MR. MARTINEAU ON EVOLUTION.

[First published in The Contemporary Review, for June, 1872.]

THE article by Mr. Martineau, in the April number of the Contemporary Review, on "The Place of Mind in Nature, and Intuition of Man," recalled to me a partiallyformed intention to deal with the chief criticisms which have from time to time been made on the general doctrine set forth in First Principles; since, though not avowedly directed against propositions asserted or implied in that work, Mr. Martineau's reasoning tells against them by implication. The fulfilment of this intention I should, however, have continued to postpone, had I not learned that the arguments of Mr. Martineau are supposed by many to be conclusive, and that, in the absence of replies, it will be assumed that no replies can be made. It seems desirable, therefore, to notice these arguments at once-especially as the essential ones may, I think, be effectually dealt with in a comparatively small space.

The first definite objection which Mr. Martineau raises is, that the hypothesis of General Evolution is powerless to account even for the simpler orders of facts in the absence of numerous different substances. He argues that were matter all of one kind, no such phenomena as chemical

changes would be possible; and that, "in order to start the world on its chemical career, you must enlarge its capital and present it with an outfit of heterogeneous constituents. Try, therefore, the effect of such a gift; fling into the pre-existing cauldron the whole list of recognized elementary substances, and give leave to their affinities to work." The intended implication obviously is, that there must exist the separately-created elements before evolution can begin.

Here, however, Mr. Martineau makes an assumption which few, if any, chemists will commit themselves to, and which many will distinctly deny. There are no "recognized elementary substances," if the expression means substances known to be elementary. What chemists, for convenience, call elementary substances, are merely substances which they have thus far failed to decompose; but, bearing in mind past experiences, they do not dare to say that they are absolutely undecomposable. Water was taken to be an element for more than two thousand years, and then was proved to be a compound; and, until Davy brought a galvanic current to bear upon them, the alkalies and the earths were supposed to be elements. So little true is it that "recognized elementary substances" are supposed to be absolutely elementary, that there has been much speculation among chemists respecting the process of compounding and recompounding by which they have been formed out of some ultimate substance-some chemists having supposed the atom of hydrogen to be the unit of composition, but others having contended that the atomic weights of the so-called elements are not thus interpretable. If I remember rightly, Sir John Herschel was one, among others, who, some five-and-twenty years ago, threw out suggestions respecting a system of compounding that might explain these relations of the atomic weights.

What was at that time a suspicion has now become practically a certainty. Spectrum-analysis yields results

wholly irreconcilable with the assumption that the conventionally-named simple substances are really simple. Each yields a spectrum having lines varying in number from two to eighty or more, every one of which implies the intercepting of ethereal undulations of a certain order by something oscillating in unison or in harmony with them. Were iron absolutely elementary, it is not conceivable that its atom could intercept ethereal undulations of eighty different orders. Though it does not follow that its molecule contains as many separate atoms as there are lines in its spectrum, it must clearly be a complex molecule. The evidence thus gained points to the conclusion that, out of some primordial units, the so-called elements arise by compounding and recompounding; just as by the compounding and recompounding of so-called elements there arise oxides, and acids, and salts.

And this hypothesis is entirely in harmony with the phenomena of allotropy. Various substances, conventionally distinguished as simple, have several forms under which they present quite different properties. The semitransparent, colourless, extremely active substance called phosphorus may be so changed as to become opaque, dark red, and inert. Like changes are known to occur in some gaseous, non-metallic elements, as oxygen; and also in metallic elements, as antimony. These total changes of properties, brought about without any changes to be called chemical, are interpretable only as due to molecular rearrangements; and, by showing that difference of property is producible by difference of arrangement, they support the inference otherwise to be drawn, that the properties of different elements result from differences of arrangement arising by the compounding and recompounding of ultimate homogeneous units.

Thus Mr. Martineau's objection, which at best would imply a turning of our ignorance of the nature of elements into positive knowledge that they are simple, is, in fact, to

be met by two sets of evidences, which imply that they are compound.

Mr. Martineau next alleges that a fatal difficulty is put in the way of the General Doctrine of Evolution by the existence of a chasm between the living and the not-living. He says:-"But with all your enlargement of data, turn them as you will, at the end of every passage which they explore, the door of life is closed against them still." Here again our ignorance is employed to play the part of knowledge. The fact that we do not know distinctly how an alleged transition has taken place, is transformed into the assumption that no transition has taken place. We have, in a more general shape, the argument which until lately was thought conclusive-the argument that because the genesis of each species of creature had not been explained, therefore each species must have been separately created.

Merely noting this, however, I go on to remark that scientific discovery is day by day narrowing the chasm, or, to vary Mr. Martineau's metaphor, "opening the door." Not many years since, it was held as certain that the chemical compounds distinguished as organic could not be formed artificially. Now, more than a thousand organic compounds have been formed artificially. Chemists have discovered the art of building them up from the simpler to the more complex, and do not doubt that they will eventually produce the most complex. Moreover, the phenomena attending isomeric change give a clue to those movements which are the only indications we have of life in its lowest forms. In various colloidal substances, including the albuminoid, isomeric change is accompanied by contraction or expansion, and consequent motion; and, in such primordial types as the Protogenes of Haeckel, which do not differ in appearance from minute portions of albumen, the observed motions are comprehensible as accompanying isomeric changes caused by variations in

surrounding physical actions. The probability of this interpretation will be seen on remembering the evidence we have that, in the higher organisms, many functions are essentially effected by isomeric changes from one to another of the multitudinous forms which protein assumes.

Thus the reply to this objection is, first, that there is going on from both sides a narrowing of the chasm supposed to be impassable; and, secondly, that, even were the chasm not in course of being filled up, we should no more be justified in therefore assuming a supernatural commencement of life, than Kepler was justified in assuming that there were guiding-spirits to keep the planets in their orbits, because he could not see how else they were to be kept in their orbits.

The third definite objection made by Mr. Martineau is of kindred nature. The Hypothesis of Evolution is, he thinks, met by the insurmountable difficulty that plant life and animal life are absolutely distinct. "You cannot," he says, "take a single step toward the deduction of sensation and thought: neither at the upper limit do the highest plants (the exogens) transcend themselves and overbalance into animal existence; nor at the lower, grope as you may among the sea-weeds and sponges, can you persuade the sporules of the one to develop into the other."

This is an extremely unfortunate objection to raise. For, though there are no transitions from vegetal to animal life at the places Mr. Martineau names, where, indeed, no biologist would look for them; yet the connexion between the two great kingdoms of living things is so complete that separation is now regarded as impossible. For a long time naturalists endeavored to frame definitions such as would, the one include all plants and exclude all animals, and the other include all animals and exclude all plants. But they have been so repeatedly foiled in the attempt that they have given it up. There is no chemical distinction