PROLEGOMENA 47 



going on for innumerable ages, appears to me to be a 

 proposition as well established as any in modern history. 

 Paleontology assures us, in addition, that the ancient phil- 

 osophers who, with less reason, held the same doctrine, 

 erred in supposing that the phases formed a cycle, exactly 

 repeating the past, exactly foreshadowing the future, in 

 their rotations. On the contrary, it furnishes us with 

 conclusive reasons for thinking* that, if every link in 

 the ancestry of these humble indigenous plants had been 

 preserved and were accessible to us, the whole would 

 present a converging series of forms of gradually dimin- 

 ishing complexity, until, at some period in the history of 

 the earth, far more remote than any of which organic 

 remains have yet been discovered, they would merge in 

 those low groups among which the boundaries between 

 animal and vegetable life become effaced. 4 



The word "evolution," now generally applied to the 

 cosmic process, has had a singular history, and is used in 

 various senses. 5 Taken in its popular signification it 

 means progressive development, that is, gradual change 

 from a condition of relative uniformity to one of relative 

 complexity; but its connotation has been widened to in- 

 clude the phenomena of retrogressive metamorphosis, 

 that is, of progress from a condition of relative complexity 

 to one of relative uniformity. 



As a natural process, of the same character as the 

 development of a tree from its seed, or of a fowl from 

 its egg, evolution excludes creation and all other kinds of 

 supernatural intervention. As the expression of a fixed 

 order, every stage of which is the effect of causes operat- 

 ing according to definite rules, the conception of evolu- 

 tion no less excludes that of chance. It is very desirable 



4 "On the Border Territory between the Animal and the Vege- 

 table Kingdoms," Essays, vol. viii. p. 162. [T. H. H.] 



5 See "Evolution in Biology," Essays, vol. ii. p. 187. [T. H. H.I 



