On the Genesis of Species

S >> St. George Mivart >> On the Genesis of Species

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In such creatures we see that, from time to time, one of the segments of
the body gradually becomes modified till it assumes the condition of a
head, and this remarkable phenomenon is repeated again and again, the body
of the worm thus multiplying serially into new individuals which
successively detach themselves from the older portion. The development of
such a mode of reproduction by "Natural Selection" seems not less
inexplicable than does its continued performance through the aid of {212}
"pangenesis." For how can gemmules attach themselves to others to which
they do not normally or generally succeed? Scarcely less difficult to
understand is the process of the stomach-carrying-off mode of metamorphosis
before spoken of as existing in the Echinoderms. Next, as to certain patent
and notorious facts: On the hypothesis of pangenesis, no creature can
develop an organ unless it possesses the component gemmules which serve for
its formation. No creature can possess such gemmules unless it inherits
them from its parents, grandparents, or its less remote ancestors. Now, the
Jews are remarkably scrupulous as to marriage, and rarely contract such a
union with individuals not of their own race. This practice has gone on for
thousands of years, and similarly also for thousands of years the rite of
circumcision has been unfailingly and carefully performed. If then the
hypothesis of pangenesis is well founded, that rite ought to be now
absolutely or nearly superfluous from the necessarily continuous absence of
certain gemmules through so many centuries and so many generations. Yet it
is not at all so, and this fact seems to amount almost to an experimental
demonstration that the hypothesis of pangenesis is an insufficient
explanation of individual evolution.

Two exceedingly good criticisms of Mr. Darwin's hypothesis have appeared.
One of these is by Mr. G. H. Lewes,[221] the other by Professor Delpino of
Florence.[222] The latter gentleman gives a report of an observation made
by him upon a certain plant, which observation adds force to what has just
been said about the Jewish race. He says:[223] "If we examine and compare
the numerous species of the genus _Salvia_, commencing with _Salvia
officinalis_, which may pass as the main state of the genus, and {213}
concluding with _Salvia verticillata_, which may be taken as the most
highly developed form, and as the most distant from the type, we observe a
singular phenomenon. The lower cell of each of the two fertile anthers,
which is much reduced and different from the superior even in _Salvia
officinalis_, is transmuted in other _salviae_ into an organ (nectarotheca)
having a very different form and function, and finally disappears entirely
in _Salvia verticillata_.

"Now, on one occasion, in a flower belonging to an individual of _Salvia
verticillata_, and only on the left stamen, I observed a perfectly
developed and pollinigerous lower cell, perfectly homologous with that
which is normally developed in _Salvia officinalis_. This case of atavism
is truly singular. According to the theory of Pangenesis, it is necessary
to assume that all the gemmules of this anomalous formation, and therefore
the mother-gemmule of the cell, and the daughter-gemmules of the special
epidermic tissue, and of the very singular subjacent tissue of the
endothecium, have been perpetuated, and transmitted from parent to
offspring in a dormant state, and through a number of generations, such as
startles the imagination, and leads it to refuse its consent to the theory
of Pangenesis, however seductive it may be." This seems a strong
confirmation of what has been here advanced.

The main objection raised against Mr. Darwin's hypothesis is that it
(Pangenesis) requires so many subordinate hypotheses for its support, and
that some of these are not tenable.

Professor Delpino considers[224] that as many as eight of these subordinate
hypotheses are required, namely, that--

"1. The emission of the gemmules takes place, or may take place in all
states of the cell.

"2. The quantity of gemmules emitted from every cell is very great.

"3. The minuteness of the gemmules is extreme.

{214}
"4. The gemmules possess two sorts of affinity, one of which might be
called _propagative_, and the other _germinative_ affinity.

"5. By means of the propagative affinity all the gemmules emitted by all
the cells of the individual flow together and become condensed in the cells
which compose the sexual organs, whether male or female (embryonal vesicle,
cells of the embryo, pollen grains, fovilla, antherozoids, spermatozoids),
and likewise flow together and become condensed in the cells which
constitute the organs of a sexual or agamic reproduction (buds, spores,
bulbilli, portions of the body separated by scission, &c.).

"6. By means of the germinative affinity, every gemmule (except in cases of
anomalies or monstrosities) can be developed only in cells homologous with
the mother-cells of the cell from which they originated. In other words,
the gemmules from any cell can only be developed in unison with the cell
preceding it in due order of succession, and whilst in a nascent state.

"7. Of each kind of gernmule a great number perishes; a great number
remains in a dormant state through many generations in the bodies of
descendants; the remainder germinate and reproduce the mother-cell.

"8. Every gemmule may multiply itself by a process of scission into any
number of equivalent gemmules."

Mr. Darwin has published a short notice in reply to Professor Delpino, in
_Scientific Opinion_ of October 20, 1869, p. 426. In this reply he admits
the justice of Professor Delpino's attack, but objects to the alleged
necessity of the first subordinate hypothesis, namely, that the emission of
gemmules takes place in all states of the cell. But if this is not the
case, then a great part of the utility and distinction of pangenesis is
destroyed, or as Mr. Lewes justly says,[225] "If gemmules produce whole
cells, we have the very power which was pronounced mysterious in larger
organisms."

{215}
Mr. Darwin also does not see the force of the objection to the power of
self-division which must be asserted of the gemmules themselves if
Pangenesis be true. The objection, however, appears to many to be
formidable. To admit the power of spontaneous division and multiplication
in such rudimentary structures, seems a complete contradiction. The
gemmules, by the hypothesis of Pangenesis, are the ultimate organized
components of the body, the absolute organic atoms of which each body is
composed; how then _can_ they be divisible? Any part of a gemmule would be
an impossible (because a _less_ than possible) quantity. If it is divisible
into still smaller organic wholes, as a germ-cell is, it must be made up as
the germ-cell is, of subordinate component atoms, which are then the _true_
gemmules. This process may be repeated _ad infinitum_, unless we get to
true organic atoms, the true gemmules, whatever they may be, and they
necessarily will be incapable of any process of spontaneous fission. It is
remarkable that Mr. Darwin brings forward in support of gemmule fission,
the observation that "Thuret has seen the zoospore of an alga divide
itself, and both halves germinate." Yet on the hypothesis of Pangenesis,
the zoospore of an alga must contain gemmules from all the cells of the
parent algae, and from all the parts of all their less remote ancestors in
all their stages of existence. What wonder then that such an excessively
complex body should divide and multiply; and what parity is there between
such a body and a gemmule? A steam-engine and a steel-filing might equally
well be compared together.

Professor Delpino makes a further objection which, however, will only be of
weight in the eyes of Vitalists. He says,[226] Pangenesis is not to be
received because "it leads directly to the negation of a specific vital
principle, co-ordinating and regulating all the movements, acts, and
functions of the individuals in which it is incarnated. For Pangenesis of
the individual is a term without meaning. If, in contemplating an {216}
animal of high organization, we regard it purely as an aggregation of
developed gemmules, although these gemmules have been evolved successively
one after the other, and one within the other, notwithstanding they elude
the conception of the _real and true individual_, these problematical and
invisible gemmules must be regarded as so many individuals. Now, that real,
true, living individuals exist in nature, is a truth which is persistently
attested to us by our consciousness. But how, then, can we explain that a
great quantity of dissimilar elements, like the atoms of matter, can unite
to form those perfect unities which we call individuals, if we do not
suppose the existence of a specific principle, proper to the individual but
foreign to the component atoms, which aggregates these said atoms, groups
them into molecules, and then moulds the molecules into cells, the cells
into tissues, the tissues into organs, and the organs into apparatus?"

"But, it may be urged in opposition by the Pangenesists, your vital
principle is an unknown and irresolute _x_. This is true; but, on the other
hand, let us see whether Pangenesis produces a clearer formula, and one
free from unknown elements. The existence of the gemmules is a first
unknown element; the propagative affinity of the gemmules is a second;
their germinative affinity is a third; their multiplication by fission is a
fourth--and what an unknown element!"

"Thus, in Pangenesis, everything proceeds by force of unknown elements, and
we may ask whether it is more logical to prefer a system which assumes a
multitude of unknown elements to a system which assumes only a single one?"

Mr. Darwin appears, by "Natural Selection," to destroy the reality of
species, and by Pangenesis that of the individual. Mr. Lewes observes[227]
of the individual that "This whole is only a subjective conception which
summarizes the parts, and that in point of fact it is the parts which {217}
are reproduced." But the parts are also, from the same point of view,
merely subjective until we come to the absolute organic atoms. These atoms,
on the other hand, are utterly invisible, intangible; indeed, in the words
of Mr. Darwin, inconceivable. Thus, then, it results from the theories in
question, that the organic world is reduced to utter unreality as regards
all that can be perceived by the senses or distinctly imagined by the mind;
while the only reality consists of the invisible, the insensible, the
inconceivable; in other words, nothing is known that really is, and only
the nonexistent can be known. A somewhat paradoxical outcome of the
speculations of those who profess to rely exclusively on the testimony of
sense. "_Les extremes se touchent_," and extreme sensationalism shakes
hands with the "das seyn ist das nichts" of Hegel.

Altogether the hypothesis of Pangenesis seems to be little, if at all,
superior to anterior hypotheses of a more or less similar nature.

Apart from the atoms of Democritus, and apart also from the speculations of
mediaeval writers, the molecules of Bonnet and of Buffon almost anticipated
the hypothesis of Pangenesis. According to the last-named author,[228]
organic particles from every part of the body assemble in the sexual
secretions, and by their union build up the embryo, each particle taking
its due place, and occupying in the offspring a similar position to that
which it occupied in the parents. In 1849 Professor Owen, in his treatise
on "Parthenogenesis," put forward another conception. According to this,
the cells resulting from the subdivision of the germ-cell preserve their
developmental force, unless employed in building up definite organic
structures. In certain creatures, and in certain parts of other creatures,
germ-cells unused are stored up, and by their agency lost limbs and {218}
other mutilations are repaired. Such unused products of the germ-cell are
also supposed to become located in the generative products.

According to Mr. Herbert Spencer, in his "Principles of Biology," each
living organism consists of certain so-called "physiological units." Each
of these units has an innate power and capacity, by which it tends to build
up and reproduce the entire organism of which it forms a part, unless in
the meantime its force is exhausted by its taking part in the production of
some distinct and definite tissue--a condition somewhat similar to that
conceived by Professor Owen.

Now, at first sight, Mr. Darwin's atomic theory appears to be more simple
than any of the others. It has been objected that while Mr. Spencer's
theory requires the assumption of an innate power and tendency in each
physiological unit, Mr. Darwin's, on the other hand, requires nothing of
the kind, but explains the evolution of each individual by purely
mechanical conceptions. In fact, however, it is not so. Each gemmule,
according to Mr. Darwin, is really the seat of powers, elective affinities,
and special tendencies as marked and mysterious as those possessed by the
physiological unit of Mr. Spencer, with the single exception that the
former has no tendency to build up the whole living, complex organism of
which it forms a part. Some may think this an important distinction, but it
can hardly be so, for Mr. Darwin considers that his gemmule has the innate
power and tendency to build up and transform itself into the whole living,
complex cell of which it forms a part; and the one tendency is, in
principle, fully as difficult to understand, fully as mysterious, as is the
other. The difference is but one of degree, not of kind. Moreover, the one
mystery in the case of the "physiological unit" explains all, while with
regard to the gemmule, as we have seen, it has to be supplemented by other
powers and tendencies, each distinct, and each in itself inexplicable and
profoundly mysterious. [Page 219]

That there should be physiological units possessed of the power attributed
to them, harmonizes with what has recently been put forward by Dr. H.
Charlton Bastian; who maintains that under fit conditions the simplest
organisms develop themselves into relatively large and complex ones. This
is not supposed by him to be due to any inheritance of ancestral gemmules,
but to direct growth and transformation of the most minute and the simplest
organisms, which themselves, by all reason and analogy, owe their existence
to immediate transformation from the inorganic world.

Thus, then, there are grave difficulties in the way of the reception of the
hypothesis of Pangenesis, which moreover, if established, would leave the
evolution of individual organisms, when thoroughly analysed, little if at
all less mysterious or really explicable than it is at present.

As was said at the beginning of this chapter, "Pangenesis" and "Natural
Selection" are quite separable and distinct hypotheses. The fall of one of
these by no means necessarily includes that of the other. Nevertheless, Mr.
Darwin has associated them closely together, and, therefore, the refutation
of Pangenesis may render it advisable for those who have hitherto accepted
"Natural Selection" to reconsider that theory. [Page 220]

* * * * *

CHAPTER XI.

SPECIFIC GENESIS.

Review of the statements and arguments of preceding
chapters.--Cumulative argument against predominant action of "Natural
Selection."--Whether anything positive as well as negative can be
enunciated.--Constancy of laws of nature does not necessarily imply
constancy of specific evolution.--Possible exceptional stability of
existing epoch.--Probability that an internal cause of change
exists.--Innate powers must be conceived as existing somewhere or
other.--Symbolism of molecular action under vibrating
impulses.--Professor Owen's statement.--Statement of the Author's
view.--It avoids the difficulties which oppose "Natural Selection."--It
harmonizes apparently conflicting conceptions.--Summary and conclusion.

Having now severally reviewed the principal biological facts which bear
upon specific manifestation, it remains to sum up the results, and to
endeavour to ascertain what, if anything, can be said _positively_, as well
as negatively, on this deeply interesting question.

In the preceding chapters it has been contended, in the first place, that
no mere survival of the fittest accidental and minute variations can
account for the incipient stages of useful structures, such as, _e.g._, the
heads of flat-fishes, the baleen of whales, vertebrate limbs, the laryngeal
structures of the newborn kangaroo, the pedicellariae of Echinoderms, or for
many of the facts of mimicry, and especially those last touches of mimetic
perfection, where an insect not only mimics a leaf, but one worm-eaten and
attacked by fungi. [Page 221]

Also, that structures like the hood of the cobra and the rattle of the
rattlesnake seem to require another explanation.

Again, it has been contended that instances of colour, as in some apes; of
beauty, as in some shell-fish; and of utility, as in many orchids, are
examples of conditions which are quite beyond the power of Natural
Selection to originate and develop.

Next, the peculiar mode of origin of the eye (by the simultaneous and
concurrent modification of distinct parts), with the wonderful refinement
of the human ear and voice, have been insisted on; as also, that the
importance of all these facts is intensified through the necessity
(admitted by Mr. Darwin) that many individuals should be similarly and
simultaneously modified in order that slightly favourable variations may
hold their own in the struggle for life, against the overwhelming force and
influence of mere number.

Again, we have considered, in the third chapter, the great improbability
that from minute variations in all directions alone and unaided, save by
the survival of the fittest, closely similar structures should
independently arise; though, on a non-Darwinian evolutionary hypothesis,
their development might be expected _a priori_. We have seen, however, that
there are many instances of wonderfully close similarity which are not due
to genetic affinity; the most notable instance, perhaps, being that brought
forward by Mr. Murphy, namely, the appearance of the same eye-structure in
the vertebrate and molluscous sub-kingdoms. A curious resemblance, though
less in degree, has also been seen to exist between the auditory organs of
fishes and of Cephalopods. Remarkable similarities between certain
placental and implacental mammals, between the bird's-head processes of
Polyzoa and the pedicellariae of Echinoderms, between Ichthyosauria and
Cetacea, with very many other similar coincidences, have also been pointed
out.

Evidence has also been brought forward to show that similarity is sometimes
directly induced by very obscure conditions, at present quite {222}
inexplicable, _e.g._ by causes immediately connected with geographical
distribution; as in the loss of the tail in certain forms of Lepidoptera
and in simultaneous modifications of colour in others, and in the direct
modification of young English oysters, when transported to the shore of the
Mediterranean.

Again, it has been asserted that certain groups of organic forms seem to
have an innate tendency to remarkable developments of some particular kind,
as beauty and singularity of plumage in the group of birds of paradise.

It has also been contended that there is something to be said in favour of
sudden, as opposed to exceedingly minute and gradual, modifications, even
if the latter are not fortuitous. Cases were brought forward, in Chapter
IV., such as the bivalve just mentioned, twenty-seven kinds of American
trees simultaneously and similarly modified, also the independent
production of pony breeds, and the case of the English greyhounds in
Mexico, the offspring of which produced directly acclimated progeny.
Besides these, the case of the Normandy pigs, of _Datura tatula_, and also
of the black-shouldered peacock, have been spoken of. The teeth of the
labyrinthodon, the hand of the potto, the whalebone of whales, the wings of
birds, the climbing tendrils of some plants, &c. have also been adduced as
instances of structures, the origin and production of which are probably
due rather to considerable modifications than to minute increments.

It has also been shown that certain forms which were once supposed to be
especially transitional and intermediate (as, _e.g._, the aye-aye) are
really by no means so; while the general rule, that the progress of forms
has been "from the more general to the more special," has been shown to
present remarkable exceptions, as, _e.g._, Macrauchenia, the Glyptodon, and
the sabre-toothed tiger (Machairodus).

Next, as to specific stability, it has been seen that there may be a {223}
certain limit to normal variability, and that if changes take place they
may be expected _a priori_ to be marked and considerable ones, from the
facts of the inorganic world, and perhaps also of the lowest forms of the
organic world. It has also been seen that with regard to minute spontaneous
variations in races, there is a rapidly increasing difficulty in
intensifying them, in any one direction, by ever such careful breeding.
Moreover, it has appeared that different species show a tendency to
variability in special directions, and probably in different degrees, and
that at any rate Mr. Darwin himself concedes the existence of an internal
barrier to change when he credits the goose with "a singularly inflexible
organization;" also, that he admits the presence of an _internal_
proclivity to change when he speaks of "a whole organization seeming to
have become plastic, and tending to depart from the parental type."

We have seen also that a marked tendency to reversion does exist, inasmuch
as it sometimes takes place in a striking manner, as exemplified in the
white silk fowl in England, _in spite of_ careful selection in breeding.

Again, we have seen that a tendency exists in nature to eliminate hybrid
races, by whatever means that elimination is effected, while no similar
tendency bars the way to an indefinite blending of varieties. This has also
been enforced by statements as to the prepotency of certain pollen of
identical species, but of distinct races.

To all the preceding considerations have been added others derived from the
relations of species to past time. It has been contended that we have as
yet no evidence of minutely intermediate forms connecting uninterruptedly
together undoubtedly distinct species. That while even "horse ancestry"
fails to supply such a desideratum, in very strongly marked and exceptional
kinds (such as the Ichthyosauria, Chelonia, and Anoura), the absence of
links is very important and significant. For if every species, without{224}
exception, has arisen by minute modifications, it seems incredible that a
small percentage of such transitional forms should not have been preserved.
This, of course, is especially the case as regards the marine Ichthyosauria
and Plesiosauria, of which such numbers of remains have been discovered.

Sir William Thomson's great authority has been seen to oppose itself to
"Natural Selection," by limiting, on astronomical and physical grounds, the
duration of life on this planet to about one hundred million years. This
period, it has been contended, is not nearly enough on the one hand for the
evolution of all organic forms by the exclusive action of mere minute,
fortuitous variations; on the other hand, for the deposition of all the
strata which must have been deposited, if minute fortuitous variation was
the manner of successive specific manifestation.

Again, the geographical distribution of existing animals has been seen to
present difficulties which, though not themselves insurmountable, yet have
a certain weight when taken in conjunction with all the other objections.

The facts of homology, serial, bilateral and vertical, have also been
passed in review. Such facts, it has been contended, are not explicable
without admitting the action of what may most conveniently be spoken of as
an _internal_ power, the existence of which is supported by facts not only
of comparative anatomy but of teratology and pathology also. "Natural
Selection" also has been shown to be impotent to explain these phenomena,
while the existence of such an internal power of homologous evolution
diminishes the _a priori_ improbability of an analogous law of specific
origination.

All these various considerations have been supplemented by an endeavour to
show the utter inadequacy of Mr. Darwin's theory with regard to the higher
psychical phenomena of man (especially the evolution of moral conceptions),
and with regard to the evolution of individual organisms by the action{225}
of Pangenesis. And it was implied that if Mr. Darwin's latter hypothesis
can be shown to be untenable, an antecedent doubt is thus thrown upon his
other conception, namely, the theory of "Natural Selection."

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