" The 'Vestiges of Creation' appeared in 1844. In the tenth and much improved edition (1853) the anonymous author [Robert Chambers] says (p. 155): ---'The proposition determined on after much consideration is, that the several series of animated beings, from the simplest and oldest up to the highest and most recent, are, under the providence of God, the results, first, of an impulse {teleologic] which has been imparted to the forms of life, advancing them, in definite times, by generation, through grades of organisation terminating in the highest dicotyledons and vertebrata, these grades being few in number, and generally marked by intervals of organic character, which we find to be a practical difficulty in ascertaining affinities;
second, of another impulse [teleonomic] connected with the vital forces, tending, in the course of generations, to modify organic structures in accordance with external circumstances, as food, the nature of the habitat, and the meteoric [n.b.] agencies, these being the 'adaptations' of the natural theologian." The author apparently believes that organisation progresses by sudden [quantum] leaps, but the effects produced by the conditions of life are gradual. "

― Charles Darwin , The Origin of Species