The fact is that every organic form, whether plant or animal, derived from the protoplasmic compounds of carbon-dixoide, ammonia and water, is, as Mr. Drummond puts it,[[14]] "made of materials which have once been inorganic. An organizing principle, not belonging to their kingdom, lays hold of them and elaborates them."
Thus by the introduction of LIFE we have a vastly enlarged horizon. Before, in the organic world, we had only the "principle" of solidifying or crystallizing, liquefying, and turning to gas or vapour, ever stopping when the state was attained. Or if a combination was in progress, still the result was only a rearrangement of the same bulk of materials (however new the form) in solid, liquid, or gas, but no increase, no nutrition, no reproduction. In the organic world we have something so different, that whether we talk of "property" or "principle," the things are entirely distinct.
The essential difference, stated as regards the mere facts of irritability or motion, nutrition and reproduction, is so grandly sufficient in itself, that one almost regrets to have to add on the other facts which further emphasize the distinction between life and any property of matter. But these further facts are highly important as regards another part of the argument. For while what has just been said almost demonstrates the necessity of a Giver of Life from a kingdom outside the organic, the further facts point irresistibly to the conclusion that we must predicate more about the Giver of Life that we can of an abstract and unknown Cause.
The original protoplasm, when dead, is undistinguishable by the eye, by chemical test, or by the microscope, from the same protoplasm when living; and living protoplasm, again, may be either animal or vegetable. Both are in every respect (externally) absolutely identical. Yet the one will only develop into a plant, the other only into an animal. Nor does it diminish the significance of the fact to say that the differentiation is now fixed by heredity. If we suppose protoplasm to be only a fortuitous combination of elements, what secondary or common natural cause will account for its acquisition of the fixed difference? It is true that some forms of plants exhibit some functions that closely approach the functions of what we call animal life; but, as we shall see presently, there is no evidence whatever that there is any bridge between the two—we have no proof that a plant ever develops into an animal. Here is one of the gaps which the theory of Evolution, true as it is to a certain extent, cannot bridge over; and we must not overlook the fact. We shall revert to it hereafter.
Can it be believed, then, that protoplasm, as the origin of life, is self-caused, and self-developed? And this is not all. I must briefly remind my readers that the way in which animal protoplasm deals with the elements of nutrition is quite opposite to that which plant protoplasm follows. I might, indeed, have mentioned this at an earlier stage, when I mentioned Professor Huxley's comparison of the chemical action in the formation of water with what he assumed to be the case in the formation of protoplasm. When water is formed, the two gases disappear, and an exactly equal weight of water appears in their place; but if living protoplasm is enabled to imbibe liquid or other nutriment containing ammonia, water, and carbonic acid, there is no disappearance of the three elements and an equivalent weight of living protoplasm appearing in its place. Protoplasm consumes the oxygen and sets free the carbonic acid. Both kinds of protoplasm do this, until exposed to the light; and then a difference is observed; for under the influence of light, animal protoplasm alone continues to act in this way, and vegetable protoplasm begins at once to develop little green bodies or corpuscles in its cells, and afterwards acts in a totally opposite way, taking the carbon into its substance and giving off the oxygen.[[15]]
Not only then has each kind of protoplasm its own mysterious character impressed on it, and is compelled to act in a certain way; but still further, each particle of animal and vegetable protoplasm, when directed into its general course of development as plant or animal, will again only obey a certain course of development in its own line.
But we must proceed a step further; for those who would believe in the sufficiency of unaided Evolution, bid us bear in mind how very elementary the dawn of instinct or the beginning of reason is in the lowest forms which are classed as animal, and how very small is the gap[[16]] between some highly organized plants and some animal forms, and argue therefore that they may justly regard the distinction as of minor importance, and hope that the "missing link" will be yet discovered and proved. At any rate, they minimize the difference, and urge that it is of no account if at least they can establish the sufficiency of a proved development extending unbroken from the lowest to the highest animal form. And having fixed attention on this side, no doubt there is a long stretch of smooth water over which the passage is unchecked.
The Evolution theory is that all the different species of animals, birds, and other forms of life have been caused by the accumulation and perpetuation of numerous small changes which began in one or at most a few elementary forms, and went on till all the thousands of species we now know of were developed.[[17]] It is a fact that all organic forms have a certain tendency to vary. I need only allude to the many varieties of pigeons, horses, cattle, and dogs which are produced by varying the food, the circumstances of life and so forth, and by selective breeding.
The contention then is: given certain original simple forms of life, probably marine or aquatic—for it is in the water that the most likely occur—these will gradually change and vary, some in one direction, some in another; that the changes go on increasing, each creature giving birth to offspring which exhibits the stored-up results of change, till the varied and finished forms—some reptile, some bird, some animal—which we now see around us, have been produced. And at last man himself was developed in the same way. All this, observe, is by the action of just such ordinary and natural causes as we now see operating around us—changes in food and in climate, changes in one part requiring a corresponding change in others, and so on.
Nature contains no sharply drawn lines. Plants are different from animals; but there are animals so low down in the scale of life that it is difficult to distinguish them from plants. Pigeons are distinct from pheasants, but the line at which the one species ends and the other begins is difficult to draw. This fact seems to invite some theory of one form changing into other. Accordingly the evolutionist explains the working of the process which he asserts to be sufficient to produce all the various forms of life in our globe.