The Foundations of the Origin of Species

The sections into which the Essay of 1842 is divided are in the original
merely indicated by a gap in the MS. or by a line drawn across the page.
No titles are given except in the case of § VIII.; and § II. is the only
section which has a number in the original. I might equally well have
made sections of what are now subsections, _e.g. Natural Selection_ p.
7, or _Extermination_ p. 28. But since the present sketch is the germ of
the Essay of 1844, it seemed best to preserve the identity between the
two works, by using such of the author's divisions as correspond to the
chapters of the enlarged version of 1844. The geological discussion with
which Part II begins corresponds to two chapters (IV and V) of the 1844
Essay. I have therefore described it as §§ IV. and V., although I cannot
make sure of its having originally consisted of two sections. With this
exception the ten sections of the Essay of 1842 correspond to the ten
chapters of that of 1844.