This is what the guy wrote in his introduction to ‘On the Origins of Species’ in 1859:

‘Although much remains obscure, and will long remain obscure, I can entertain no doubt, after the most deliberate study and dispassionate judgment of which I am capable, that the view which most naturalists entertain, and which I formerly entertained—namely, that each species has been independently created—is erroneous. I am fully convinced that species are not immutable; but that those belonging to what are called the same genera are lineal descendants of some other and generally extinct species, in the same manner as the acknowledged varieties of any one species are the descendants of that species. Furthermore, I am convinced that Natural Selection has been the main but not exclusive means of modification.’

got that from this new site which published online everything Darwin has written:

http://darwin-online.org.uk/content/frameset?itemID=F373&viewtype=side&pageseq=1

Good idea to put this online!