Canon Tristram then points out the manner in which he imagines that one of the crested larks of the desert has been produced by the survival of the lightest coloured individuals, _Galerida abyssinica_ only differing in this respect from _G. cristata_ of Europe. Short-billed species of the same genus inhabiting hard rocky districts, and long-billed inhabiting loose sandy tracts have, he believes, been produced by the survival in each case of the forms of bill most suited to procure food: “Here are only two causes enumerated which might serve to _create_ as it were a new species from an old one, yet they are perfectly natural causes, and such as, I think, must have occurred, and are possibly occurring still. We know so very little of the causes which in the majority of cases make species rare or common, that there may be hundreds of others at work, some even more powerful than these, which go to perpetuate and eliminate certain forms ‘according to natural means of selection.’ But even these superficial causes appear sufficient to explain the marked features of the Desert races, which frequently approach so very closely the typical form, and yet possess such invariably distinctive characteristics, that naturalists seem agreed to elevate them to the rank of species.” Although the author also declares his belief in the special creation of many species--a view put forward as possible by Darwin in the “Origin”[G]--and also believed in some direct influence of locality, climate, etc., the above quoted passages are a most complete acceptance of natural selection, at the same time affording excellent examples of its operation. CHAPTER XIV. THE PREPARATION OF “THE ORIGIN OF SPECIES” (1858–59). Almost immediately after the Linnean Society meeting, and evidently earlier than September, the time mentioned in his “Autobiography,” Darwin began to prepare a longer and more complete account of his work on evolution and natural selection. This account was at first intended for the Linnean Society, but it was soon found to be too long, and he then decided to publish it as an independent volume. In thus preparing the manuscript for what afterwards became the “Origin of Species,” Darwin tells us (“Autobiography”) he acted under “the strong advice of Lyell and Hooker,” and his letters also show the great interest that they were taking in the work. Darwin seems to have found the “Origin”--or his “Abstract,” as he always calls it--very hard work, and he ends his letter to Wallace (January 25th, 1859) with the words: “I look at my own career as nearly run out. If I can publish my Abstract and perhaps my greater work on the same subject, I shall look at my course as done.”