The Trend of Evolutionary Thought. 7 



induced by the direct action of the environment. He knew 

 about the struggle for existence and elimination of the least 

 perfect. He also referred to the formation of new varieties of 

 animals by artificial selection, and showed that similar results 

 might be produced in nature liy migration. 



Erasmus Darwin (1731 — 1802) is the next writer who 

 interests us greatly. He was grandfather of Charles Darwin, and 

 was not less enthusiastic about evolution than his famous grand- 

 son. He wrote much in prose and verse, and in his writings he 

 anticipated Lamarck in teaching that organisms vary because of 

 their doings, and that the results of their exertions are transmitted 

 to their posterity. He did not, like Buffon, lay stress on the 

 direct action of the environment, but rather emphasized the idea 

 that modifications spring from within, as a result of the strivings 

 of the organisms during many generations. Even plants, 

 according to him, make efforts towards certain ends. 



Lamarck (1744 — 1829) came after Erasmus Darwin, and 

 apparently without having read the latter's works, gave expression 

 to the same general ideas on the evolution of animals that had 

 been put forward by Darwin. Rather curiously, he followed 

 BufFon in regard to the evolution of plants, believing that they 

 were evolved by the direct action of the environment. But as 

 regards animals he took the same view as Erasmus Darwin, 

 holding that environment did not act directly to produce modifi- 

 cations, but only indirectly, through the nervous system. The 

 essential cause of new structures was the striving of the animal. 

 A felt want (besoin) led to action, and that to modification. The 

 second great doctrine of the Lamarckian creed was that acquired 

 characters are transmitted to offspring. 



Lamarkism is regarded as vitalistic because of the psychical 

 factor implied in the ivant that gives rise to activity ; but 

 Lamarck was strongly opposed to the old Aristotelian idea of a 

 perfecting tendency in nature. He rather ascribed the variety 

 and perfect adaptation of animals to the fact that the species, 

 while spreading in all the habitable regions of the globe, have — 



