But at that time I overlooked one problem of great importance; and it is astonishing to me, except on the principle of Columbus and his egg, how I could have overlooked it and its solution.  This problem is the tendency in organic beings descended from the same stock to diverge in character as they become modified.  That they have diverged greatly is obvious from the manner in which species of all kinds can be classed under genera, genera under families, families under sub-orders and so on; and I can remember the very spot in the road, while riding in my carriage, that, to my joy, the solution occurred to me; and this was long after I had come to Down.  The solution, as I believe, is that the modified offspring of all dominant and increasing forms tend to become adapted to many and highly diversified places in the economy of nature.

Early in 1856 Lyell advised me to write out my views fully, and I began at once to do so on a scale three or four times as extensive as that which was afterward followed in my Origin of Species; yet it was only an abstract of the materials which I had collected, and I got through about half the work on this scale.  But my plans were overthrown, for early in the summer of 1858 Alfred Russel Wallace, who was then in the Malay Archipelago, sent me an essay On the Tendency of Varieties to Depart Indefinitely from the Original Type, and this essay contained exactly the same theory as mine.  Mr. Wallace expressed the wish that if I thought well of his essay, I should send it to Lyell for perusal.

The circumstances under which I consented, at the request of Lyell and Hooker, to allow of an abstract from my manuscript, together with a letter to Asa Gray, dated September 5, 1857, to be published at the same time with Wallace’s essay, are given in the Journal of the Proceedings of the Linnean Society, 1858.  I was at first very unwilling to consent, as I thought Mr. Wallace might consider my doing so unjustifiable, for I did not then know how generous and noble was his disposition.  Neither the extract from my manuscript nor the letter to Gray had been intended for publication, and they were badly written.  Mr. Wallace’s essay, on the other hand, was admirably expressed and quite clear.  Nevertheless, our joint productions excited very little attention, and the only published notice of them which I can remember was by Professor Haughton, of Dublin, whose verdict was that all that was new in them was false, and what was true was old.  This shows how necessary it is that any new view should be explained at considerable length in order to arouse public attention.

In September, 1858, I set to work by the strong advice of Lyell and Hooker to prepare a volume on the transmutation of species, but was often interrupted by ill-health and short visits to Doctor Lane’s delightful hydropathic establishment at Moor Park.  I abstracted the manuscript begun on a much larger scale in 1856, and completed the volume on the same reduced scale.  It cost me thirteen months and ten days’ hard labor.  It was published under the title of the Origin of Species, in November, 1859.  Though considerably added to and corrected in the later editions, it has remained substantially the same book.