This chapter explores a few preliminary remarks, to show how the Struggle for Existence bears on Natural Selection. But Natural Selection, as we shall hereafter, is a power incessantly ready for action, and is as immeasurably superior to man's feeble efforts, as the works of nature are to those of art. There is no exception to the rule that every organic being naturally increases at so high a rate, that if not destroyed, the earth would soon be covered by the progeny of a single pair. In such cases the geometrical ratio of increase, the result of which never fails to be surprising, simply explains the extraordinarily rapid increase and wide diffusion of naturalized productions in their new homes. What checks the natural tendency of each species to increase in number is most obscure. Look at the most vigorous species; by as much as it swarms in numbers, by so much will its tendency to increase be still further increased.