I have called Divergence of Character.
In the next chapter I shall discuss the complex and little known laws of
variation and of correlation of growth. In the four succeeding chapters,
the most apparent and gravest difficulties on the theory will be given:
namely, first, the difficulties of transitions, or in understanding how
a simple being or a simple organ can be changed and perfected into a
highly developed being or elaborately constructed organ; secondly
the subject of Instinct, or the mental powers of animals, thirdly,
Hybridism, or the infertility of species and the fertility of varieties
when intercrossed; and fourthly, the imperfection of the Geological
Record. In the next chapter I shall consider the geological succession
of organic beings throughout time; in the eleventh and twelfth, their
geographical distribution throughout space; in the thirteenth, their
classification or mutual affinities, both when mature and in an
embryonic condition. In the last chapter I shall give a brief
recapitulation of the whole work, and a few concluding remarks.

No one ought to feel surprise at much remaining as yet unexplained in
regard to the origin of species and varieties, if he makes due allowance
for our profound ignorance in regard to the mutual relations of all
the beings which live around us. Who can explain why one species ranges
widely and is very numerous, and why another allied species has a narrow
range and is rare? Yet these relations are of the highest importance,
for they determine the present welfare, and, as I believe, the future
success and modification of every inhabitant of this world. Still less
do we know of the mutual relations of the innumerable inhabitants of the
world during the many past geological epochs in its history. 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 exclu