Genesis of Species
The presence of wild varieties and the difficulty which often exists in the determination of species are sometimes adduced as arguments that high forms are now in process of evolution. These facts, however, do not necessarily prove more than that some species possess a greater variability than others, and (what is indeed unquestionable) that species have often been unduly multiplied by geologists and botanists. It may be, for example, that Wagner was right, and that all the American monkeys of the genus cebus may be reduced to a single species or to two.
With regard to the lower organisms, and supposing views recently advanced to become fully established, there is no reason to think that the forms said to be evolved were new species, but rather reappearances of definite kinds which had appeared before and will appear again under the same conditions. In the same way, with higher forms similar conditions must educe similar results, but here practically similar conditions can rarely obtain because of the large part which “descent” and “inheritance” always play in such highly organized forms.
Still it is conceivable that different combinations at different times may have occasionally the same outcome just as the multiplications of different numbers may have severally the same result.
There are reasons, however, for thinking it possible that the human race is a witness of an exceptionally unchanging and stable condition of things, if the calculations of Mr. Croll are valid as to how far variations in the eccentricity in the earth’s orbit together with the precession of the equinoxes have produced changes in climate. Mr. Wallace has pointed out that the last 60,000 years having been exceptionally unchanging as regards these conditions, specific evolution may have been exceptionally rare. It becomes then possible to suppose that for a similar period stimuli to change in the manifestation of animal forms may have been exceptionally few and feeble,—that is, if the conditions of the earth’s orbit have been as exceptional as stated. However, even if new species are actually now being evolved as actively as ever, or if they have been so quite recently, no conflict thence necessarily arises with the view here advocated. For it by no means follows that if some examples of new species have recently been suddenly produced from individuals of antecedent species, we ought to be able to put our fingers on such cases; as Mr. Murphy well observes in a passage before quoted, “If a species were to come suddenly into being in the wild state, as the Ancon sheep did under domestication, how could we ascertain the fact? If the first of a newly-born species were found, the fact of its discovery would tell nothing about its origin. Naturalists would register it as a very rare species, having been only once met with, but they would have no means of knowing whether it were the first or the last of its race.”
But are there any grounds for thinking that in the genesis of species an internal force or tendency interferes, co-operates with and controls the action of external conditions?
It is here contended that there are such grounds, and that though inheritance, reversion, atavism, Natural Selection, &c., play a part not unimportant, yet that such an internal power is a great, perhaps the main, determining agent.
It will, however, be replied that such an entity is no vera causa; that if the conception is accepted, it is no real explanation; and that it is merely a roundabout way of saying that the facts are as they are, while the cause remains unknown. To this it may be rejoined that for all who believe in the existence of the abstraction “force” at all, other than will, this conception of an internal force must be accepted and located somewhere—cannot be eliminated altogether; and that therefore it may as reasonably be accepted in this mode as in any other.
It was urged at the end of the third chapter that it is congruous to credit mineral species with an internal power or force. By such a power it may be conceived that crystals not only assume their external symmetry, but even repair it when injured. Ultimate chemical elements must also be conceived as possessing an innate tendency to form certain unions, and to cohere in stable aggregations. This was considered towards the end of Chapter VIII.
Turning to the organic world, even on the hypothesis of Mr. Herbert Spencer or that of Mr. Darwin, it is impossible to escape the conception of innate internal forces. With regard to the physiological units of the former, Mr. Spencer himself, as we have seen, distinctly attributes to them “an innate tendency” to evolve the parent form from which they sprang. With regard to the gemmules of Mr. Darwin, we have seen, in Chapter X., with how many innate powers, tendencies, and capabilities they must each be severally endowed, to reproduce their kind, to evolve complex organisms or cells, to exercise germinative affinity, &c.
If then (as was before said at the end of Chapter VIII.) such innate powers must be attributed to chemical atoms, to mineral species, to gemmules, and to physiological units, it is only reasonable to attribute such to each individual organism.
The conception of such internal and latent capabilities is somewhat like that of Mr. Galton, before mentioned, according to which the organic world consists of entities, each of which is, as it were, a spheroid with many facets on its surface, upon one of which it reposes in stable equilibrium. When by the accumulated action of incident forces this equilibrium is disturbed, the spheroid is supposed to turn over until it settles on an adjacent facet once more in stable equilibrium.
The internal tendency of an organism to certain considerable and definite changes would correspond to the facets on the surface of the spheroid.
It may be objected that we have no knowledge as to how terrestrial, cosmical and other forces can affect organisms so as to stimulate and evolve these latent, merely potential forms. But we have had evidence that such mysterious agencies do affect organisms in ways as yet inexplicable, in the very remarkable effects of geographical conditions which were detailed in the third chapter.
It is quite conceivable that the material organic world may be so constituted that the simultaneous action upon it of all known forces, mechanical, physical, chemical, magnetic, terrestrial, and cosmical, together with other as yet unknown forces which probably exist, may result in changes which are harmonious and symmetrical, just as the internal nature of vibrating plates causes particles of sand scattered over them to assume definite and symmetrical figures when made to oscillate in different ways by the bow of a violin being drawn along their edges. The results of these combined internal powers and external influences might be represented under the symbol of complex series of vibrations (analogous to those of sound or light) forming a most complex harmony or a display of most varied colours. In such a way the reparation of local injuries might be symbolized as a filling up and completion of an interrupted rhythm. Thus also monstrous aberrations from typical structure might correspond to a discord, and sterility from crossing be compared with the darkness resulting from the interference of waves of light.
Such symbolism will harmonize with the peculiar reproduction, before mentioned, of heads in the body of certain annelids, with the facts of serial homology, as well as those of bilateral and vertical symmetry. Also, as the atoms of a resonant body may be made to give out sound by the juxtaposition of a vibrating tuning-fork, so it is conceivable that the physiological units of a living organism may be so influenced by surrounding conditions (organic and other) that the accumulation of these conditions may upset the previous rhythm of such units, producing modifications in them—a fresh chord in the harmony of nature—a new species!
But it may be again objected that to say that species arise by the help of an innate power possessed by organisms is no explanation, but is a reproduction of the absurdity, l’opium endormit parcequ’il a une vertu soporifique. It is contended, however, that this objection does not apply, even if it be conceded that there is that force in Moliere’s ridicule which is generally attributed to it. Much, however, might be said in opposition to more than one of that brilliant dramatist’s smart philosophical epigrams, just as to the theological ones of Voltaire, or to the biological one of that other Frenchman who for a time discredited a cranial skeletal theory by the phrase “Vertebre pensante.”
In fact, however, it is a real explanation of how a man lives to say that he lives independently, on his own income, instead of being supported by his relatives and friends. In the same way, there is fully as real a distinction between the production of new specific manifestations entirely ab externo, and by the production of the same through an innate force and tendency, the determination of which into action is occasioned by external circumstances.
To say that organisms possess this innate power, and that by it new species are from time to time produced, is by no means a mere assertion that they are produced, and in an unknown mode. It is the negation of that view which deems external forces alone sufficient, and at the same time the assertion of something positive, to be arrived at by the process of reductio ad absurdum.
All physical explanations result ultimately in such conceptions of innate power, or else in that of will force. The far-famed explanation of the celestial motions ends in the conception that every particle of matter has the innate power of attracting every other particle directly as the mass, and inversely as the square of the distance.