, 33.
Askenasy, 24, 60, 82.
Atoms, 57, 58.
Baer, K. E. von, 73.
Bateson, 18, 73, 80.
"Better" individuals, 76.
Biology, character of research in, 7.
Biophores, 40, 47, 58.
Boltzmann, 4, 5.
Bonnet, 53.
Bourne, footnote, 54.
Bruecke, 40.
Butterflies, 14 et seq., 18 et seq., 81.
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, 82.
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, 14.
Functional adaptation, 29.
Functionless parts, 64.
Galton, 36.
Germs, 7 et seq., 40 et seq.
{86}
Germinal selection, 3, 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.
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, 82-4.
Intrabiontic selection, 29.
Ishikawa, Professor, 34.
Japanese cocks, long-tailed, 34, 44, 78.
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, 11.
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.
Mueller, Fritz, 77-79.
Mueller, Hermann, 77.
Mussels, 28.
Mutations, 31 footnote, 72-76.
Naegeli, 4, 11, 24, 60, 82.
Neumayr, 72.
Newton, 5.
Nutrition of determinants, 36, 37, 41, 47.
Nymphalidae, 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, 64-86, 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.
Pseudocraea, 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.
{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.
Symphaedra, 22.
_Tabula rasa_, 27, 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.
* * * * *
Notes
[1] _Neue Gedanken zur Vererbungsfrage, eine Antwort an Herbert Spencer._
Jena. 1895.
[2] See Boltzmann, _Methoden der theor. Physik_, Munich, 1892. (In the
Catalogue of the Mathematical Exhibit.)
[3] Of late this saying of Newton's is frequently quoted as if Newton were
a downright contemner of scientific hypotheses. 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 gravitation, of whose character Newton could form no
conception and hence was unwilling to construct hypotheses concerning it.
Indeed, such a wholesale repudiation of hypotheses 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 Principia
Mathematica_, second edition, 1714, page 484.
[4] H. Hertz, _Die Principien der Mechanik_.
[5] Hans Driesch, _Die Biologie als selbststaendige Grundwissenschaft_,
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."
[6] _Die Allmacht der Naturzuechtung._ A Reply to Herbert Spencer. Jena,
1893, p. 27 et seq. [Also in the _Contemporary Review_ for September,
1893.]
[7] That is, by the law of exceedingly slow retrogression of superfluous
characters, which may be designated the law of organic inertia.
[8] _Materials for the Study of Variation with Especial Regard to
Discontinuity in the Origin of Species._ London, 1895.
[9] _Studien zur Descendenztheorie_, Leipsic, 1876. Vol. II. pp. 295 and
322.
[10] Compare my essay, _Neue Gedanken zur Vererbungsfrage_, Jena, 1895, p.
10, second footnote.
[11] On the same day on which the present address was delivered at the
International Congress of Zooelogists in Leyden, and on the same occasion,
Dr. W. B. Scott, Professor of Geology in Princeton College, New Jersey,
read a very interesting paper on the tertiary mammalian fauna of North
America, 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 variations 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 hereditary
variations, different _in origin_. Still it is likely that only a
relatively small portion of the numberless individual variations lie on the
path of phyletic advancement and so under 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.
[12] H. F. Osborn, "The Hereditary Mechanism and the Search for the Unknown
Factors of Evolution," in _Biological Lectures delivered at the Marine
Biolog. Lab. at Wood's Holl in the Summer Session of 1894_. Boston, 1895.
[13] In 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.
[14] _Neue Gedanken zur Vererbungsfrage_, Jena, 1895.
[15] Delage, in _La structure du protoplasma et les theories sur
l'heredite_, etc., Paris, 1895, is mistaken in attributing to Herbert
Spencer the merit of having first pointed out the necessity of the
assumption of biological units ranking between the molecule and the cell.
Bruecke set forth this idea three years previously to Spencer and
established it exhaustively in a paper which in Germany at least is famous
("Elementarorganismen," _Wiener Sitzungsberichte_, October 10, 1861, Vol.
XLIV., II., p. 381). Spencer's _Principles of Biology_ appeared between
1864 and 1868; consequently there can be no dispute touching the priority
of the idea. Strangely enough Delage cites Bruecke's essay in the
Bibliographical Index at the end of his book correctly, although Bruecke's
name and views are nowhere mentioned in the book itself. It is to be
observed, however, that the elementary organisms of Bruecke are not merely
the precursors of Spencer's "physiological 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 necessarily phenomena
of life. He aptly remarks on this point: "the physiological units of
Spencer are only chemical molecules 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, propagation, in short the
attributes of life, are not attributed by Spencer to his units, while
Bruecke by his very designation "elementary organisms" expresses the idea
of "ultimate living units," to use Wiesner's phrase. Of course this
particular aspect of the vital units was not emphasised by Bruecke with the
same distinctness and sharpness as by recent inquirers, who took up
Bruecke'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
Vries, and soon after by Wiesner, and subsequently by myself (De Vries,
_Intracellulaere Pangenesis_, Jena, 1889; Wiesner, _Die Elementarstructur
and 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'heredite_ 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, such an oversight is quite excusable.