forth the same idea of
selection. One was written by Charles Darwin in Kent, the other by
Alfred Wallace in Ternate, in the Malay Archipelago. It was a splendid
proof of the magnanimity of these two investigators, that they thus in
all friendliness and without envy, united in laying their ideas
before a scientific tribunal: their names will always shine side by
side as two of the brightest stars in the scientific sky.

The idea of selection set forth by the two naturalists was at the time
absolutely new, but it was also so simple that Huxley could say of it
later, "How extremely stupid not to have thought of that." As Darwin
was led to the general doctrine of descent, not through the labours of
his predecessors in the early years of the century, but by his own
observations, so it was in regard to the principle of selection. He
was struck by the innumerable cases of adaptation, as, for instance,
that of the woodpeckers and tree-frogs to climbing, or the hooks and
feather-like appendages of seeds, which aid in the distribution of
plants, and he said to himself that an explanation of adaptations was
the first thing to be sought for in attempting to formulate a theory
of evolution.

But since adaptations point to _changes_ which have been undergone by
the ancestral forms of existing species, it is necessary, first of
all, to inquire how far species in general are _variable_. Thus
Darwin's attention was directed in the first place to the phenomenon
of variability, and the use man has made of this, from very early
times, in the breeding of his domesticated animals and cultivated
plants. He inquired carefully how breeders set to work, when they
wished to modify the structure and appearance of a species to their
own ends, and it was soon clear to him that _selection for breeding
purposes_ played the chief part.

But how was it possible that such processes should occur in free
nature? Who is here the breeder, making the selection, choosing out
one individual to bring forth offspring and rejecting others? That was
the problem that for a long time remained a riddle to him.

Darwin himself relates how illumination suddenly came to him. He had
been reading, for his own pleasure, Malthus' book on Population, and,
as he had long known from numerous observations, that every species
gives rise to many more descendants than ever attain to maturity, and
that, therefore, the greater number of the descendants of a species
perish witho