Natural Selection almost inevitably causes much Extinction of the less improved forms of life and induces what I have called Divergence of Character.

There is grandeur in this view of life... [in which] endless forms most beautiful and most wonderful have been, and are being, evolved.

From the first dawn of life, all organic beings are found to resemble each other in descending degrees, so that they can be classed in groups under groups. This classification is evidently not arbitrary like the grouping of stars in constellations.

We cannot fathom the marvelous complexity of an organic being; but on the hypothesis here advanced this complexity is much increased. Each living creature must be looked at as a microcosm--a little universe, formed of a host of self-propagating organisms, inconceivably minute and as numerous as the stars in heaven.

If the country were open on its borders, new forms would certainly immigrate, and this would also seriously disturb the relations of some of the former inhabitants. Let it be remembered how powerful the influence of a single introduced tree or mammal has been shown to be.

Sexual selection acts in a less rigorous manner than natural selection. The latter produces its effects by the life or death at all ages of the more or less successful individuals.