I PROLEGOMENA. 7 



yet gone, it tends, with constantly increasing 

 emphasis, to the belief that, not merely the 

 world of plants, but that of animals; not merely 

 living things, but the whole fabric of the earth; 

 not merely our planet, but the whole solar 

 system; not merely our star and its satellites, 

 but the millions of similar bodies which bear 

 witness to the order which pervades boundless 

 space, and has endured through boundless time; 

 are all working out their predestined courses of 

 evolution. 



With none of these have I anything to do, at 

 present, except with that exhibited by the forms 

 of life which tenant the earth. All plants and 

 animals exhibit the tendency to vary, the causes 

 of which have yet to be ascertained; it is the 

 tendency of the conditions of life, at any given 

 time, while favouring the existence of the varia- 

 tions best adapted to them, to oppose that of the 

 rest and thus to exercise selection; and all 

 living things tend to multiply without limit, 

 while the means of support are limited; the 

 obvious cause of which is the production of 

 offspring more numerous than their progenitors, 

 but with equal expectation of life in the actuarial 

 sense. Without the first tendency there could 

 be no evolution. Without the second, there 

 would be no good reason why one variation should 

 disappear and another take its place; that is to 

 say there would be no selection. Without the 



