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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 33 of 38)
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shows the mutations that arose between 1887 and 1899 from
these plants. The seeds were selected in each case from
self-fertilised plants of the lamarckiana form, so that the
new plants appearing in each horizontal line are the
descendants in each generation of lamarckiana parents. It
will be observed that the species, O. oblongata, appeared
again and again in considerable numbers, and the same is



OTHER THEORIES OF SPECIES-FORMING. 347

true for several of the other forms also. Only the two
species, O, gigas and O. scintillans, appeared very rarely.

"Thus de Vries had, in his seven generations, about fifty
thousand plants, and about eight hundred of these were
mutations. When the flowers of the new forms were arti-
ficially fertilised with pollen from the flowers on the same
plant.'* or of the same kind of plant, they gave rise to forms
like themselves, thus showing that they are true elementary
species.* It is also a point of some interest to observe that
all these forms differed from each other in a large number
of particulars.

"Only one form, O. scintillans, that appeared eight times,
is not constant as are the other species. When self-
fertilised its seeds produce always three other forms, O.
scintillans, O. oblongata, and O. lamarckiana. It differs in
this respect from all the other elementary species, which
mutate not more than once in ten thousand individuals.

"From the seeds of one of the new forms, O. Icrvifolia, col-
lected in the field, plants were reared, some of which were
O. lamarckiana and others O. l&vifolia. They were allowed
to grow together, and their descendants gave rise to the
same forms found in the lamarckiana family, described
above, namely, O. lata, elliptica, nannella, rubrinervis, and
also two new species, O. spatnlata and leptocarpa.

"In the lata family only female flowers are produced, and,
therefore, in order to obtain seeds they were fertilised with
pollen from other species. Here also appeared some of the
new species already mentioned, namely, albida, nannella,
lata, oblongata, rubrinervis, and also two new species, ellip-
tica and subovata.

"De Vries also watched the field from which the original
forms were obtained, and found there many of the new
species that appeared under cultivation. These were found,

* O. lata is always female, and cannot, therefore, be self- fertilised.
When crossed with O. lamarckiana there is produced fifteen to twenty
per cent, of pure lata individuals.



348 DARWINISM TO-DAY.

however, only as weak young plants that rarely flowered.
Five of the new forms were seen either in the Hilversum
field, or else raised from seeds that had been collected there.
These facts show that the new species are not due to culti-
vation, and that they arise year after year from the seeds
of the parent form, O. lamarckiana."

Since the publication of de Vries's theory and the data
and considerations on which it is based (these considera-
tions including an unusually keen and effective
criticism of the Darwinian factors of species-
ward the muta- forming) a great deal of discussion of the
60171 theory has been indulged in. On the whole
the theory has been warmly welcomed as the most promis-
ing way yet presented " out of the difficulties into which
biologists had fallen in their attempts to explain satisfactorily
the phenomena of the origin of species through Darwinian
selection. And especially has been welcomed the fruitful idea
of unit species characters, and of the indivisibility and the
distinctness of such characters in inheritance. But with all
the interest aroused by de Vries's presentation of his theory,
and with all the eager scrutiny of species and records of
species-appearing an output of new evidence amazingly
small (when one stops to consider the publicity gained for
the theory itself and its obvious need of more confirmatory
data of observation and experiment) has resulted. Even
though the answer may be that experiment takes time, the
lack of new observational evidence of the occurrence of
mutations," and of the origin of new species through muta-
tions in nature, is significant. It is my belief that a reaction
against the curiously swift and widespread partial to com-
plete acceptance of the mutation theory as the sufficient "way
out" of our troubles to explain the origin of new species will
soon occur. ( See notes 24, 25, and 26, the appendix of this
chapter, for references to certain recent criticisms of the
mutation theory.)



OTHER THEORIES OF SPECIES-FORMING. 349

In closing this confessedly inadequate consideration of
the important work and theorising of de Vries we should
not fail to note that the mutations theory is
m stron g contrast to any theory of species-



trastedwith forming based on Lamarckian principles in that

Lamarckism.

the newly appearing differences in organisms
leading- to the establishment of new species are purely con-
genital : that is, the mutations arise in one or both of the
sex cells and only later appear in the adult organism. There
is no question of the transference to the germ-cells of
changes induced in the soma by use or disuse or functional
stimulus in such a way as to result in the photographic
reappearance of these changes in the offspring. Mutations
are true congenital or blastogenic variations. "The muta-
tion theory," well says Conklin, 27 "is a theory of the evolu-
tion of organisms through the evolution of their germ-cells."

The mutations theory is also in sharp contrast to the
theory of species-forming by geographical isolation (see
chapter ix). According to de Vries many dis-
theory contrasted tinct species (de Vriesian elementary species)
with the isola- can an( j (j o exist side by side in the same range.
In fact they "are found to be heaped up in the
centre of their area of distribution, but are more scattered
at the periphery." 2 Now according to Wagner, Gulick,
and Jordan two closely allied species, i. e., stock and off-
shoot, are found practically never to inhabit the same range,
except in those cases where a migration of one type into
the territory of the other has taken place after the differ-
entiation has been effected (by previous segregation).

It would carry us into too extended a discussion to at-
tempt to sum up here the pertinent criticism that has been
directed against the mutations theory. As already indicated,
there is plenty of it and of distinctly non-negligible char-
acter. But just now it seems to me sufficient simply to call
attention to the extreme meagreness in quantity of the real



35 o DARWINISM TO-DAY.

scientific evidence for the theory as a theory capable of ex-
plaining species-forming as a whole. There is probably no
gainsaying the actuality of the occurrence of certain muta-
tions (in de Vries's .sense) nor of their establishment of
certain apparently fixed new organic types (de Vries's
elementary species of (Enothera). But this is very far
from accepting the mutations theory as a sufficient causal
explanation of the origin of the hundreds of thousands of
species of animals and plants that are now or were formerly
existent.

As for the help that the establishment of the mutations
theory would give those biologists who reject the natural
Mor MI'S sum- selection theory of species-forming, Morgan "
ationofthe writes as follows, summing up the advantages
of the theory:

"i. Since the mutations appear fully formed
from the beginning, there is no difficulty in accounting for
the incipient stages in the development of an organ, and
since the organ may persist, even when it has no value to
the race, it may become further developed by later muta-
tions and may come to have finally an important relation to
the life of the individual.

"2. The new mutations may appear in large numbers, and
of the different kinds those will persist that can get a foot-
hold. On account of the large number of times that the
same mutations appear, the danger of becoming swamped
through crossing with the original form will be lessened
in proportion to the number of new individuals that arise.
"3. If the time of reaching maturity in the new form is
different from that in the parent forms, then the new species
will be kept from crossing with the parent form, and since
this new character will be present from the beginning, the
new form will have much better chances of surviving than
if a difference in time of reaching maturity had to be gradu-
ally acquired.



OTHER THEORIES OF SPECIES-FORMING. 351

"4. The new species that appear may be in some cases
already adapted to live in a different environment from that
occupied by the parent form; and if so, it will be isolated
from the beginning, which will be an advantage in avoiding
the bad effects of intercrossing.

"5. It is well known that the differences between related
species consist largely in differences of unimportant organs,
and this is in harmony with the mutation theory, but one
of the real difficulties of the selection theory.

"6. Useless or even slightly injurious characters may
appear as mutations, and if they do not seriously affect the
perpetuation of the race, they may persist."

Finally, the attention of students especially may be called
to Bateson's interesting suggestion that mutations may be
Bateson's sug- s ^ m P^y pure Mendelian recessives appearing
gestion that mu- after a crossing. It would take us too far
Mendelian re- afield to attempt to explain here to readers
cessives. unacquainted with the Mendelian principles

of inheritance just how Bateson's suggestion has a certain
plausibility. It must suffice to say that Mendel, and after
him a considerable number of present-day students of
heredity, have shown that after a crossing between two*
individuals sharply contrasting in regard to some particular
character, as colour of hair, all the offspring of the first
generation may agree in showing but one of the two parental
colours (the dominant), but that if these first generation
offspring are bred to each other, or to similarly produced in-
dividuals, the members of the second generation will split
up as regards the character in question, some showing one
of the grand-parental hair colours, and the rest showing the
other one. Now breeding likes together, it would be shown
in third generation groups that one of these colours, and,
namely, that one called the recessive, which did not appear
at all in the first generation, will always henceforth breed
true while the other colour may or may not breed true (de-



352 DARWINISM TO-DAY.

pending on whether in making the matings pure dominants
or cross-bred dominants happen to be used). Thus the
sudden appearance in the second generation of the latent or
recessive characteristic, and its breeding true, are occur-
rences which might readily be interpreted as the appearance
of a mutation or true-breeding sport by an observer unac-
quainted with the ancestry of the individuals under his eye.

Alternative Theories to Explain Secondary Sexual Char-
acters. Before closing this discussion of theories which
have been proposed as substitutes for the Darwinian selec-
tion theories to explain the actual conditions in the organic
world as we see it to-day, and as we know it to have been
in past ages, we should mention, at least, the few attempts
to formulate a substitute explanation for the existence of
secondary sexual characters. The discrediting of the sexual
selection theory as such an explanation is certainly nearly
complete. But it is interesting to note how lame and uncon-
vincing are the proposed substitute explanations.

The first, and most appealing one, is the explanation that

the extra plumes, wattles, horns, the unusual display of

bright colours, etc., of the males are simply the

Extra growth manifestations of an extra growth-force or

the result of

extra vigour. vigour exhibited by the male in the breeding
season. The female also may be endowed with
extra growth-vigour at this time, but it goes, in her case, to
the formation of ova, to the storing up of food in or around
the egg cells. The songs, the dances, the violent play and
antics of the males common to many species of birds, insects,
spiders, etc., are also attributed to this special or sexual
vigour.

Now while such secondary sexual characters as colour,
plumes, wattles, etc., might perhaps well enough seem to
be the outcome of an extra growth- vigour, what about such
special male characters as the stridulating organs of male
katydids and crickets, and other similar complex, highly



OTHER THEORIES OF SPECIES-FORMING. 353

perfected, adaptive structures? A male cricket has the
veins at the base of one wing-cover curiously and com-
plexly modified in course and in superficial structure, while
the veins of the other wing-cover are also modified in a way
differing from but exactly correlated with the venation of
the first wing, the whole specialisation resulting in a com-
bination of file, scraper, and vibrating membrane to form the
effective musical instrument of the insect. Can such an
adaptive structural modification be conceived to be a sudden
bursting forth or result of superabundant growth-force?
And many of the secondary sexual characters are of this
class of complex adaptive specialisations. The growth-
force explanation can, at best, explain but few of the various
categories of sexual dimorphism. Some explanation more
directive in its character is needed for these others.

Even more restricted in its application, and less con-
vincing in the assumptions at its very base, is the curious
replacement theory of Emery. 80 This investi-
gator believes that sexual selection can explain



secondary sexual but few if any cases of sexual dimorphism, and

characters i *

would explain these other cases largely by the
sudden appearance (mutation or sport) of a second form
of male or female, the persistence for a while of the two
forms side by side, as now exemplified by numerous dimor-
phic or polymorphic (or di- or polychromatic) species, and
then the gradual or sudden dying out (killing out by selec-
tion?) of the older original form (the one resembling the
other sex), thus leaving the once dimorphic sex represented
only by the newer aberrant form. While such an explana-
tion may possibly explain a few cases of extreme sexual
dimorphism or dichromatism, it certainly will not do for
the many cases of secondary sexual difference constituted
by the existence in one sex of some one or few particular
adaptive specialisations for music-making, scent-producing,
or weapon-forming, not possessed by the other sex.



354 DARWINISM TO-DAY.

Cunningham" (and also at about the same time Wigles-
worth) in 1898 suggested, on a neo-Lamarckian basis, that
secondary sexual characters were due to the
stimulation of parts through use or external
secondary senal violence or irritation. Cunningham would ex-
plain all adaptations as derived from variations
actually induced by responses or reactions to the environ-
ment. His theory of the origin of secondary sexual char-
acters would simply be the explanation of the adaptive dif-
ferences between two individuals of a species on the same
basis as the explanation of the adaptive differences between
individuals of different species. His argument is summed
up as follows : "Selection assumes the occurrence of varia-
tions ; the variations must either be similarly indefinite and
promiscuous in all cases, or they must be different in differ-
ent cases that is, in different species, different sexes, dif-
ferent stages of life. If they are different in different cases,
then selection is a very unimportant matter, for the chief
questions are evidently what are the differences and what
made them differ. To deny that the variations have always
been different in different cases is to deny the most evident
facts ; such denial might be possible when we consider only
the difference between species, but it is impossible when
we study the differences between the sexes in the same
species and between different stages in the same individual.
In all cases the variations correspond to differences in habits
and mode of life, and in many cases are of the same kind
as the changes known to be produced in the individual by
special stimulation or special activity of organs ; this is true
of many and probably of all cases of adaptation. The gen-
eral conclusion is that adaptation is not produced indirectly
by the selection from indefinite variations, but directly by the
influence of stimulation in modifying the growth of the
parts or organs of the body."

Wallace" has suggested that the differences in color-



OTHER THEORIES OF SPECIES-FORMING. 355

ation between males and females are due largely to the
necessity of the better protection of the young
ro W estion'* producing and (in the case of birds and mam-
mals) young protecting and caring for female,
and hence the acquirement on her part of a dull incon-
spicuous protective colour-pattern. Wallace's large ac-
quaintanceship with birds and butterflies enables him to
illustrate his theory by many apparently confirmatory ex-
amples, but as soon as one stops to consider the matter
thoughtfully the impossibility of the general or even wide
application of this explanation of secondary sexual char-
acters is at once apparent. It is necessarily limited to one
single category of sexual differences.

Barrett-Hamilton 33 has noted that both sexes of the sal-
mon (Onchorhynchus) become markedly discoloured during
the spawning season. The discoloration is accompanied by
overgrowth or hypertrophy, especially of the jaws. "I can-
not believe," he says, "that this is of an aesthetic nature, since
these phenomena terminate in the death of the fish. They
seem to be, in fact, merely the outward symptoms of what,
as I have persuaded myself from personal observation in
Kamschatka, is a pathological condition accompanying, and
perhaps resulting from, the growth of the ova and milt.
I regard the whole metamorphosis as a purely excretory
phenomenon resulting from the upsetting of the metab-
olism due to the concentration of the whole vital force
on the effort to produce the greatest possible amount of
spawn.

"May not such a state of things be invoked to explain the
nuptial changes of our own salmon so strangely assumed
before and lost after the breeding-season ? Is it not possible
that in the phenomena displayed by the spawning Oncho-
rhynchus we may have a clue to the origin of the hitherto
inexplicable temporary and permanent sexual characters
of the vertebrates and even of some invertebrates, of which



356 DARWINISM TO-DAY.

it may be that the origin has been primarily excretory and
only secondarily protective or aesthetic ?"

The plain truth is that the satisfactory, all-explaining ex-
planation of secondary sexual characters and sexual dimor-
phism as a whole is yet to be formulated.

APPENDIX.

1 At some time between 1855 and 1865, Gregor Johann Mendel,
an Augustinian monk in the small Austrian village of Brunn, car-
Mendel and ried on pedigree cultures of peas and some other
his work. plants in the gardens of his cloister. From this work

he derived data that he read, together with his interpretation of
their significance, before meetings of the Natural History Society
of Brunn, and which, in the same year of their reading, 1865, were
published under the title "Experiments in Plant-hybridisation," in
the Abhandlungen (Vol. IV.) of the society. Mendel was the son
of a peasant and had been educated in Augustinian foundations and
ordained priest. For two or three years he studied physics and
natural science in Vienna, and refers to himself as a student of
Kollar. He became Abbot of his cloister, and was for a time
president of the Brunn Natural History Society. Such are the
essential details of the education and situation of the man whose
name will undoubtedly live forever in the annals of biological
science. For the observations, experiments, and conclusions of
Mendel on inheritance have taken their place already as matters of
fundamental importance in the study of heredity. It would take
us too far afield even to outline Mendel's work and derived "princi-
ples of heredity," but the interested reader can find an admirable
exposition and discussion of them (together with translations of
Mendel's own papers) in Bateson's "Mendel's Principles of Hered-
ity," 1902.

For an excellent exposition of Mendel's work and other similar
work by botanists, see Lotsy, J. P., "Vorlesungen uber Descendenz-
theorien," Vol. I, chap. viii. 1906.

Cuenot, in L'Annee Biologique, Vol. VII, for 1902, pp. 58-77,
gives an excellent review of the work of Mendel, de Vries, Cor-
rens. and Tschermak; and a bibliography, relating to the so-called
Mendelian laws of the principles of heredity.

Bateson, in "Progressus rei Botannicae," Vol. I, pp. 368-468, 1907,
gives a complete abstract of the nature of the work and its results
which has been done on the Mendelian problem from the time of



OTHER THEORIES OF SPECIES-FORMING. 357

Mendel to the present. The bibliography in connection with this
paper is practically complete up to the date of its making.

2 Correns, C. G., "Uber Levkoyen-Bastarde, zur Kenntniss der
Grenzen der Mendel'schen Regeln," Botan. Centralbl., LXXXIV,
Beferencesto P- 97. 190; "Uber Bastarde zwischen Rassen von
recent work on Zea Mays," Bcr. Deut. Bot. Ges., XIX, 211 (1901);
Mendelism. "Bastarde zwischen Maisrassen, Bibliotheca Bota-

nica/'-'Heft 53, 1901; "Uber Bastardirungs-Versuche mit Mirabilis-
Sippen," Ber. Deut. Bot. Ges., XX, 594-608, 1903.

' T. E. Tschermak, "Uber kiinstliche Kreuzung bei Pisum sati-
vum," Zeitschr. f. d. Landivirthsch. Versuchswesen, III, 465-555,
1900 ; "Weitere Beitrage uber Verschiedenswerthigkeit der
Merkmale bei Kreuzung von Erbsen und Bohnen," ibid. IV, 641 ff.,
1901 ; "Uber Zuchtung neuer Getreiderassen mittelst kiinstlicher
Kreuzung," ibid. IV, 1902. "Die Theorie der Kryptomerie und des
Kryptohybridismus," Beihefte z. Bot. Centralbl., XVI, 25 pp., 1903;
"Weitere Kreuzungsstudien an Erbsen," Zeitschrift f. d. Landwirth-
Versuchswesen in Ocsterr., 106 pp., 1904.

4 See Darwin, "Animals and Plants Under Domestication," Vol.
I, chap, iii, p. 104. "In some few instances new breeds [of sheep]
Darwin on have suddenly originated ; thus in 1791 a ram-lamb was
race origin from born in Massachusetts, having short crooked legs and
sports. a i on g back, like a turnspit dog. From this one lamb

the otter, or ancon, a semi-monstrous breed, was raised; as these
sheep could not leap over the fences it was thought that they would
be valuable ; but they have been supplanted by merinos, and thus
exterminated.' The sheep are remarkable from transmitting their
character so truly that Colonel Humphreys never heard of 'but one
questionable case' of an ancon ram and ewe not producing ancon
offspring. When they are crossed with other breeds the offspring,
with rare exceptions, instead of being intermediate in character,
perfectly resemble either parent ; even one of twins has resembled
one parent and the second the other. Lastly, 'the ancons have been
observed to keep together, separating themselves from the rest of
the flock when put into enclosures with other sheep.'

"A more interesting case has been recorded in the Report of
the Juries for the Great Exhibition (1851), namely, the produc-
tion of a merino ram-lamb on the Mauchamp farm, in 1828, which
was remarkable for its long, smooth, straight, and silky wool. By
the year 1833 M. Graux had raised rams enough to serve his whole
flock, and after a few more years he was able to sell stock of his
new breed. So peculiar and valuable is the wool, that it sells at
25 per cent, above the best merino wool : even the fleeces of half-
bred animals are valuable, and are known in France as the



358 DARWINISM TO-DAY.

'Mauchamp-merino.' It is interesting, as showing how generally
any marked deviation of structure is accompanied by other devia-
tions, that the first ram and his immediate offspring were of small
size, with large heads, long necks, narrow chests, and long flanks,
but these blemishes were removed by judicious crosses and selec-
tion. The long smooth wool was also correlated with smooth horns ;
and as horns and hair are homologous structures, we can under-
stand the meaning of this correlation. If the Mauchamp and ancon
breeds had originated a century or two ago, we should have no
record of their birth ; and many a naturalist would no doubt have



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 33 of 38)