organism that protect one from present physical evils, whether it be peculiarities that indicate progression or retrogression. Indeed, the very opposite qualities might secure immunity from destruction. A large dog might jump over a fence where a small one would go through, and only the medium sized be kept in by it. A nervous animal might live where a stupid one would die, and vice versa.

XVIII. THE STRUGGLE FOR LIFE.

In enumerating these changes in external nature, we have brought before us only one of the known agencies which serve as a crucible in which to test the tenacity of the life of any organic form. Whatever may be the ultimate explanation of it, it is a fact that the "whole creation groaneth and travaileth together in pain until now." There is a constant state of warfare in the organic world. The grub is trying to kill the tree, and the woodpecker is seeking, with exquisite instruments, to take the life of the grub; the parasite is worrying the life of the woodpecker, and so on through the whole story of the house that Jack built.

The Malthusian law of the tendency of all living things to increase through reproduction in geometrical ratio, while the stores from which they feed and the houses in which they live are limited by definite measurements, becomes in Darwin's hands a mighty power. If slow breeding man were not limited by many unavoidable evils from increasing and multiplying according to his natural instincts, there would in a few thousand years be so many people in the world that standing-room could not be found for them. If a plant should produce two seedlings a year, and its two produce each two more, and so on, there would in twenty years be a million. plants. Mr. Darwin says: "The elephant is reckoned to be the slowest breeder of all known animals, and I have taken some pains to calculate its probable minimum rate of natural increase; it will be under the mark to assume that it breeds when thirty years old, and goes on breeding till ninety years

1

1 Origin of Species (5th ed.), p. 51.

old, bringing forth three pairs of young in this interval; if this be so, at the end of the fifth century there would be alive fifteen million elephants, descended from the first pair." When now we come to consider the rapidity with which innumerable other organisms tend to increase, we shall have before us a faint idea of the power that is here brought into the equation. We may safely assume that plants produce every year a million times as many seeds fitted for growth, as ever come to perfection. So that the ground of a forest is year by year literally covered with seedlings that are destined to die from lack of room and want of access to the elements necessary to their growth. Of the smaller plants we know that the ground is full of their seeds. Turn up the ground where you will, and it will be found that there are germs of life in it, or that they will lodge on it, and cover it very speedily with a rank vegetation. A few rank weeds, like the burdock or the thistle, delight to lord it over their weaker brethren. Infanticide and oppression are, in a figure, practised to an alarming extent throughout the vegetable kingdom. "Plants do not grow where they like best, but where other plants will let them."

Animals have feeling, which plants have not. But of compassion the animal kingdom is utterly devoid. The equilibrium of the animal world is maintained not merely by preparation for war, but by actual and unceasing conflict. Almost every species of animal is pressing beyond the limits of its means of subsistence. There are low forms of animals that produce millions of young every season. Yet the number of progeny which survive may not be at all in proportion to that which comes into existence. The mishaps that befall a young trout are far more numerous than those to which a whale is liable. "The condor lays a couple of eggs, and the ostrich a score; and yet in the same country the condor may be the more numerous of the two. The fulmar petrel lays but one egg, yet it is believed to be the most numerous bird in the world." It is plain that the number of individuals of a species that are found in existence is not at all

in proportion to their natural tendency to increase, but is rather dependent on their ability to contend against forces, both organic and inorganic, which oppose them after they are brought into existence. The great difficulty to be overcome in the continual existence of a species is that of adjusting itself to the other forms of life that crowd in upon it.

There is a constant oscillation in the comparative numbers of different classes of animals. As the food of herbivorous animals for any cause increases, the law of geometrical increase soon fills the enlarged possibility of subsistence, and individuals of this order are in competition again with each other. But the increase of Herbivora is soon followed by that of the Carnivora who feed upon them till these two orders are again in sharp competition, and the Carnivora contend with a diminishing relative supply of food.

When the animals are superabundant upon which the Carnivora feed, the weakest and most clumsy of that order could supply himself with food, and it would be the most helpless of the Herbivora that would be devoured. But when the balance was restored and the competition commenced again, the fleetest or strongest of the Herbivora, or those that had some other advantage, would be preserved; only the more favored of the Carnivora could then take or overcome them. The unfortunate of both orders would perish, and the more favored ones of both survive. Somewhat thus must be the internal contest among the animals which are food one for the other. When the struggle is in the same family with lessening amount of food, either absolute or relative, or with changing climate, analogous results must follow. In both cases, those variations from the type of the species that occur in every individual are the centrifugal force tending to divergence, counteracted, when nothing else interferes to augment it, by the law of inheritance and by the inter-crossing of individuals with opposite variations.

The external power in nature which supplies the place of man's agency as seen in domesticating animals, is the varying conditions of life which arise from changes in climate,

in temperature, in the extent of territory open for the range of the species, together with the encroachment of other species upon their domain. In this complicated environment we have a power which Darwin personifies as "Natural Selection." He speaks, we suppose, of power in the secondary sense, as when we use similar language regarding the force of gravity. He proceeds to trace the action of this secondary cause with reference to the production of species, as geologists would try to account for the features of a river valley by the erosive action of flowing water; or as the mathematician verifies the law of gravitation by the solutions it affords to the complicated observations of the astronomer. Or yet again, the problem is similar to that of the historian who sits in judgment on the documents before him, and pronounces them true or false according as they conform or not, to the known action of the human mind under the stress of given motives.

It should be remembered in this connection that the limits which we have set to the liberty of variation inherent in species is altogether arbitrary. It is perfectly proper for any person to proceed according to the law of parsimony from what is actually known of the variability of species and of the power of "Natural Selection," and see how far these factors will account for all the changes that are apparent. To the theologian the question regards the mode of the divine operations in nature. Darwin's law of "Natural Selection" only furnishes a natural bond for what Agassiz calls the ideas of God that were realized in innumerable special creations, and during countless periods of past time.

The theologian stands in no more need of miracles for the production of species than he does for that of the planets and their movements. Direct providential interposition is not for the irrational creation, but for the rational. So we may divest ourselves of theological prepossessions of any kind in reference to the material machinery by which the diversity of animal and vegetable life has been produced. But of these points we will speak farther on.

XIX. TIME AS A FACTOR IN THE EQUATION.

The rate at which changes may proceed through "natural selection" is an indeterminate quantity. If natural selection be the secondary cause that has determined the development of species, then its speed must have been inversely as the time in which it has operated. If time has been short, natural selection must either have been incompetent for the results, or have worked the faster. We do not know that any clue has been given as to the rapidity with which, in favorable circumstances, changes may proceed in species. Mr. Darwin insists, too strenuously perhaps, upon a very slow rate of variation. By a singular misnomer the school in geology led by Lyell, and of which Darwin's is the complement in natural history, was called uniformitarian, whereas both these distinguished authors emphasize not so much the uniformity of the past as the instability of the present. Time can easily be eliminated when cause and effect are brought into line. It must be admitted that geological measures of time are very indefinite and unsatisfactory.

Without dispute, however, geology opens up an expanse of time through which plants and animals have lived that is ample enough for almost any purpose. The geological succession of the earth's strata extends the present order of things back to a point that is far out of sight. Darwin may with confidence claim one hundred million years, and without much fear of contradiction, five times that period, as a field in which his law may have operated. As near as we can ascertain, we are in the middle of duration, and God has been no more pressed for time in which to do his work in the past than he is to be for the future. God is as prodigal of time as of space, and to appearance has shown himself as little concerned about the fate of the mere forms of life that have in succession inhabited the world, as about the quantity of dirt it has required to make the world; though doubtless, before divine omniscience, every hair of each minutest insect has its place in the general scheme of organic development, and every grain of sand on the surface has been weighed.