THE DOGMA OF EVOLUTION 



vourable changes, he assumed, would become fixed 

 traits constantly increasing until a new species was 

 formed. He also took for granted, as a fact of nature, 

 although we cannot give any satisfactory cause, that 

 all progeny vary in slight particulars from their an- 

 cestors. 



Darwin hesitated for a long time as to what name 

 to apply to this cause of evolution. He favoured the 

 striking phrase "the survival of the fittest," with 

 which Spencer had caught the popular fancy, as being 

 in the closest agreement to his own views of evolution, 

 but finally decided on the title of "natural selection" 

 as best expressing the idea that nature selects for 

 preservation every least change of structure or habit 

 which tends to the advantage of the species. 



With his ideas fixed in this purely a priori or de- 

 ductive fashion, Darwin, now settled at Down, de- 

 termined to devote his life to collecting data for and 

 against his doctrine and, in spite of the temptation 

 to favour those things which confirm one's precon- 

 ceived ideas and to explain away those which are an- 

 tithetical, he was extraordinarily anxious to record 

 all facts which were unfavourable. At intervals, he 

 carried on extensive and most important research 

 work on other problems, although their subject-mat- 

 ter usually had a somewhat close connection with the 

 mutation of species ; the only systematic work in zo- 

 ology which he undertook was a laborious and im- 



: 1883 



