"8. The developmental theory of Darwin is not needed to enable us to
understand the regular harmonious progress of the complete series of
organic forms from the simpler to the more perfect.
"The existence of general laws of Nature explains this harmony, even if
we assume that all beings have arisen separately and independent of one
another. Darwin forgets that inorganic nature, in which there can be no
thought of genetic connexion of forms, exhibits the same regular plan,
the same harmony, as the organic world; and that, to cite only one
example, there is as much a natural system of minerals as of plants and
animals."
We do not feel quite sure that we seize Professor Kolliker's meaning
here, but he appears to suggest that the observation of the general
order and harmony which pervade inorganic nature, would lead us to
anticipate a similar order and harmony in the organic world. And this is
no doubt true, but it by no means follows that the particular order
and harmony observed among them should be that which we see. Surely the
stripes of dun horses, and the teeth of the foetal 'Balaena', are not
explained by the "existence of general laws of Nature." Mr. Darwin
endeavours to explain the exact order of organic nature which exists;
not the mere fact that there is some order.
And with regard to the existence of a natural system of minerals; the
obvious reply is that there may be a natural classification of any
objects--of stones on a sea-beach, or of works of art; a natural
classification being simply an assemblage of objects in groups, so as
to express their most important and fundamental resemblances and
differences. No doubt Mr. Darwin believes that those resemblances and
differences upon which our natural systems or classifications of animals
and plants are based, are resemblances and differences which have been
produced genetically, but we can discover no reason for supposing that
he denies the existence of natural classifications of other kinds.
And, after all, is it quite so certain that a genetic relation may not
underlie the classification of minerals? The inorganic world has not
always been what we see it. It has certainly had its metamorphoses,
and, very probably, a long "Entwickelungsgeschichte" out of a nebular
blastema. Who knows how far that amount of likeness among sets of
minerals, in virtue of which they are now grouped into families and
orders, may not be the expression of the common conditions to which that
particular patch of nebulous fog, which may have been constituted by
their atoms, and of which they may be, in the strictest sense, the
descendants, was subjected?
It will be obvious from what has preceded, that we do not agree with
Professor Kolliker in thinking the objections which he brings forward
so weighty as to be fatal to Darwin's view. But even if the case were
otherwise, we should be unable to accept the "Theory of Heterogeneous
Generation" which is offered as a substitute. That theory is thus
stated:--
"The fundamental conception of this hypothesis is, that, under the
influence of a general law of development, the germs of organisms
produce others different from themselves. This might happen (1) by
the fecundated ova passing, in the course of their development, under
particular circumstances, into higher forms; (2) by the primitive and
later organisms producing other organisms without fecundation, out of
germs or eggs (Parthenogenesis)."
In favour of this hypothesis, Professor Kolliker adduces the well-known
facts of Agamogenesis, or "alternate generation"; the extreme
dissimilarity of the males and females of many animals; and of the
males, females, and neuters of those insects which live in colonies:
and he defines its relations to the Darwinian theory as follows:--"It
is obvious that my hypothesis is apparently very similar to Darwin's,
inasmuch as I also consider that the various forms of animals have
proceeded directly from one another. My hypothesis of the creation of
organisms by heterogeneous generation, however, is distinguished very
essentially from Darwin's by the entire absence of the principle of
useful variations and their natural selection: and my fundamental
conception is this, that a great plan of development lies at the
foundation of the origin of the whole organic world, impelling the
simpler forms to more and more complex developments. How this law
operates, what influences determine the development of the eggs and
germs, and impel them to assume constantly new forms, I naturally cannot
pretend to say; but I can at least adduce the great analogy of the
alternation of generations. If a 'Bipinnaria', a 'Brachialaria', a
'Pluteus', is competent to produce the Echinoderm, which is so widely
different from it; if a hydroid polype can produce the higher Medusa;
if the vermiform Trematode 'nurse' can develop within itself the very
unlike 'Cercaria', it will not appear impossible that the egg, or
ciliated embryo, of a sponge, for once, under special conditions, might
become a hydroid polype, or the embryo of a Medusa, an Echinoderm."
It is obvious, from these extracts, that Professor Kolliker's hypothesis
is based upon the supposed existence of a close analogy between the
phenomena of Agamogenesis and the production of new species from
pre-existing ones. But is the analogy a real one? We think that it is
not, and, by the hypothesis, cannot be.
For what are the phenomena of Agamogenesis, stated generally? An
impregnated egg develops into an asexual form, A; this gives rise,
asexually, to a second form or forms, B, more or less different from A.
B may multiply asexually again; in the simpler cases, however, it does
not, but, acquiring sexual characters, produces impregnated eggs from
whence A, once more, arises.
No case of Agamogenesis is known in which, WHEN A DIFFERS WIDELY FROM B,
it is itself capable of sexual propagation. No case whatever is known
in which the progeny of B, by sexual generation, is other than a
reproduction of A.
But if this be a true statement of the nature of the process of
Agamogenesis, how can it enable us to comprehend the production of
new species from already existing ones? Let us suppose Hyaenas to have
preceded Dogs, and to have produced the latter in this way. Then the
Hyena will represent A, and the Dog, B. The first difficulty that
presents itself is that the Hyena must be asexual, or the process will
be wholly without analogy in the world of Agamogenesis. But passing over
this difficulty, and supposing a male and female Dog to be produced at
the same time from the Hyaena stock, the progeny of the pair, if the
analogy of the simpler kinds of Agamogenesis* is to be followed, should
be a litter, not of puppies, but of young Hyenas. ([Footnote] * If,
on the contrary, we follow the analogy of the more complex forms of
Agamogenesis, such as that exhibited by some 'Trematoda' and by the
'Aphides', the Hyaena must produce, asexually, a brood of asexual Dogs,
from which other sexless Dogs must proceed. At the end of a certain
number of terms of the series, the Dogs would acquire sexes and generate
young; but these young would be, not Dogs, but Hyaenas. In fact, we have
DEMONSTRATED, in Agamogenetic phenomena, that inevitable recurrence
to the original type, which is ASSERTED to be true of variations in
general, by Mr. Darwin's opponents; and which, if the assertion could
be changed into a demonstration would, in fact, be fatal to his
hypothesis.) For the Agamogenetic series is always, as we have seen, A:
B: A: B, etc.; whereas, for the production of a new species, the series
must be A: B: B: B, etc. The production of new species, or genera, is
the extreme permanent divergence from the primitive stock. All known
Agamogenetic processes, on the other hand, end in a complete return to
the primitive stock. How then is the production of new species to be
rendered intelligible by the analogy of Agamogenesis?
The other alternative put by Professor Kolliker--the passage of
fecundated ova in the course of their development into higher
forms--would, if it occurred, be merely an extreme case of variation in
the Darwinian sense, greater in degree than, but perfectly similar in
kind to, that which occurred when the well-known Ancon Ram was developed
from an ordinary Ewe's ovum. Indeed we have always thought that Mr.
Darwin has unnecessarily hampered himself by adhering so strictly to his
favourite "Natura non facit saltum." We greatly suspect that she does
make considerable jumps in the way of variation now and then, and that
these saltations give rise to some of the gaps which appear to exist in
the series of known forms.
Strongly and freely as we have ventured to disagree with Professor
Kolliker, we have always done so with regret, and we trust without
violating that respect which is due, not only to his scientific eminence
and to the careful study which he has devoted to the subject, but to the
perfect fairness of his argumentation, and the generous appreciation of
the worth of Mr. Darwin's labours which he always displays. It would be
satisfactory to be able to say as much for M. Flourens.
But the Perpetual Secretary of the French Academy of Sciences deals with
Mr. Darwin as the first Napoleon would have treated an "ideologue;"
and while displaying a painful weakness of logic and shallowness of
information, assumes a tone of authority, which always touches upon the
ludicrous, and sometimes passes the limits of good breeding.