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Vernon L. (Vernon Lyman) Kellogg.

Darwinism to-day; a discussion of present-day scientific criticism of the Darwinian selection theories, together with a brief account of the principal other proposed auxilary and alternative theories of species-forming online

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Online LibraryVernon L. (Vernon Lyman) KelloggDarwinism to-day; a discussion of present-day scientific criticism of the Darwinian selection theories, together with a brief account of the principal other proposed auxilary and alternative theories of species-forming → online text (page 29 of 38)
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inherited. On a host of data, derived from the pedigrees and
records of trotting horses and setter dogs, Redfield keenly works out
his inductions regarding the inheritance by young of the special
qualities due to training and practice (acquirement) of the parents;
that is, the best offspring (from the sportsman breeder's point of
view) come from the best trained parents. There is a great deal
of ammunition for the advocates of Lamarckism in Redfield's



3 o6 DARWINISM TO-DAY.

records, although his too sharp distinction between structural and
functional (so-called "dynamic") characters is not at all helpful.

The most recent serious treatment of the problem from the neo-
Lamarckian side, and one of great interest and real force, is that
Montgomery's of Montgomery in his book on "The Analysis of
explanation of Racial Descent in Animals" (1906). Montgomery
inheritance of contends that there can be no congenital variation,
Tariation. without external stimuli (or hybridisation) to initiate

it, because germ-plasm cannot be assumed to set up change inde-
pendently and automatically, as this would be almost like the
assumption of spontaneous generation. Montgomery says, "When
the process of heredity proceeds unchanged the ontogeny of one
individual is just like that of its parent. When a change of the
ontogeny occurs, so that the offspring comes to be different from
its parent, we say that a variation has appeared in the offspring.
This variation, it is thinkable, may have been produced: (i) by
internal growth energies, (2) by external environmental influences,
or (3) by a combination of both; and it is necessary to discuss
which one of these is the most probable.

"There is clearly, in the process of production of variation and.
mutation, some modification of the normal process of heredity.
Since in a number of species it has been shown that all the adult
individuals from one locality are not exactly alike, but show meas-
urable differences in dimensions, colour, or some other character,
it follows that the hereditary process of each such individual must
vary correspondingly, even though the variation does not become
perceptible until the stage of maturity. The origin of inherited
variation or mutation is then a question of the origin of modifica-
tion of the hereditary process.

"The regularity of the process of heredity is quite comprehensi-
ble on the basis of the direct transmission of definite chromosomes
in number, form, and quality constant for the species. From cell
to cell, from individual to individual, these chromosomes are regu-
larly transmitted in a continuous progress, therefore a succession of
similar individuals is quite understandable. One germ-cell comes
from a preceding one, to our knowledge is never formed from a
specialised tissue-cell, so that there is an uninterrupted passage of
the germ-plasm through the race. This is Weismann's idea of the
continuity of the germ-plasm, which we will paraphrase as the
continuity of the chromosomes.

"A variation to become inherited must then be referable to a
modification of the energies of this germ-plasm. The germ-plasm
is living substance of proved great importance in the metabolism of
the cell. Though in a sense it appears, from microchemical re-



OTHER THEORIES OF SPECIES-FORMING. 307

searches, to be the chief agent in constructive processes of the cell,
it equally appears to be incapable of life, or unable to act in a
normal manner, when removed from the influence of other cell
substances. The food required by a germ-cell for its growth is
obtained from without the cell, and must pass through the cytoplasm,
in more or less changed condition, to reach the chromatin within
the nucleus and there be elaborated into living substance and
passed over to the cytoplasm in other form. This conclusion is
drawn from both experimental and microchemical studies. So the
.oxygen required by the cell, and the water, must be obtained from
without the cell. This is simply in agreement with the general
principle that no body can increase in mass, circumambient condi-
tions remaining unchanged, without accretions from outside.
Therefore, the germ-plasm does not so much create new substances
as it changes substances brought to it. It and the other cell con-
stituents are harmoniously and mutually interdependent, and the
ultimate source of energies of these substances, all connected with
the elaboration of living matter, is referable to external agencies
because referable to food.

"This being the case, the energies of the hereditable substance,
the germ-plasm, are clearly dependent upon influences of the envi-
ronment. This conclusion is not at all in contradiction with the
idea of the continuity of the chromosomes, as we pointed out in
the preceding chapter. Therefore, Weismann was in error when, to
support his idea of the continuity of the germ-plasm, he at first
argued the energies of the germ-plasm to be independent of body
cells and of the environment generally. His supposition was both
unnecessary for the view of the continuity, and also out of agree-
ment with the phenomena. The ovum cannot elaborate its yolk
substance except out of food substance received from without ;
the amount of its food substance will depend upon the state of
nutritive metabolism of the individual carrying the egg-cell ; starva-
tion of that individual will cause cessation of energy in the germ-
cell, and ligaturing of the blood-vessels supplying the ovary will
produce death of the egg-cells. The results of observational expe-
rience teach that the germ-plasm is not a little god, capable of self-
existence without respect to external agencies, but is very intimately
bonded to the latter. Whether the germ-cell, as in the sponges, be
an amoeboid cell which wanders about in the body tissues, or
whether it is immovably held in place by tissue-cells, it is impossi-
ble that it can live and grow without receiving and reacting to
stimuli from these tissue-cells. The egg-cells of many animals are
set free in water before they commence to cleave into embryonic
cells; how can we say, then, that the conditions in the water do



3 o8 DARWINISM TO-DAY.

not influence them? They will die if removed from the water, and
develop abnormally if certain substances be added to or subtracted
from the water. But the embryonic differentiation is a result of
chromosomal activities, as we have seen; therefore, changes in the
medium must influence the germ-plasm. Is not a well-recognised
characteristic of living matter, response to external stimuli? How
can any living cell be acted upon by stimuli and yet not react to
them? There is not a single observation to show that any germ-
cell, or its germ-plasm, is in any way guarded or protected from
external stimuli, either by the structure of its cell wall or peripheral
cytoplasm, or by the nature of the living tissue that encloses it.
And whatever affects the cell body must indirectly affect the
chromosomes, because of the physiological connection of the two.

"From such considerations it would seem practically certain that
the energies of the chromosomes are to some extent respondent to
environmental stimuli. And since observation shows that living
matter responds differently, if not always according to the nature
of the stimulus at least to its degree, it would follow that change in
the nature or degree of the environmental agencies would indirectly
engender change in the activities of the germ-plasm. Not to admit
this would be to deny to the germ-plasm, without empirical reason,
properties proven for all other living substances.

"This thought had long ago been expressed clearly, though from
a different line of reasoning, by Spencer (1865). We may state it
in another way. Tissue-cells are granted by experimental physiolo-
gists the ability of different response, or different intensity of
response, to stimuli of different kind or degree. But a tissue-cell
is a lineal descendant of a germ-cell, and receives germ-plasm
from the latter. Now since the germ-plasm has been transmitted
continuously to the tissue-cell, must not the energies of the germ-
plasms of the two be alike at least in their general response
activity? Again, a Protozoan may be considered as a cell not
exactly correspondent to a germ-cell of a Metazoan, but as some-
thing more, as a unit with properties of both a germ-cell and a
tissue-cell, for its cytoplasmic differentiations (cilia, contractile
vacuoles, cytopharynx, etc.) are comparable to the soma of a Meta-
zoan. In the case of the Protozoan Paramcecium, Calkins (1904)
has shown that the reproductive activity is increased or diminished
according to the amount and kind of food stimuli. Here, then, a
Protozoan has its reproductive activities, therefore the energies of
its germ-plasm, profoundly influenced by environmental changes;
and it is primarily what we may term the germ-cell constituent of
the Protozoan that becomes influenced, that part which has to do
with reproduction of the individual. Weismann considered the



OTHER THEORIES OF SPECIES-FORMING. 309

Protozoan exactly comparable, in the sense of strict continuity of
reproduction, to the germ-cell of a Metazoan, and yet failed to
note that a Protozoan can be influenced by environmental change.

"Accordingly, an environmental change may be capable of induc-
ing change in the energies of the germ-plasm. The expression of
the energies of this substance, as viewed in temporal succession,
constitutes heredity. Therefore, the process of heredity may become
modified by a change in the environmental conditions of the germ-
plasm. And since we defined variation as a modification of heredity,
a variation could be produced by external influences acting upon
the germ-plasm, understanding by external influences influences of
the tissue-cells upon the germ-cells, or, in case the germ-cells are
not enclosed, influences of the non-living environment."

In a recent exhaustive paper by Tower, W. L., on "Evolution in
Chrysomelid beetles of the genus Leptinotarsa," Publication No. 48
of the Carnegie Institution of Washington, 1907, the author, although
on the whole a strong adherent of selection as the all-important
factor in species-forming, states specifically his belief, on the basis
of extensive observation and experiment, that external factors may
and do influence the germ-plasm to the extent of compelling it to
produce variations. These variations will not be photographic re-
productions of modifications of the soma, but they will be the vari-
ations which lie at the basis of species change. In other words,
Tower holds that variations are epigenetic in their origin, although
they are manifest as congenital differences. That is, acquired
characters in the usual sense of the term are not heritable, but all
variability is nevertheless due to the influence of environment. This
paper by Tower is a distinctly valuable contribution to our knowl-
edge of heredity and species change and it is based upon a large
amount of actual close observation and experiment.

In a recent paper by Jonathan Wright, "The Origin and Heredity
of Matter," in the St. Louis Medical Review, 1906, something of the
same attitude is taken, although the author is much more inclined
to the belief in the general heritability of acquired characteristics.
This short paper is an admirable treatment, based on a full acquaint-
anceship with the modern literature on the subject, of the problem
of heredity.

* See exposition of a number of these theories in appendix of
chapter viii of this book.

4 Haacke, W., "Grundriss der Entwicklungsmechanik," p. 289
ff., 1897.

6 Plate, L., "Uber die Bedeutung der Darwin'schen Selections-
prinzip," p. 218, 1903.

* The following account of the scientific aspects of Luther Bur-



3 to DARWINISM TO-DAY.

bank's work, which has attracted so much attention from evolu-
tionists and the world generally, was published by Kellogg, in the
Pop. Sci., Mo., Vol. LXIX, pp. 363-374, 1906.

"Mr. Burbank has so far not formulated any new or additional
laws of species-change, nor do his observations and results justify

Scientific anv suc ^ formulation, and we may rest in the belief

aspects of Bur- that he has no new fundamental laws to reveal. He
"bank's work. h as indeed the right to formulate, if he cares to, some
valuable and significant special conclusions touching certain already
recognised evolution factors, in particular the influence on varia-
bility of the two long-known variation-producing factors of hybridi-
sation and modification of environment. His reliance on the marked
increase in variability to be got after a crossing in the second and
third generations over that obvious in the first, will come as a sur-
prise to most men first getting acquainted with his work. He has
got more starts for his new things from these generations than in
any other way. He is wholly clear and convinced in his own mind as
to the inheritance of acquired characters ; 'acquired characters are
inherited or I know nothing of plant life,' he says ; and also con-
vinced that the only unit in organic nature is the individual, not
the species; that the so-called species are wholly mutable and de-
pendent for their apparent fixity solely on the length of time through
which their so-called phyletic characters have been ontogenetically
repeated. He does not agree at all with de Vries that mutations in
plants occur only at certain periodic times in the history of the
species, but rather that, if they occur at all, they do so whenever
the special stimulus derived from unusual nutrition or general
environment can be brought to bear on them. He finds in his
breeding work no prepotency of either sex as such in inheritance,
though any character or group of characters may be prepotent in
either sex. He believes that no sharp line can be drawn between the
fluctuating or so-called Darwinian variations and those less usual,
large, discontinuous ones called sports. Ordinary fluctuating varia-
tion goes on under ordinary conditions of nutrition, but with ex-
traordinary environmental conditions come about extraordinary
variation results, namely, discontinuous, sport or mutational varia-
tion. These variations are the effects of past environment also,
having remained latent until opportunity for their development
occurs. Starvation causes reversions, but reversions can also be
produced by unusually rich nutrition. New variations are developed
most often, as far as environmental influences go, by rich soil and
generally favourable conditions. So-called new qualities are usually,
if not always (the fact may sometimes net be obvious), simply
new combinations of old qualities, both latent and obvious. To get



OTHER THEORIES OF SPECIES-FORMING. 311

a new and pleasing odour it may often be sufficient simply to lose
one bad element in an old odour. So one might go on for some
pages with specific conclusions or deductions reached by Burbank
on a basis of experience. But it is true that he has at his command
the knowledge of no new fundamental scientific principles to give him
advantage over us. And yet none of us has done what Burbank
has been able to do, although many of us have tried. What then
is it that Burbank brings to his work of modifying organisms
swiffty and extremely and definitely that others do not?

"To answer this it will be advisable to analyse in general terms,
at least, the various processes which either singly, or in combina-
tions of two or three, or all together, are used by Mr. Burbank in
his work. We may roughly classify these processes and means.
First, there is the importation from foreign countries, through
many correspondents, of a host of various kinds of plants, some
of economic value in their native land and some not, any of which
grown under different conditions here may prove specially vigorous
or prolific or hardy, or show other desirable changes or new quali-
ties. Among these importations are often special kinds particularly
sought for by Burbank to use in his multiple hybridisations ; kinds
closely related to our native or to already cultivated races which,
despite many worthless characteristics, may possess one or more
particular, valuable ones needed to be added to a race already useful
to make it more useful. Such an addition makes a new race.

"Second, the production of variations, abundant and extreme, by
various methods, as (a) the growing under new and, usually, more
favourable environment (food supply, water, temperature, light,
space, etc.) of various wild or cultivated forms, and (b) by hybridi-
sations between forms closely related, less closely related and,
finally, as dissimilar as may be (not producing sterility), this
hybridising being often immensely complicated by multiplying
crosses, i. e., the offspring from one cross being immediately crossed
with a third form, and the offspring of this with still another form,
and so on. These hybridisations are made sometimes with very
little reference to the actual useful or non-useful characteristics of
the crossed parents, with the primary intention of producing an
unsettling or instability in the heredity, of causing, as Burbank
sometimes says, 'perturbations' in the plants, so as to get just as
wide and as large variation as possible. Other crosses are made,
of course, in the deliberate attempt to blend, to mix, to add together,
two desirable characteristics, each possessed by only one of the
crossed forms. Some crosses are made in the attempt to extin-
guish an undesirable characteristic.

"Third, there is always immediately following the unusual produc-



3I2 DARWINISM TO-DAY.

tion of variations, the recognition of desirable modifications and the
intelligent and effective selection of them, i. e., the saving of those
plants to produce seed or cuttings which show the desirable varia-
tions and the discarding of all the others. In Burbank's gardens
the few tenderly cared for little potted plants or carefully grafted
seedlings represent the surviving fittest, and the great bonfires of
scores of thousands of uprooted others, the unfit, in this close
mimicry of Darwin and Spencer's struggle and survival in nature.

"It is precisely in this double process of the recognition and selec-
tion of desirable variations that Burbank's genius comes into
particular play. Right here he brings something to bear on his
work that few other men have been able to do. It is the extraordi-
nary keenness of perception, the delicacy of recognition of desirable
variations in their (usually) small and to most men imperceptible
beginnings. Is it a fragrance that is sought? To Burbank in a bed
of hundreds of seedling walnuts scores of the odours of the plant
kingdom are arising and mingling from the fresh green leaves, but
each, mind you, from a certain single seedling or perhaps from a
similar pair or trio. But to me or to you, until the master prover
points out two or three of the more dominant single odours, the
impression on the olfactories is simply (or confusedly) that of one
soft elusive fragrance of fresh green leaves. Similarly Burbank
is a master at seeing, and a master at feeling. And besides he has
his own unique knowledge of correlations. Does this plum seed-
ling with its scores of leaves on its thin stem have those leaves
infinitesimally plumper, smoother or stronger, or with more even
margins and stronger petiole, or what not else, than any other
among a thousand similar childish trees? Then it is saved, for
it will bear a larger, or a sweeter, or a firmer sort of plum, or more
plums than the others. So to the bonfires with the others and to
the company of the elect with this 'fittest' one. Now this recogni-
tion, this knowledge of correlations in plant structure, born of the
exercise of a genius for perceiving through thirty years of oppor-
tunity for testing and perfecting it, is perhaps the most important
single thing which Burbank brings to his work that other men do
not (at least in such unusual degree of reliability). Enormous
industry, utter concentration and single-mindedness, deftness in
manipulation, fertility in practical resource, has Burbank and so
have numerous other breeders and experimenters. But in his per-
ception of variability in its forming, his recognition of its possi-
bilities of outcome, and in his scientific knowledge of correlations,
a knowledge that is real, for it is one that is relied on and built on,
and is at the very foundation of his success, Burbank has an
advantage of true scientific character over his fellow workers, and



OTHER THEORIES OF SPECIES-FORMING. 3 J 3

in it he makes a genuine contribution to scientific knowledge of
plant biology, albeit this knowledge is so far only proved to be
attainable and to exist. It is not yet exposed in its details and may
never be, however unselfish be the owner of it. For the going
to oblivion of scientific data of an extent and value equivalent, I
may estimate roughly, to those now issuing from any half-dozen
experimental laboratories of variation and heredity, is the crying
regret of all evolution students acquainted with the situation. The
recently assumed relations of Mr. Burbank to the Carnegie Insti-
tution are our present chief hope for at least a lessening of this
loss.

"But let us follow our saved plum seedling. Have we now to
wait the six or seven years before a plum tree comes into bearing
to know by actual seeing and testing what new sprt of plum we
have? No; and here again is one of Burbank's contributions (not
wholly original to be sure, but original in the extent and perfection
of its development) to the scientific aspects of plant-breeding. This
saved seedling and other similar saved ones (for from the exami-
nation of 20,000 seedlings, say, Burbank will find a few tens or
even scores in which he has faith of reward) will be taken from
their plots and grafted on to the sturdy branches of some full-grown
vigorous plum tree, so that in the next season or second next our
seedling stem will bear its flowers and fruits. Here are years saved.
Twenty, forty, sixty, different seedlings grafted on to one strong
tree (in a particular instance Burbank had 600 plum grafts on a
single tree!) ; and each seedling-stem certain to bear its own kind
of leaf and flower and fruit. For we have long known that the
scion is not materially influenced by the stock nor the stock by
the scion ; that is not modified radically, although grafting sometimes
increases or otherwise modifies the vigour of growth and the extent
of the root system of the stock.

"If now the fruit from our variant seedling is sufficiently desira-
ble ; if it produces earlier or later, sweeter or larger, firmer or more
abundant, plums, we have a new race of plums, a 'new creation' to
go into that thin catalogue of results. For by simply subdividing
the wood of the new branch, i. e., making new grafts from it, the
new plum can be perpetuated and increased at will. Simple, is it
not? No, it is anything but that in the reality of doing it; but in
the scientific aspects of it, easily understandable.

"Perhaps it may not be amiss to call attention to what must be
the familar knowledge of most of us, and that is the fact that many
(probably most) cultivated plants must be reproduced by division,
that is by cuttings, buds, or grafts, and not by seeds, in order to
grow 'true.' For a piece of a cultivated plant will grow out to be



314 DARWINISM TO-DAY.

very much like the individual it was cut from, but the seeds will
not, in most cases, reproduce faithfully the parents, but will pro-
duce a very variable lot of individuals, most of them strongly
reversionary in character. Grow peach trees from the stones of
your favourite peach and see what manner of peaches you get;
but if you want to be sure of more peaches like the ones you enjoy,
graft scions from your tree on to other trees. Indeed one of the
plant-breeder's favourite methods of making a start for new things,
of getting the requisite beginning wealth and eccentricity of varia-
tion, is to grow seedlings, especially from cross-bred varieties.
Burbank will give you a thousand dollars for a pinch of horseradish
seed. Sugar-cane seed is needed. The amelioration of many kinds
of fruit and flowers and vegetables is checked, because in our care-
lessness we have allowed these kinds to get into that condition of
seedlessness which almost all cultivated races tend toward when
grown from cuttings. In our oranges and grape-fruit and in a score
of other fruits, the elimination of seeds is exactly one 6f the modifi-
cations we have bred and selected for, in order to make the fruits



Online LibraryVernon L. (Vernon Lyman) KelloggDarwinism to-day; a discussion of present-day scientific criticism of the Darwinian selection theories, together with a brief account of the principal other proposed auxilary and alternative theories of species-forming → online text (page 29 of 38)