give only the general conclusions at which I have arrived, with a few
facts in illustration, but which, I hope, in most cases will suffice.
No one can feel more sensible than I do of the necessity of hereafter
publishing in detail all the facts, with references, on which my
conclusions have been grounded; and I hope in a future work to do
this. For I am well aware that scarcely a single point is discussed in
this volume on which facts cannot be adduced, often apparently leading
to conclusions directly opposite to those at which I have arrived. A
fair result can be obtained only by fully stating and balancing the
facts and arguments on both sides of each question; and this cannot
possibly be here done.

I much regret that want of space prevents my having the satisfaction
of acknowledging the generous assistance which I have received from
very many naturalists, some of them personally unknown to me. I
cannot, however, let this opportunity pass without expressing my deep
obligations to Dr. Hooker, who for the last fifteen years has aided me
in every possible way by his large stores of knowledge and his
excellent judgment.

In considering the Origin of Species, it is quite conceivable that a
naturalist, reflecting on the mutual affinities of organic beings, on
their embryological relations, their geographical distribution,
geological succession, and other such facts, might come to the
conclusion that each species had not been independently created, but
had descended, like varieties, from other species. Nevertheless, such
a conclusion, even if well founded, would be unsatisfactory, until it
could be shown how the innumerable species inhabiting this world have
been modified, so as to acquire that perfection of structure and
coadaptation which most justly excites our admiration. Naturalists