All organisms die; but those better suited to a particular surrounding condition have a greater chance of survival than those less suited. (This dreadfully self-evident truth was solemnly set down in an academic formula: it was called “Survival of the Fittest,” or, more clumsily, “Survival of the Fitter”!) Bit by bit, therefore, through the mechanical process of the slightly less fit specimens dying off more rapidly, and leaving presumably less progeny, while a small number of slightly more fit lived longer and presumably left more progeny inheriting their advantages, the type of animal could be, and was, by the blind action of matter and with no necessity for its own or any other will, and with no design in the process at all, adapted to the changing condition. Since conditions are always changing, organic types (i.e. living things, vegetable and animal) were perpetually conforming to their environment by this process of “Survival of the Fittest,” wherein a _mechanical_ process _inevitably_ and _blindly_ picked out—_selected_—(whence the term “Natural Selection”) those who were to survive and form a new type. In this fashion all organic things came to be what they are at any particular moment _and also to change perpetually into new things_. This doctrine of Natural Selection was thus made to explain the diversity and the unity of the living world. Let us see how some simple organism, living on the tidal belt of the sea-shore (between high and low water-mark), and able both to exist in the air and under water will, according to the doctrine of Natural Selection, differentiate out and produce a land animal. Out of a million of these organisms there are, perhaps, ten thousand in which you can discover some slight superiority, present in varying degrees among them, for standing a long dry spell. There are another ten thousand who show in varying degrees some tiny, almost imperceptible, superiority of standing a long spell without air under water. Raising of the land or the set of winds gives a season of abnormally low high tides. The animals just on the upper edge of the tidal belt die out for lack of their regular tidal supply of water, except some few who can, having the slight differential advantage apparent among them, stand the strain of living so long in the air. The progeny of these, again, will tend to survive according to the degree in which they can stand the lack of water about them. The less fit for air-life are gradually sifted out by this natural process; the more fit for air-life survive.