254 



APPENDIX B 

 DARWIN AND EVOLUTION BY MUTATION 



I HAVE spoken on pages 43 and 44 of the 

 frequency with which Darwin, between 1860 

 and 1880, was brought back by others to a motive 

 cause of evolution based on * sudden jumps ', or 

 ' monstrosities', on 'large', * extreme', and 'great 

 and sudden ' variations. Such views were con- 

 tinually urged upon him by ' his correspondents, 

 and by reviews and criticisms of his work '. It 

 is I think of interest, in relation to the biological 

 fashions of the day, to show by many examples 

 how firmly he met such suggestions whenever they 

 were made to him. I therefore append the follow- 

 ing quotations from his letters to those on pages 43 

 and 44 and to be found in the Quarterly Review l : 



(1) 1860. ' ... he [Harvey] assumes the permanence of 

 monsters, whereas, monsters are generally sterile, and not 

 often inheritable.' 2 



(2) 1860. ' It would take a good deal more evidence to 

 make me admit that forms have often changed by saltum.' 3 



(3) 1860. 'Although I fully agree that no definition can 

 be drawn between monstrosities and slight variations (such 

 as my theory requires), yet I suspect there is some dis- 

 tinction. Some facts lead me to think that monstrosities 

 supervene generally at an early age ; and after attending to 

 the subject I have great doubts whether species in a state of 

 nature ever become modified by such sudden jumps as 

 would result from the Natural Selection of monstrosities.' 4 



1 July, 1909 ; 10-12, 25, 26. 



2 To Sir Charles Lyell, Feb. 18, I860. Life and Letters, ii. 275. 

 8 To Sir Joseph Hooker, Feb., I860. Ibid., 274. 



4 To Maxwell Masters, April 13, I860. More Letters, i. 147, 148. 



