256 APPENDIX C 



first of them ; the assumption that he had made 

 Natural Selection the sole motive cause of evolu- 

 tion forms the second : 



' I am sorry to find that Sir Wyville Thomson does not 

 understand the principle of Natural Selection, as explained 

 by Mr. Wallace and myself. If he had done so, he could 

 not have written the following sentence in the Introduction 

 to the Voyage of the Challenger : " The character of the 

 abyssal fauna refuses to give the least support to the theory 

 which refers the evolution of species to extreme variation 

 guided only by Natural Selection." ' ' 



APPENDIX C 



WORK ESSENTIAL FOR DARWIN'S 

 HEALTH AND COMFORT 



THE alteration in tastes and interests which 

 Darwin described in himself has been wrongly 

 interpreted. The errors have been widely spread 

 and are repeated by able and influential writers 

 even at the present day. 2 It is important in 

 justice to scientific men as a body and especially 

 to Darwin himself to show by repeated evidence 

 the true cause of the changes set down in the 

 autobiography. I have therefore added a number 

 of quotations from Darwin's letters to the evi- 

 dence brought forward on pages 59-66 and 

 yielded by the correspondence with Roland Trimen 

 on pages 218 to 246. The two passages written 

 in 1859 refer to the preparation of the Origin 

 of Species : 



1 More Letters, i. 388. See Nature, Nov. 11, 1880, p. 32. 

 * See pp. 79-83. 



