e famous number of the
"Linnean Journal" on a certain evening. "I sat up late that night to
read it; and never shall I forget the impression it made upon me. Herein
was contained a perfectly simple solution of all the difficulties which
had been troubling me for months past... I went to bed satisfied that a
solution had been found.")

Why, then, was it, that Darwin succeeded where the rest had failed?
The cause of that success was two-fold. First, and obviously, in the
principle of Natural Selection he had a suggestion which would work. It
might not go the whole way, but it was true as far as it went. Evolution
could thus in great measure be fairly represented as a consequence of
demonstrable processes. Darwin seldom endangers the mechanism he devised
by putting on it strains much greater than it can bear. He at least was
under no illusion as to the omnipotence of Selection; and he introduces
none of the forced pleading which in recent years has threatened to
discredit that principle.

For example, in the latest text of the "Origin" ("Origin", (6th edition
(1882), page 421.)) we find him saying:

"But as my conclusions have lately been much misrepresented, and it has
been stated that I attribute the modification of species exclusively
to natural selection, I may be permitted to remark that in the first
edition of this work, and subsequently, I placed in a most conspicuous
position--namely, at the close of the Introduction--the following words:
'I am convinced that natural selection has been the main but not the
exclusive means of modification.'"

But apart from the invention of this reasonable hypothesis, which may
well, as Huxley estimated, "be the guide of biological and psychological
speculation for the next three or four generations," Darwin made a more
significant and imperishable contribution. Not for a few generations,
but through all ages he should be remembered as the first who showed
clearly that the problems of Heredity and Variation are soluble by
observation, and laid down the course by which we must proceed to
their solution. (Whatever be our estimate of the importance of Natural
Selection, in this we all agree. Samuel Butler, the most brilliant, and
by far the most interesting of Darwin's opponents--whose works are at
length emerging from oblivion--in his Preface (1882) to the 2nd edition
of "Evolution, Old and New", repeats his earlier expression of homage to
one whom he had come to regard as an enem