Now for an analogous process without man. Let our sheep live wild in any country. No human breeder has any interest in them: God does not seem to interfere with them. They live on and on, for thousands of years, generation after generation. Here again, in the wild state, we find the same slight variations in the quality of the wool. One sheep has a thicker coat than another. For thousands of years the fact is without significance. Then occurs a slow change of the environment. The climate becomes colder. Perhaps an ice-age sets in, such as our earth seems to have passed through many times. There are two alternatives. A very hard winter may set in at once and all the sheep perish, because their woolly coat is too thin in all cases. That would mean the extinction of a whole species. But the severe cold may come on gradually. The winters are more trying. So many sheep perish in the first winters; but so many others survive. Which will survive? Naturally, those that happened to have the thicker coats. Those alone live on to the spring, and reproduce. The following year the coat is thicker all round, as the lambs all came from relatively thick-coated parents. The winter decimates them again, and the thickest coated survive once more, and so on. The pressure of external conditions, the “struggle for life,” selects just as man does. Only the best adapted individuals survive and reproduce. The whole earth is a vast field of splendid adaptations. The tree-frogs are green because only green frogs are preserved; all the others are destroyed. The arctic hare is white on the snow, the desert-fox yellow. For a thousand reasons in the course of the earth’s development these backgrounds—white, yellow, green; snow, desert, forest, &c.—have themselves been constantly changing under the action of Lyell’s changes in the crust of the earth. Hence constantly fresh adaptations, with a certain percentage of complete extinctions. In these ceaseless new adaptations we see a picture of an eternal progressive development. Always a finer selection: always better material: natural things always selecting and being selected. Man is superfluous in this world-old, eternal process. And God, too, is superfluous. That was Darwin’s last and decisive thought. Divine action was excluded from the whole province of animal and plant species. It does not matter whether or no the shrewd idea of natural selection solves the whole problem. Why speak of “whole,” when all problems are really unfathomable? He left open the question of the origin of the first slight variations, the first increase in the fineness or thickness of the sheep’s wool, for instance. He left open the question of the inner nature of the process—and a good deal more. But these things did not affect the great issue.