II.]

Thomson's Vortex Atoms.

73

I must not leave this subject of the structure of matter without mentioning the remarkable suggestion which Sir William Thomson has made as to the possibility of having true physical atoms, pieces which cannot be cut, without ascribing to them the inconceivable property of infinite hardness. The idea is that an atom is a vortex ring, or other form of vortex movement-the same kind of movement as a smoker sometimes produces in the smoky air which issues from his lips-but the vortices which form the atoms of matter exist, according to Thomson, in a continuous fluid filling all space, and destitute of internal friction. If this is the character of the atom, nothing short of an act of creative power could produce it, even when the raw material, so to speak, that is the continuous fluid, was given. And, again, nothing short of a miraculous or non-natural intervention could bring the vortex to rest after once it was set in motion. On this theory, even if we were supplied with as much of the raw material of atoms as we chose to ask for the clay of which our bricks are made-we should be powerless to add one to the number of atoms already existing or to reduce their number by one. This is because the fluid in which the vortex movement is supposed to exist is frictionless: but if we suppose instead that it is nearly but not quite frictionless, we get two very curious results. For then, in the first place, can we conceive of the development of matter out what is not matter (I say conceive of it-nothing more than that, for we have no means of picturing the process to our minds, and not a particle of evidence that such a process ever occurs). And further, we should then be able to extend our vision into the future of the universe in a very wonderful way: for if the atoms are vortices in a fluid which possesses ever so little viscosity, they must in time die out altogether, and so we should be able to predict the total disappearance of matter itself! The doctrine of the dissipation of energy has led us,

74

Possible disappearance of gross matter. [LECT.

with much certainty, to conclude that the end of globe development will be a huge inert mass, in which all the matter of the worlds shall be gathered together; but the speculation I am now reproducing takes us a long way further than that. It takes us to a time when, one after another, the atoms shall melt into space-to a time when "we shall have no huge useless inert mass existing to remind the passer-by [if there be a passer-by] of a form of energy and a species of matter that is long since out of date "-to a time when the universe shall have buried its dead out of sight. It will at least serve to bring vividly before us the feebleness of our faculties, if we conceive of the visible universe itself as nothing more than a collection of tiny whirlpools, which a little while ago were not, and a little later will sink to rest; and yet in their brief moment of being we find the best help we know of in our attempts to realize that infinite duration which is an attribute of God.

But we must come down from those high regions of physical dream-land to more sober ground. We find on the surface of the earth many different kinds of living things, and it is a part of the business of science to trace the historical connection between what we see now and the much earlier stage in the earth's existence to which a consideration of globe development brought us-the stage, namely, when the surface had just cooled sufficiently to allow animals and plants to live. In other words we must consider the evolution or development of life. And the question at once arises, were the various forms of living things which now exist separately created, or were they developed from some more primitive form, as the suns and planets have been developed from nebulæ ? Long before the time of Darwin, naturalists advanced the hypothesis that the various species have sprung from a common stock; but it was left to Darwin

1The Unseen Universe (Stewart and Tait), p. 119.

II.] Life Development by Artificial Selection.

75

and Wallace, and especially Darwin, to take the truly immense step of reducing the speculation to a scientific theory, and to show how, by natural means, such a process of descent may have occurred. The theory of descent, and the explanation of that theory by reference to natural selection, are contributions to science whose importance cannot easily be overrated. For the benefit of those now present whose knowledge of Life Development is even more imperfect than my own, I shall endeavour to give an outline of it, though, as the subject is one out of the range of my own studies, such an outline will most likely be faulty as well as incomplete.

Along with the fact that children resemble their parents, we find that this resemblance is not exact, that they differ more or less from their parents and from each other. The fact of the likeness to parents is called Heredity, the fact of the unlikeness is called Variation. Thus, amongst say the descendants of a pair of sheep, we will find some with longer bodies and shorter legs than others. And it will occasionally happen that the difference is so great as to have a large influence on the habits of the animal. For example, if a sheep is born with an unusually long body and short legs, it will not be able to jump over fences which other sheep can jump over, and some of its children will share this peculiarity while others will not. Suppose, then, that the farmer who owns the sheep sees the benefit of having a flock which will stay at home; he can take advantage of heredity to breed a race with long bodies and short legs. He can do this by letting the common kind die without offspring, and encouraging the breeding of the long-bodied sheep; and in course of time all his flock will be of the long-bodied kind. Now this is not a fancy picture: it is the real story of what a real farmer once did, a "cute' Yankee of Massachusetts.

We see here how a new and permanent variety of living beings may arise by a process of artificial selection; but when

76 Development of Species by Natural Selection. [LECT.

we attempt to explain all the actual distinctions of species and genera as accumulated results of similar small changes, we must look for some determining agency other than New England farmers. Darwin supplies the want by pointing to the Struggle for Existence, the battle of life in which individual fights with individual and race with race-fights simply to live, and the weaker goes to the wall. Now, if small variations occur which give to the possessors of them some advantage, however little, in this universal struggle, these individuals will stand a greater chance of success than their less fortunate neighbours. They are more likely to thrive and propagate their kind. Any peculiarity which makes an animal or a plant better suited to the circumstances of its existence will tend to become permanent and to be intensified in succesive generations; while those individuals, otherwise similar and exposed to the same conditions, but who do not possess the same peculiarity, will tend to die out. And besides the changes which occur from generation to generation, it is observed that within the life-time of a single individual there is an adaptation of its organism to the conditions of its life, and this too, by heredity, tends to be passed on to its successors. You will readily see that this process of Natural Selection takes advantage not only of such considerable variations as those we had an example of in the case of the sheep, but also of such minor variations as occur at every birth and in the lifetime of every individual. And as time goes on the successive small differences are added together, and hence it is easy to imagine that in the course of ages very great changes will result. In this way, then, it is conceivable that a man, a bird and a fish may have had a common ancestor, one of whose progenitors was perhaps also the remote grand-parent of a starfish or a worm. And, indeed, so ill-defined-so impossible of definition-appears to be the boundary between plant and animal life, that we need not be surprised if the pine and the bamboo

II.]

Cellular Structure.

77

succeed in making good a claim to cousinship with man. Thus the more advanced followers of Darwin have endeavoured to trace the pedigree of the human species down through lower forms of animal life, forms not necessarily the same as those now extant, to a primitive creature belonging to the class which Haeckel calls "not only the simplest of all observed organisms, but even the simplest of all imaginable organisms.”1

But this is not by any means the whole of the story. Biologists tell us that if we examine a very simple form of living creature-the Amaba, we shall find it to consist of a little lump of soft material, which perpetually changes its form in response to the stimuli which reach it from outside. A central part somewhat firmer than the rest, called the nucleus, is its only apparent approach to organization. But this being is able to perform the three great functions of life: it is irritable, that is, it responds to external influences; it nourishes itself by stretching out parts of its own soft substance as temporary hands to gather in food; and it produces other creatures of its kind, by the simple process of splitting up into two pieces, each of which thenceforth lives an independent life.

Now every more complex organism is found to be built up of a great number of simple pieces grouped together. These simple pieces are called cells, and each of them resembles to some extent an Amoeba. Each of them consists essentially of a little lump of the same soft substance, with a firmer nucleus, and each of them is believed to possess a certain degree of individual life. But they are not wholly independent, for the myriads of cells in the body of one individual work together to maintain the life of that individual, just as the myriads of officials in Japan are component parts of the central government, while each one possesses a certain amount of separate

1 History of Creation, Vol. I, p. 343.