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The great and well-deserved fame of Darwin has eclipsed the brilliancy of these services; but although Darwin had been at work in the same field long before Mr. Wallace, and only delayed publication in order to perfect a system which Mr. Wallace had but outlined, it ought not to be forgotten that these two essays were printed, the first four years, and the latter one year, before the "Origin of Species."

There is still one illustrious name which will always deserve prominence in connection with the present subject. In his work on "Comparative Anatomy and Physiology of Vertebrates" Professor Owen writes: "Each successive parcel of geological truth has tended to dissipate the belief in the unusually sudden and violent nature of the changes recognisable in the earth's surface. In specially directing my attention to this moot-point, whilst engaged in investigations of fossil remains and in the reconstruction of the species to which they belonged, I was at length led to recognise one cause of extinction as being due to defeat in the contest which, as a living organised whole, the individual of each species had to maintain against the surrounding agencies which might militate against its existence. Mr. Darwin aims to apply it [this principle] not only to the extinction, but to the origin of species.” 1

Professor Owen, without either admitting or adopting Darwin's application of this secondary law to the origin of species, is perfectly justified in affirming "that the 'admission' or 'adoption' was, in whatever degree it might relate to the Darwinian theory, an anticipation;" for whilst Darwin first promulgated his theory in 1857 (he did not publish it till 1859), Professor Owen, as early as February 1850,2 had exemplified the principle of the preservation of the favoured race by noting the conditions under which the battle of life is fought. "If," said he, "a dry season be gradually prolonged, the large mammal will suffer from the drought sooner than the small one; if such 1 Vol. iii. p. 798. 2 Zoological Transactions, vol. iv. p. 15.

alteration of climate affect the quantity of vegetable food, the bulky herbivore will first feel the effects of stinted nourishment; if new enemies are introduced, the large and conspicuous quadruped or bird will fall a prey, whilst the smaller species conceal themselves and escape. Smaller animals also are usually more prolific than large ones.'

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The strength of the argument for natural selection, great as its prima facie probability is at once seen to be, is enormously enhanced by the mass of facts which its champions have brought to bear upon it. There are difficulties, no doubt, which at present it has to overleap; but in the hands of its original propounders objections melt away, and not unfrequently come to further what they had once appeared to impede. The facts themselves, and indeed the treatment of the whole subject by Darwin and Mr. Wallace, are more fascinating than any work of fiction. Details are beyond the compass of my design, nor will you be offered dry abstractions in the place of them. I shall endeavour to set forth some of the strongest features of the theory, together with some of its weakest. Meanwhile it behoves us to refer to the beginnings of life, which Darwin does not deal with, and with which natural selection has, in the present state of our knowledge, but remote concern.

1 Comparative Anatomy, &c., p. 799.

LETTER V.

WHATEVER may be the ultimate issue in days to come of the generatio equivoca controversy, we have pretty strong grounds for the assumption that, upon this earth at least, life must have had a beginning some time or other. Without placing too much reliance upon the nebular hypothesis or upon the central fluidity of our planet—which cannot be called an established truth-earthquakes, thermal springs, geysers, volcanoes, and the certain though irregular increase of heat with depth, prove almost beyond a doubt that the surface of the earth is a very thin crust covering matter in a state of igneous fusion. Although geology is silent on the question of complete original fluidity, astronomy favours the speculation; while the theory of solidification by cooling, as applied to the earth's surface, has the full approval of science.

If, then, we may suppose that temperature continues to increase at the known rate of something like 1° Fahr. for every 65 to 70 feet, in two miles we should reach the level of our boiling springs; and at a depth of 34 miles should reach the melting-point of iron. Adopting then the cooling hypothesis in explanation of the crust, what is now the melting-point of iron might formerly have been 100 times hotter, and even the surface itself hot enough to convert metals into vapour. It is evident that, under anything approaching such conditions, life could not have existed. In the first place, the excessive molecular vibration would have rendered the necessary chemical combination impossible. Secondly, water, which enters so largely into the composition of all organisms, could not

have been formed until the temperature had fallen below that only two miles beneath our present surface. Whence then did life originate? Are we to look for its beginning in natural causes, or shall we resort to miracle ?

In the latest of his published opinions, Professor Du Bois-Reymond counts the origin of life as one of the seven world-riddles, the ultimate solution of which he believes to be transcendental. "Transcendental," because although he maintains that we are logically bound to admit the mechanical origin of life (which, as Zöllner and Häckel declare, can only be denied by denying the universality of causation), nevertheless the question of life's beginning inevitably forces us back upon the prior questions of the beginning of motion and the existence of Matter and Force. "Once matter had begun to move, worlds might arise: under appropriate conditions, which we are as little able to imitate as those under which a mass of inorganic results occur, the peculiar state of dynamical equilibrium of matter, which we call life, may come into existence."1 But we must first have matter in motion; and here we reach the limits of scientific inquiry, and are face to face with the transcendent.

The evolutionist must postulate something to evolve. The pied-à-terre of his theory is matter in a nebulous state, which has gradually condensed by gravitation. This nebular hypothesis, of which we shall have to speak hereafter, carries with it the supposition that condensation is the original cause of the earth's heat. If so, then of the sun's heat of the heat, in short, of our entire system. But where were the germs of life during the "cosmological gas" period? Two conclusions are open to us: If life had no beginning in time-if there was always a life-supporting world somewhere in the universe, then the nebular hypothesis, as a cosmical theory, is false. If life had a beginning, then, inasmuch as life implies sensation and consciousness, its beginning is unintelligible: in other words, the 1 Die Sieben Welträthsel, 1882.

laws of mechanics will not account for feeling, and the problem of life is transcendental. To this, however, we shall return. Meanwhile, we may notice the attempts that have been made to settle the question empirically. Can life be produced in the laboratory?

Of course you are aware that between organic and inorganic matter there is no radical difference. The same elements are common to both, their combination only being more complex in one case than in the other. The indefinite complexity of the organic compounds explains (from the chemical point of view) the corresponding complexity of organic phenomena. Well, say you, if chemistry recognises no essential difference between organic and inorganic, biology does: life is associated with one, and not with the other: here is something more than an artificial distinction. Precisely so. On this earth there is no life save in conjunction with organic compounds. We may imagine if we please that life is something distinct from the compounds, and added to the chemical elements after they have combined in a particular manner. All we know is, vital phenomena never appear until the combination is effected. Why certain elements combine in such a way, or why, when combined, life begins to be manifested, is more than any one can tell. From the green scum on a stagnant pool up to man, and through the whole scale of living things which divide them, one fundamental substance constitutes the living matter or germ of life in all. This substance is known by the vague name of Protoplasm, i.e., original matrix. Life is said to be one of the properties evolved from it; or, more correctly speaking, evolved with it.

Protoplasm is a semifluid gelatinous compound, consisting mainly of water, ammonia, and carbonic acid; out of which ingredients it is procreated by plants, and so becomes the substance of the plant itself. When in turn the plant becomes the food of an animal, the protoplasm,

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