111], there was among naturalists during the second quarter of
the nineteenth century a feeling of dissatisfaction with respect to
current ideas concerning the origin of species, accompanied in many
cases with one of expectation that a solution might soon be found.
Others, however, despairingly regarded it as 'the mystery of mysteries'
for which it was hopeless to attempt to find a key. There was, however,
one man, who simultaneously with Darwin was meditating earnestly on the
problem and who eventually reached the same goal.

Alfred Russel Wallace was born thirteen years after Darwin, and a
quarter of a century after Lyell. He did not possess the moderate income
that permits of entire devotion to scientific research--an advantage,
the importance of which in their own cases, both Lyell and Darwin were
always so ready to acknowledge. Wallace, after working for a time as a
land-surveyor and then as a teacher, at the age of 26 set off with
another naturalist, H. W. Bates, on a collecting tour in South
America--hoping by the sale of specimens to cover the expenses of
travel. Like Lyell and Darwin, he was an enthusiastic entomologist, and
had conceived the same passion for travel. He had, as we have already
seen, been deeply impressed by reading the _Principles of Geology_, and
after spending four years in South America undertook a second collecting
tour, which lasted twice that time, in the Malay Archipelago.

[Illustration: Alfred R. Wallace]

Before leaving England in 1848, Wallace had read and been impressed by
reading the _Vestiges of Creation_, and there can be no doubt that from
that period the question of evolution was always more or less distinctly
present in his mind. While in Sarawak in the wet season, he tells us, 'I
was quite alone with one Malay boy as cook, and during the evenings and
wet days I had nothing to do but to look over my books and ponder over
the problem which was rarely absent from my thoughts.' He goes on to
say that by 'combining the ideas he had derived from his books that
treated of the distribution of plants and animals with those he obtained
from the great work of Lyell' he thought 'some valuable conclusions
might be reached[112].' Thus originated the very remarkable paper, _On
the Law which has regulated the Introduction of New Species_, the main
conclusion of which was as follows: 'Every species has come into
existence coincident both in space and time with a pre-existing closely
allied