, the same truth of
evolution by natural selection had been revealed. Among the proofs that
scientific study does no injury to the more delicate shades of sentiment
is the well-known story of this letter. With it Wallace sent Darwin a
memoir, asking him to present it to the Linnaean Society: on examining
it, Darwin found that Wallace had independently arrived at conclusions
similar to his own--possibly had deprived him of fame; but Darwin was
loyal to his friend, and his friend remained ever loyal to him. He
publicly presented the paper from Wallace, with his own conclusions; and
the date of this presentation--July 1, 1858--separates two epochs in the
history, not merely of natural science, but of human thought.

In the following year, 1859, came the first instalment of his work in
its fuller development--his book on The Origin of Species. In this
book one at least of the main secrets at the heart of the evolutionary
process, which had baffled the long line of investigators and
philosophers from the days of Aristotle, was more broadly revealed. The
effective mechanism of evolution was shown at work in three ascertained
facts: in the struggle for existence among organized beings; in the
survival of the fittest; and in heredity. These facts were presented
with such minute research, wide observation, patient collation,
transparent honesty, and judicial fairness, that they at once commanded
the world's attention. It was the outcome of thirty years' work and
thought by a worker and thinker of genius, but it was yet more than
that--it was the outcome, also, of the work and thought of another man
of genius fifty years before. The book of Malthus on the Principle
of Population, mainly founded on the fact that animals increase in a
geometrical ratio, and therefore, if unchecked, must encumber the earth,
had been generally forgotten, and was only recalled with a sneer. But
the genius of Darwin recognised in it a deeper meaning, and now the
thought of Malthus was joined to the new current. Meditating upon it in
connection with his own observations of the luxuriance of Nature, Darwin
had arrived at his doctrine of natural selection and survival of the
fittest.

As the great dogmatic barrier between the old and new views of the
universe was broken down, the flood of new thought pouring over the
world stimulated and nourished strong growths in every field of research
and reasoning: edition after edition of the book was called for; i