November 2, 191 1] 



NATURE 



II 



with him from England. In his dedication of the 

 second edition of his "Journal," Darwin wrote, "The 

 chief part of whatever scientific merit this journal 

 .and the other works of the author may possess has 

 been derived from studying the well-known and admir- 

 able 'Principles of Geology. '"^^ 



In a letter to his friend, at the same time, Darwin 

 •clearly explains the nature of his indebtedness to the 

 "Principles." He says, " Those authors . . . who, like 

 you, educate people's minds as well as teach them 

 special facts, can never, I should think, have full 

 justice done them except by posterity, for the mind 

 thus insensibly improved can hardly perceive its own 

 upward ascent." '^^ And shortly before this he had 

 written to Leonard Horner, " I have always thought 

 that the great merit of the Principles was that it 

 altered the whole tone of one's mind, and therefore 

 that, when seeing a thing never seen by Lyell, one 

 yet saw it partially thro,ugh his eyes." -' 



It has been pointed out, both by Huxley and 

 Haeckel, that when Lyell had completed the first 

 volume of his great work he had arrived at the 

 logical conclusion that the same principle of con- 

 tinuity or uniformity which he had demonstrated for 

 the inorganic world must apply also to organic nature 

 and even to man. This Is clearly shown in the corre- 

 spondence that has been published,-^ which also makes 

 it manifest that some among Lyell 's contemporaries 

 who thought deeply on the subject could not avoid 

 the same conclusion. Sedgwick clearly perceived this, 

 and it moved him to rage and to making wild charges 

 of "infidelity." Whewell saw it too, and shrank 

 from accepting Lyell's doctrines because he could find 

 no border-line between what he called " uniformi- 

 tarianism " and evolution ; but Herschel appears, at 

 the time, to have been ready to go as far as Lyell 

 himself. And the young naturalist on board the 

 Beagle, did he begin to perceive, however dimly, 

 "through Lyell's eyes" that evolution could not stop 

 with the inorganic world? We have no evidence on 

 this point; we can only conjecture it as possible. 



This much, however. Is certain, that Darwin, after 

 completing his excavations at Punta Alta, returned 

 to Monte Video, and among the articles sent from 

 home which were awaiting him there, found the 

 second volume of the "Principles," and wrote In it 

 "Monte Video, November. 1832." The volume treats 

 of the "Changes in the Organic World now in Pro- 

 gress." It is true that Lyell had been so far Influ- 

 enced by his friend Cuvler that he commenced the 

 book with a very trenchant criticism of the theory of 

 Lamarck, but he then goes on to discuss a number of 

 problems^ of extreme Interest and importance to the 

 evolutionist — the limits between species and varieties ; 

 variation under domestication and In nature; the 

 effects of crossing and the characters of hvbrlds; the 

 geographical distribution of plants and animals, and 

 I the^ agencies by which It has been brought about; 

 extinction and the appearance of new iforms ; the 

 I struggle for existence ; the origin of Instincts ; and the 

 i bearing of all these and similar questions on the 

 ; interpretation of the geological history of past times. 

 Great as was the Influence of the first volume on the 

 mind of Darwin with regard to geological questions, I 

 think no one can now read this second volume with- 

 out realising that, in respect to biological problems, it 

 must have exercised at least an equally profound 

 effect upon him. It could be easllv shown from the 

 "Journal " that all these problems were, from this 

 time forth, ever in Darwin's thoughts, and as new 



NO. 2192, VOL. 88] 



observations were made by him, he delighted to 

 think, as shown by his letters, that they would •"in- 

 terest Mr. Lyell," who was at that time not person- 

 ally known to him. 



I am very far from suggesting that the collection 

 of the fossil bones at Punta Alta and the perusal of 

 Lyell's second volume made Darwin an evolutionist. 

 On the contrary, I fully admit, with Dr. Francis 

 Darwin, that it was the series of wonderful relations 

 revealed to him towards the end of the voyage, by his 

 study of the faunas of the Galapagos Islands, that had 

 the preponderating influence in moulding Darwin's 

 views ; and I am convinced that anything like a 

 definite formulation of those views did not take place 

 until after his return to England. It was then that, 

 by the re-examination of his collections and the revi- 

 sion of the observations in his notebooks and journal, 

 he was led to bring into close array the various facts 

 and reflections bearing on "the species question," and 

 thus the scattered gleams of light on the subject 

 which he had from time to time caught were first 

 brought to a focus in his mind ; nevertheless. It is 

 true that the first of those gleams were those that 

 came to him at Punta Alta and during the perusal 

 of the " Principles." 



There is a passage in one of Darwin's letters to 

 Bentham the significance of which, I think, has been 

 somewhat overlooked. Speaking of the fluctuations 

 of opinion on the question of the immutability of 

 species, he says : — 



"I, for one, can conscientiously declare that I never 

 feel surprised at anyone sticking to the belief of 

 immutability. ... I remember too well my endless 

 oscillations of doubt and difficulty. It is to me really 

 laughable, when I think of the years which elapsed 

 before I saw what I believe to be the explanation of 

 some parts of the case ; I believe It was fifteen years 

 after I began before I saw the meaning and cause 

 of the divergence of the descendants of any one 

 pair." ^' 



Fifteen years after 1832 would bring us to 1847, a 

 period at which Darwin was fully immersed In the 

 task of " making and unmaking species " among the 

 Cirrlpedes, and in their classification ; and it may well 

 have been the consideration of "one pair" of these 

 that led him first clearly to realise " the meaning and 

 cause of divergence." In his autobiography he wrote. 

 " Long after I had come to Down " (which was In 

 1842) " whilst in my carriage to my joy the solution 

 occurred to me," and " I can remember the very spot 

 in the road." ^^ Although, as Dr. Francis Darwin 

 has shown, '^ his father had come very near to this 

 idea of divergence when he wrote the 1842 sketch,^' 

 and the same is true with regard to the essay of 

 1844,'^ It was clearly after these dates that the full 

 significance of the principle revealed itself to 

 his mind, and that it was the result of 

 pondering on questions of classification is shown 

 by his letter of September, 1857, to Asa Gray, 

 which he communicated to the Linnean Society 

 in 1858. He there wrote : — " Each new variety or 

 species when formed will generally take the place of 

 and so exterminate Its less well-fitted parent. This 

 1 believe to be the origin of the classification or 

 arrangement of all organic beings at all times." '* 



If this reasoning be correct, we obtain the date of 

 a crisis in Darwin's mental development to which 

 he himself attached the greatest importance. How- 

 ever this may be. the letter to Bentham proves what 

 is often overlooked, that Darwin's mind vacillated 



23 " Life and Lette-s," vol. iii., p. 96. "* //'id., vol. i., p. 84. 



31 " Foundations'of the Oricin of Species," p. xxiv. '^ TMd., p. 37. 



^•' Ihid., pp. 208-ti. See also " Origin of Species " (1859), chap. xiii. 

 •'■* " Linnean Society-Darwin-Waliace Celebration," p. 97. 



