his the only recognition which reached
him in his remote solitude was a remark in an approving letter from
Darwin (_see_ p. 129).

As Wallace wrote nothing further of importance until the second essay
which more fully disclosed his view of the origin of species, we will
now briefly trace the growth of the theory of Natural Selection up to
1858, as it came to Darwin.

It is well known that during Darwin's voyage in the _Beagle_ he was
deeply impressed by discovering extinct armadillo-like fossil forms in
South America, the home of armadilloes, and by observing the
relationship of the plants and animals of each island in the Galapagos
group to those of the other islands and of South America, the nearest
continent. These facts suggested evolution, and without evolution
appeared to be meaningless.

Evolution and its motive cause were the problems which "haunted" him for
the next twenty years. The first step towards a possible solution was
the "opening of a notebook for facts in relation to the origin of
species" in 1837, two years before the publication of his Journal. From
the very commencement of his literary and scientific work, a rule
rigidly adhered to was that of interspersing his main line of thought
and research by reading books touching on widely diverging subjects; and
it was thus, no doubt, that during October, 1838, he read "for
amusement" Malthus's "Essay on Population"; not, as he himself affirms,
with any definite idea as to its intimate bearing on the subject so near
his heart. But the immediate result was that the idea of Natural
Selection at once arose in his mind, and, in his own words, he "had a
theory by which to work."

In May and June, 1842, during a visit to Maer and Shrewsbury, he wrote
his first "pencil sketch of Species theory," but not until two years
later (1844) did he venture to enlarge this to one of 230 folio pages,
"a wonderfully complete presentation of the arguments familiar to us in
the 'Origin.'"[19]

Already, in addition to the mass of facts collected, Darwin was busy
with some of the experiments which he described in a letter to Sir
Joseph Hooker (in 1855) as affording the latter a "good right to sneer,
for they are so _absurd_, even in _my_ opinion, that I dare not tell
you." While a sentence in another letter (dated 1849) throws a sidelight
on all this preparatory work: "In your letter you wonder what
'ornamental poultry' has to do with barnacles; but do not flatter
yourself