444 MISCELLANEOUS SUBJECTS [Chap. XII 



world he can observe accurately." In a letter to Dr. Dohrn, of Naples, 

 Jan. 4th, 1870, Darwin wrote : " Forgive me for suggesting one caution ; 

 as Demosthenes said, ' Action, action, action,' was the soul of eloquence, 

 so is caution almost the soul of science." 



Letter 778 To J. Burdon Sanderson. 



Down, July 16th, 1875. 

 Some little time ago Mr. Simon l sent me the last Report, 

 and your statements about contagion deeply interested me. 

 By the way, if you see Mr. Simon, and can remember it, 

 will you thank him for me ; I was so busy at the time that 

 I did not write. Having been in correspondence with Paget 

 lately on another subject, I mentioned to him an analogy 

 which has struck me much, now that we know that sheep- 

 pox is fungoid ; and this analogy pleased him. It is that 

 of fairy rings, which are believed to spread from a centre, 

 and when they intersect the intersecting portion dies out, as 

 the mycelium cannot grow where it has grown during previous 

 years. So, again, I have never seen a ring within a ring ; 

 this seems to me a parallel case to a man commonly having 

 the smallpox only once. I imagine that in both cases the 

 mycelium must consume all the matter on which it can subsist. 



Letter 779 To A. Gapitche. 



The following letter was written to the author (under the pseudonym 

 of Gapitche) of a pamphlet entitled Qicelques ?twts sur FEterniti du Corps 

 Humaine (Nice, 1880). Mr. Gapitche's idea was that man might, by 

 perfect adaptation to his surroundings, indefinitely prolong the duration 

 of life. We owe Mr. Darwin's letter to the kindness of Herr Vetter, 

 editor of the well-known journal Kosmos. 



Down, Feb. 24th, 1880. 

 I suppose that no one can prove that death is inevitable, 

 but the evidence in favour of this belief is overwhelmingly 

 strong from the evidence of all other living creatures. I do 

 not believe that it is by any means invariably true that 

 the higher organisms always live longer than the lower ones. 

 Elephants, parrots, ravens, tortoises, and some fish live longer 

 than man. As evolution depends on a long succession of 

 generations, which implies death, it seems to me in the 

 highest degree improbable that man should cease to follow 



1 Now Sir John Simon : he was for many years medical officer of the 

 Privy Council, and in that capacity issued a well-known series of Reports. 



