ch had appeared in print September,
1855. In reply he says: "To persons who have not thought much on the
subject I fear my paper on the 'Succession of Species' will not appear
so clear as it does to you. That paper is, of course, merely the
announcement of the theory, not its development. I have prepared the
plan and written portions of a work embracing the whole subject, and
have endeavoured to prove in detail what I have as yet only
indicated.... I have been much gratified by a letter from Darwin, in
which he says that he agrees with 'almost every word' of my paper. He
is now preparing his great work on 'Species and Varieties,' for which he
has been preparing materials for twenty years. He may save me the
trouble of writing more on my hypothesis, by proving that there is no
difference in nature between the origin of species and of varieties; or
he may give me trouble by arriving at another conclusion; but, at all
events, his facts will be given for me to work upon. Your collections
and my own will furnish most valuable material to illustrate and prove
the universal application of the hypothesis. The connection between the
succession of affinities and the geographical distribution of a group,
worked out species by species, has never yet been shown as we shall be
able to show it."

"This letter proves," writes Wallace,[22] "that at this time I had not
the least idea of the nature of Darwin's proposed work nor of the
definite conclusions he had arrived at, nor had I myself any
expectations of a complete solution of the great problem to which my
paper was merely the prelude. Yet less than two months later that
solution flashed upon me, and to a large extent marked out a different
line of work from that which I had up to this time anticipated.... In
other parts of this letter I refer to the work I hoped to do myself in
describing, cataloguing, and working out the distribution of my insects.
I had in fact been bitten by the passion for species and their
description, and if neither Darwin nor myself had hit upon 'Natural
Selection,' I might have spent the best years of my life in this
comparatively profitless work. But the new ideas swept all this away."

This letter was finished after his arrival at Ternate, and a few weeks
later he was prostrated by a sharp attack of intermittent fever which
obliged him to take a prolonged rest each day, owing to the exhausting
hot and cold fits which rapidly succeeded one another.

The