166 FOUNDATIONS OF THE ORIGIN OF SPECIES. [Oh. IX. 



only on the " supposition that species gradually become modi- 

 fied." He goes on to say that the subject " haunted him " ; and 

 I think it is especially worthy of note that this " haunting," — 

 this unsatisfied dwelling on the subject was connected with the 

 desire to explain how species can be modified. It was charac- 

 teristic of him to feel, as he did, that it was " almost useless " 

 to endeavour to prove the general truth of evolution, unless 

 the cause of change could be discovered. I think that through- 

 out his life the questions 1 and 2 were intimately, — perhaps 

 unduly so, connected in his mind. It will be shown, however, 

 that after the publication of the Origin, when his views were 

 being weighed in the balance of scientific opinion, it was to 

 the acceptance of Evolution not of Natural Selection that he 

 attached importance. 



An interesting letter (Feb. 24, 1877) to Dr. Otto Zacharias,* 

 gives the same impression as the Autobiography : — 



" When I was on board the Beagle I believed in the perma- 

 nence of species, but as far as I can remember, vague doubts 

 occasionally flitted across my mind. On my return home in the 

 autumn of 1836, 1 immediately began to prepare my Journal 

 for publication, and then saw how many facts indicated the 

 common descent of species, so that in July, 1837, I opened a 

 note-book to record any facts which might bear on the question. 

 But I did not become convinced that species were mutable 

 until, I think, two or three years had elapsed." 



Two years bring us to 1839, at which date the idea of 

 natural selection had already occurred to him — a fact which 

 agrees with what has been said above. How far the idea that 

 evolution is conceivable came to him from earlier writers it 

 is not possible to say. He has recorded in the Autobiography 

 (p. 38) the " silent astonishment with which, about the year 

 1825, he heard Grant expound the Lamarckian philosophy." 

 He goes on : — 



" I had previously read the Zoonomia of my grandfather, in 

 which similar views are maintained, but without producing 

 any effect on me. Nevertheless, it is probable that the hearing 

 rather early in life such views maintained and praised, may 

 have favoured my upholding them under a different form in 

 my Origin of Species. At this time I admired greatly the 

 Zoonomia ; but on reading it a second time after an interval of 

 ten or fifteen years, I was much disappointed ; the proportion 

 of speculation being so large to the facts given." 



Mr. Huxley has well said {Obituary Notice, p. ii.) : " Erasmus 



* This letter was unaccountably overlooked in preparing the Life awj 

 Letters for publication. 



