This essay was published in the Annals and Magazine of Natural History in September 1855. It attracted much attention from Lyell and Darwin and later from Huxley. One important result of it was that Darwin and Wallace entered into friendly correspondence. But although Darwin in his letters to Wallace informed him that he had been engaged for a long time in collecting facts which bore on the question of the origin of species, he gave no hint of the theory of natural selection he had conceived seventeen years before—indeed his friends Lyell and Hooker appear at that time to have been the only persons, outside his family circle, whom he had taken into his confidence.
In the spring of 1858, Wallace was at Ternate in the island of Celebes, where he lay sick with fever, and as his thoughts wandered to the ever-present problem of species, there suddenly recurred to his memory the writings of Malthus, which he had read twelve years before. Then and there, 'in a sudden flash of insight' the idea of natural selection presented itself to his mind, and after a few hours' thought the chief points were written down, and within a week the matter was 'copied on thin letter-paper' and sent to Darwin by the next post, with a letter to the following effect[113]. Wallace stated that the idea seemed new to himself and he asked Darwin, if he also thought it new, to show it to Lyell, who had taken so much interest in his former paper. Little did Wallace think, in the absence of all knowledge on his part of Darwin's own conclusions, what stir would be made by his paper when it arrived in England!
Wallace's essay was entitled On the Tendency of Varieties to depart indefinitely from the Original Type, and it is a singularly lucid and striking presentment, in small compass, of the theory of Natural Selection.
Had these two men been of less noble and generous nature, the history of science might have been dishonoured by a painful discussion on a question of priority. Fortunately we are not called upon for anything like a judicial investigation of rival claims; for Darwin as soon as he read the essay saw that—as Lyell had often warned him might be the case—he was completely forestalled in the publication of his theory. The letter and paper arrived at a sad time for Darwin—he was at the moment very ill, there was 'scarlet fever raging in his family, to which an infant son had succumbed on the previous day, and a daughter was ill with diphtheria[114].' Darwin at once wrote hurriedly to Lyell enclosing the essay and saying:
'I never saw a more striking coincidence; if Wallace had my MS. sketch written out in 1842, he could not have made a better short abstract! Even his terms now stand as heads of my chapters. Please return me the MS., which he does not say he wishes me to publish, but I shall, of course, at once write and offer to send to any journal. So all my originality, whatever it may amount to, will be smashed, though my book, if it ever have any value, will not be deteriorated, as all the labour consists in the application of the theory. I hope you will approve of Wallace's sketch, that I may tell him what to say[115].'
And Wallace—what was the line taken by him in the unfortunate complication that had thus arisen? From the very first his action was all that is generous and noble. Not only did he, from the first, entirely acquiesce in the course taken by Lyell and Hooker, but, writing in 1870, when the fame of Darwin's work had reached its full height, he said:—
'I have felt all my life and I still feel, the most sincere satisfaction that Mr Darwin had been at work long before me, and that it was not left for me to attempt to write The Origin of Species. I have long since measured my own strength and know well that it would be quite unequal to that task. For abler men than myself may confess, that they have not that untiring patience in accumulating, and that wonderful skill in using, large masses of facts of the most varied kind,—that wide and accurate physiological knowledge,—that acuteness in devising and skill in carrying out experiments,—and that admirable style of composition, at once clear, persuasive and judicial,—qualities which in their harmonious combination mark out Mr Darwin as the man, perhaps of all men now living, best fitted for the great work he has undertaken and accomplished[116].'
And fifty years after the joint publication of the theory of Natural Selection to the Linnean Society he said:
'I was then (as often since) the "young man in a hurry," he' (Darwin) 'the painstaking and patient student, seeking ever the full demonstration of the truth he had discovered, rather than to achieve immediate personal fame[117].'
And when he referred to the respective shares of Darwin and himself to the credit of having brought forward the theory of natural selection, he actually suggests as a fair proportion 'twenty years to one week'—those being the periods each had devoted to the subject[118]!