Copyright
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

. (page 18 of 38)
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 18 of 38)
Font size
QR-code for this ebook


present chapter, then, is mostly a continuation of the pres-
entation of "Darwinism Attacked" and "Darwinism De-
fended," which is given a separate place because of the
special character of the argument with which it has directly
to do, namely, the synthetic or theory-building side, instead
of the analytic or theory-destroying side, and because of
the probable advantage to the student and general reader
wishing to understand and compare the general character
and significance of the various new theories of species-
forming with whose names, such as heterogenesis, ortho-
genesis, metakinesis, geographic isolation, biologic isolation,
organic selection, or orthoplasy, he occasionally meets in his
187



!88 DARWINISM TO-DAY.

general reading. As directly continuing the last chapter we
may consider first those theories put forward, chiefly by
Darwinians, as auxiliaries or supports of the selection
theory. Then we may briefly take up those theories that
have been advanced, mostly in recent years, as more or less
nearly completely prepared to replace Darwinism as a suffi-
cient scientific causo-mechanical explanation of species-
forming and descent.

The Weismannian Theories of Panmixia and Germinal
Selection.* Weismann has for years been the most con-
spicuous of the neo-Darwinians, that is, of
portmt contritm- those who would free Darwinism from all taint
tioM to biology. o{ L arnarc id srn it should always be remem-
bered that Darwin was inclined to attribute some degree of
influence in species-forming to the Lamarckian factor of
the inheritance of individually acquired adaptive charac-
ters and to make selection the all-sufficient and, indeed,
sole factor in species-forming. His great services to biology
in general and to the clearer understanding of the problems
of heredity and descent in particular, are unquestioned and
unquestionable. His careful investigation and illumination
of the vexed question of the inheritance of acquired charac-
ters, his definitive exposition of that point of view which
distinguishes sharply in the individual between the germ-
plasm (that particular protoplasm in the body from which
the germ-cells, eventually new individuals, arise) and the
soma- plasm (that which develops into, or gives rise to, the
rest of the body), his development of the interesting and
suggestive combinations of fact and theory designated by
the phrase names "continuity of the germ-plasm" and "im-
mortality of the Infusoria," these products of his investi-
gating and philosophising mind prove him one of the ablest
of modern biological scholars. They also make him the
principal present-day champion of the selection theory. For
all these expositions of fact and theory are of a nature to>



OTHER THEORIES OF SPECIES-FORMING. 189

enhance the credit of selection and to discredit certain other
species-forming theories, in particular the only one, namely,
Weismann as Lamarckism, which, until recently, has been in
champion of any real sense a rival of Darwinism. Against
selection. Weismann then and against Weismann's re-

modelled kind of Darwinism, against his propaganda of the
>Allmacht of selection, the adherents of Lamarckism and the
critics of selection have turned their sharpest weapons. The
result of the struggle has been to compel Weismann himself
to say : "Although the principle of selection appears to solve
in simplest manner the riddle of the fitness (Zweckmassig-
keit) of all arising organisms (alles Entstehenden), yet it
appears ever more clearly in the course of the further inves-
tigation of the problem, that one cannot explain all with it,
at least in its original limitations (dass man mit ihm, in
seiner ursprungliche Beschrankung, wenigstens, nicht
ausreicht)."

To support the selection theory in two of its weakest and
most criticised places, Weismann has proposed two striking
auxiliary theories, namely, the Theory of Panmixia, to
explain the degeneration of functions and organs, and the
more recent Theory of Germinal Selection, to account
for the now practically generally admitted existence of
orthogenesis or determinate variation and evolutionary
progress along fixed lines even to the possible final dis-
advantage of the organisms involved, and to account for
the beginnings of variation and their maintenance until
sufficiently developed to serve as handles for selection. The
proposal by Weismann of the second theory, that of
germinal selection, was the practical admission on his part
of the impotence of selection to initiate new lines of develop-
ment or descent. It was a concession on Weismann's part
of the justness of the demand for an evolutionary factor to
explain the beginnings of lines of development, whether of
new organs or new species. And there is no doubt that it is



1 9 o



DARWINISM TO-DAY.



the most ingenious mechanical explanation yet offered of
the workings of such a factor. Indeed, Weismann, with
characteristic ingenuity and capacity, has offered the be-
lievers in orthogenesis that which they so far had not been
able to get for themselves, namely, a possible causo-mechan-
ical explanation of it. It should be noted that Roux's theory
of the battle of the parts (explained later) was a forerunner
of, and undoubtedly the suggestion for, the theory of
germinal selection.

Familiar to all students of biology, and certainly not
wholly unfamiliar to laymen, are those structures or parts
in the body known variously as vestigial struc-
anmMato^? tures > rudimentary or degenerate organs. The
plain vestigial vermiform appendix in man is one ; the eye of
the mole is another; the functionless wing of
the ostrich, the useless fore-feet of a milk-weed butterfly,
and the splint bones of the horse, are others. Almost every
animal kind possesses vestigial organs, and some kinds
possess very many. Those in the human body make an
amazingly long list. All these are organs, which have once
that is, in ancestors of the present particular organism
been well-developed and probably useful. But these
organs now are useless or even harmful. The human
appendix vermiformis is harmful; the tiny fore-feet of the
milk-weed butterfly are useless. Why do animals have
such vestigial organs ? Because they derive them by hered-
ity from ancestors. But in these ancestors the organs were
well developed and useful. How is it that the present
organisms do not need the same organs ? They have adopted
new habits, or live in a new environment, or have developed
other means of supplying the old want ; in a word the organs
are superfluous. How is it that the organs have become
thus degenerate or vestigial? This is the question that
selection has difficulty in answering satisfactorily. Selec-
tion can develop and specialise organs of use and advantage ;



OTHER THEORIES OF SPECIES-FORMING. 191

but how can it cause organs no longer useful and advan-
tageous to degenerate?

It is possible, perhaps, to explain the eradication of
positively harmful organs by a process of negative or
reversed selection. If an organ becomes actually harm-
ful because of a change in life conditions, individuals
with the organ in poorest, least energetically functioning
condition might be conceived to have an advantage and be
preserved by selection to pass on to their offspring this
less developed, i. e., rudimentary or vestigial, character of
the particular organ in question. But when the organ is
simply only rendered useless by the change in life condi-
tions, as when a species of fish or insect gradually comes to-
inhabit deep dark caves and thus has no more use for its
eyes, how does selection explain the degeneration ? It really
doesn't, satisfactorily. So Weismann offers the theory of
panmixia to account for it. This is, simply, that owing to
the cessation of selection in regard to the particular organ
whose function is rendered no longer advantageous or
necessary under the new life conditions that this cessation
of selection is an obvious result of such a state of affairs
was recognised by Darwin himself, and by other biologists
individuals born with this organ defective or in a condition
below the average, would not be necessarily killed by the
rigours of the intra-specific struggle, and would therefore be
as likely to mate and keep on producing offspring as the
ones with the organ in average or above average conditions.
This general participation of all kinds of individuals (all
kinds, that is, as regards the state of the particular organ)
in producing the next generation, and the continued repeti-
tion of this general mixing, panmixia, would obviously lead
to a reduction of the earlier high condition of development
of the organ. Weismann thinks, or thought, it would lead
to a steady degeneration of the organ. But few other biol-
ogists, even those ardent selectionists anxious to find in



I 9 2 DARWINISM TO-DAY.

panmixia an explanation not involving the admission of
any new organ-modifying factor, have been able to see how
panmixia can do more than simply reduce the organ to a
certain stage below the original state of greatest effective-
ness. By resorting to mathematics several writers have
determined the exact unfortunately for their convincing
character several degrees of reduction or degeneration that
will result from panmixia. The difficulty of explaining
degeneration (to the degree in which it is manifest in thou-
sands of known cases) on the basis of panmixia alone, is that
there is included no factor or influence that would sum up
or cumulate variations in a retrogressive direction any more
than in any other. The Darwinian variations of the use-
less organ would, by the law of error, simply keep the organ,
thus abandoned by selection, swinging about a mean but
little below the condition possessed by the organ at the time
of its abandonment. If the organ were large enough, or of
a character whereby it would entail a constant considerable
disadvantageous expense of food material to maintain it,
then selection might, on a basis of an advantageous economy
of living, tend to reduce it to a non-disadvantageous size or
character. But this disadvantage, although easily presumed
by carrying out the rigour of the struggle to a logical ex-
treme, cannot, in fact, and biologists on the whole admit
this, in common sense be assumed.

Lamarckism offers a perfectly simple and perfectly effect-
ive and satisfactory explanation of vestigial organs and the
modus of their degeneration. But to accept this

The Lamarck- , , . . . , .. T ,

ian explanation means to accept the basic principle of Lamarck-
of vestigial j sm namely, the inheritance of acquired char-

structures.

acters. And it is one of Weismann s most con-
spicuous positive achievements that he has demonstrated the
unproved character of this theory. Lamarckism says that
the first fishes to go into the dark cave suffered a partial
individual degeneration of their eyes through disuse and



OTHER THEORIES OF SPECIES-FORMING. 193

that this eye degeneration was inherited by their young,
whose eyes, already bad, suffered further degeneration in
their life-time through disuse, and that after comparatively
few generations this cumulative actual morphologic degen-
eration through disuse and we know that unused active
organs, as muscles, stimulus-perceiving parts, etc., do actu-
ally degenerate in an individual's life-time through disuse
would reduce the eyes to a very degenerate condition. Other
cases of degeneration, especially of passive organs (i. e.,
where the organ's condition was not so wholly a function
of use or disuse, but of the direct moulding influence of
extrinsic influences), are explained by Lamarckism on the
basis of the inheritance of the results of the direct action
or influence of environment on the organ. For example,
the gradual disappearance of pigment (blanching) charac-
teristic of many cave animals, would be explained by the
absence of the extrinsic factor, light, which is necessary to
stimulate pigment production.

In necessarily closing this all too brief reference * to
panmixia, it may be said that Weismann himself has in
recent years recognised its unconvincing character ; and that
Plate, a strong upholder of selection, in a most careful
weighing of panmixia, finds it capable of explaining func-
tional degeneration but not any actual considerable mor-
phological rudimentation.

The Theory of Germinal Selection was proposed by Weis-
mann in 1895, more definitively in 1896. Plate introduces
Weismann's *" s discussion of this theory as follows : "Its
theory of ger- aim is the rehabilitation of the selection princi-
minai selection. ple i t s h a ll overcome all objections and doubts
which have been raised against the selection theory and shall
act as the magician's wand to clear all difficulties from its
way. Its strength shall avail in four directions. First, it
shall explain how not only degeneration (physiological) but
rudimentation (morphological) occurs in panmixia; second,



194 DARWINISM TO-DAY.

why exactly those variations needed for the development of
a certain adaptation appear at the right time; third, how
correlation of adaptation comes to exist; and fourth, how
variations are able to develop orthogenetically along a defi-
nite line, without depending on the necessity of a personal
selection raising them step by step." Weismann himself
refers to the theory as "a spring of definitively determined
variation." In 1902, Weismann further applied the theory
to the explanation of monsters, and other cases of terato-
genesis, of "sports" (sudden or large discontinuous varia-
tions), of suddenly appearing sex-characters, of specific
talents, and still other heretofore unsatisfactorily explained
phenomena.

In defining the theory of germinal selection we come at
the very start to a difficulty based on the fact that little or
no reference has heretofore been made in this
and chemical book to certain various theories or speculations
Btrnctnre of as to the ultimate structure of protoplasm, espe-
cially the protoplasm of the germ-cells. In
recognising protoplasm as the "physical basis of life" (Hux-
ley's phrase), biologists have naturally tried to find in
its actual physical make-up some clue to its marvellous
capacities. The highest powers of our best microscopes,
however, reveal little more of this intimate physical struc-
ture than does our unaided eye. Probably the colloidal char-
acter of protoplasm, that is, its amorphous, non-crystalline,
viscous condition, is the most important physical fact about
it revealed by our closest examination. But this apparent
simplicity of physical structure is very unsatisfying to most
biologists, and they demand the assumption of an extremely
complex structure ; a subdivision of germinal protoplasm
into structural units and groups of units, just as the chemist
assumes, in his atomic theory, a subdivision of substances
into molecules and atoms. These protoplasmic units are,
of course, invisible ; like the atoms, they are beyond the see-



OTHER THEORIES OF SPECIES-FORMING. 195

ing of our microscopes. This nearly unanimous demand
on the part of biologists for a complex physical structure
of protoplasm, depends largely on the fact that our present
knowledge of the chemical constitution of protoplasm offers
absolutely no explanation of its capacities. We know that
protoplasm is composed of certain familiar elements, pres-
ent in certain proportions. But beyond that nothing; the
actual chemical relations of these component elements are
too complex for analysis. Besides, certain observations of
the processes of protoplasmic behaviour suggest strongly
the workings of a machine whose effectiveness lies in its
physical make-up. Finally, the phenomena of heredity I
seem to admit of no other explanation than the assumption I
of a composition of the germinal protoplasm out of myriads
of structural units actually representing the myriads of cells,
or groups of cells, of the fully developed body.

Ever since protoplasm has been recognised as the physical
basis of life, therefore, and ever since the germ-cells have
been recognised not to be miniature men and women, but,
as far as the eye and microscope go, masses of primitive
protoplasm differentiated only into cell-plasm, nucleus, and
nuclear parts (chromosomes, centrosomes, nucleoli, etc.),
there have been "atomic" theories of protoplasmic struc-
ture. Unfortunately for the standing of any one of these
theories, each working biologist seems to have made one
for himself, so that instead of one universally accepted,
hence usable and useful, atomic or unit theory such as the
chemists have and the modern physical chemists seem
to be rebelling even against that, biology has had a host
of protoplasmic unit theories of which the one we have here
specially to refer to is known as Weismann's theory of
biophors and determinants. Several of the better known or
more ingenious of these theories are outlined in very sum-
mary fashion in the appendix 4 of this chapter. What we
need now to know of biophors and determinants in order to



I9 6 DARWINISM TO-DAY.

understand the theory of germinal selection, is this : Weis-
mann conceives the protoplasm of the cell nucleus to be
composed of units called biophors these biophors can also
migrate out into the cytoplasm surrounding the nucleus
which are the bearers of the individual characters of the cell.
The total character of any cell, its form, make-up, and spe-
cial properties, is determined by the totality of its biophors.
These biophors are not, however, such simple structures as
the atoms of the chemist ; indeed, they are to be looked on as
super-molecules, as complex groups of chemical molecules,
of determined character and arrangement. Moreover, as
these biophors are life-units, they possess the essential char-
acteristics of life, that is, the capacity to assimilate food,
to grow, and to reproduce themselves by division. The num-
ber of different biophors is almost inconceivably enormous ;
for it must equal the possibilities of variety in character
exhibited by, or capable of being exhibited by, all the cells
of the body. But as each biophor is made of many complex
molecules which may vary among themselves, and also vary
in their structural relation to each other inside the biophor,
it is not difficult, perhaps, to imagine the possible variety of
biophors to be equal to the possible variety of cell char-
acters. These biophors are/ conceived to be united into
fixed, indissoluble groups tailed determinants, each de-
terminant containing all the biophors necessary to deter-
mine the whole character of any one kind of cell. Like
the biophors the determinants can assimilate food, grow
and multiply by division. While in each specialised body-
cell there needs to be but a single determinant, namely,
one of the special kind conforming to the special kind
of cell, in the germ-cells there must be co'nceived to be
every kind of determinant which may be found in all
the body-cells taken together. But, fortunately, by virtue
of the determinants' capacity for multiplication it is
not necessary to assume that there exists in the germ a



OTHER THEORIES OF SPECIES-FORMING. 197

determinant for every cell that is to develop in the body, but
only one for every different kind of cell; all cells exactly
alike can be supplied with similar determinants by the multi-
plication of the proper kind. Now Weismann's theory of
germinal selection rests upon the assumption of a competi-
tion or "struggle" of the determinants in the germ-plasm
for food and hence for opportunity to grow, to be vigorous,
and to multiply. The germ-cells derive their food, as do
the other cells and tissues of the body, from the general
food streams circulating around and through the cells.
Weismann, recognising the absolute principle of slight varia-
tion everywhere in Nature, it is practically impossible to
conceive of identity, believes that the initially slightly
stronger or more capable determinants will be able to take
up larger supplies of food, even to the extent of lessening
the supply for neighbouring determinants, perhaps to the
degree of starvation. Indeed he suggests a reason for the
initial slight variations in vigour of the determinants in the
probability that the food will reach the various determinants
in slightly, purely fortuitously, variable quantity, so that
the first inequality in vigour of the determinants will depend
on the fortuitous variability of food supply, while there-
after the variability in the determinants thus produced will
enable the stronger ones to draw to themselves or take up
more food and thus accumulate determinately the initial
fortuitous inequality.

Thus when the germ-cell begins its development into
a new individual those kinds of cells, tissues, and organs
will be best developed whose determinants were most suc-
cessful in the struggle for food, while other parts of
the body may be made smaller or even may not appear
at all because of the starvation of the determinants re -
sponsible for the cells which should compose them. Also
these better-developed, larger, more vigorous determinants
of one generation will hand on to the germ-plasm of the



198 DARWINISM TO-DAY.

next generation strong and extra-vigorous daughter deter-
minants. For any determinant in the germ-plasm of a fer-
tilised egg-cell has not alone to furnish determinants which
shall control the development of body.-tissues and organs
of the individual which develops from this cell, but also to
furnish daughter determinants for the new germ-plasm of
this individual. This will result in a repetition of the
extra-development in the next generation of the same organs
as were strongly developed in the first generation, and the
under-development of the same organs as were weak or
wanting in the first generation. Which process continued
is simply determinate variation, that is, variation along
fixed lines without reference to personal selec-
tion - Now when this variation becomes so



indeterminate marked that it is of life-and-death advantage
or disadvantage in the life of the individual, it
will immediately become subject to the control of personal
natural selection, and under the influence of this dominant
factor in determining adaptation, either be further fostered
and fixed or be extinguished. If the increasing organ or
part due to germinal selection be one whose increase is
advantageous to the individuals possessing it, then natural
selection will preserve those individuals and the germinal
advantage of the determinants of this part will be steadily
increased, as the size and power of assimilation of the
determinants correspond to the size and vigour of the part.
By this theory Weismann believes that he has explained
away one of the most potent objections to natural selection,
viz., that it is necessary to assume, for the effective work of
selection, the timely . appearance of the proper variations
necessary for the continued advantageous modification of
a part. "Knowing this factor, we remove, it seems to me,"
writes Weismann/ "the patent contradiction of the assump-
tion that the general fitness of organisms or the adaptations
necessary to their existence, are produced by accidental



OTHER THEORIES OF SPECIES-FORMING. 199

variations a contradiction which formed a serious stum-
bling-block to the theory of selection. Though still assum-
ing that primary variations are 'accidental/ I yet hope to
have demonstrated that an interior mechanism exists which
compels them to go on increasing in a definite direction, the
moment selection intervenes. Definitely directed variation
exists, but not predestined variation running on independ-
ently of the life conditions of the organism as Nageli, to
mention the position that the most extreme advocate of
this doctrine has assumed : on the contrary, the variation is
such as is elicited and controlled by those conditions them-
selves, though indirectly."

Obviously Weismann in his theory of germinal selection
has preserved the actuality of a struggle and a selection, but
with a "rehabilitation" of natural selection in the real Dar-
winian meaning and only fair application of the phrase the
new theory has nothing to do. It is, much more, a distinct
admission of the inadequacy of natural selection to do what
has long been claimed for it. It is the first serious attempt
at a causo-mechanical explanation of a theory of ortho-
genesis, that is, variation along determined lines.

As to our acceptance or non-acceptance of such a theory



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 18 of 38)