Linnean Society in 1858 he said, in a passage which I have quoted in
"Unconscious Memory":

"The hypothesis of Lamarck--that progressive changes in species have
been produced by the attempts of the animals to increase the
development of their own organs, and thus modify their structures
and habits--has been repeatedly and easily refuted by all writers on
the subject of varieties and species; . . . but the view here
developed renders such an hypothesis quite unnecessary. . . . The
powerful retractile talons of the falcon and cat tribes have not
been produced or increased by the volition of those animals; . . .
neither did the giraffe acquire its long neck by desiring to reach
the foliage of the more lofty shrubs, and constantly stretching its
neck for this purpose, but because any varieties which occurred
among its antitypes with a longer neck than usual AT ONCE SECURED A
FRESH RANGE OF PASTURE OVER THE SAME GROUND AS THEIR SHORTER-NECKED
COMPANIONS, AND ON THE FIRST SCARCITY OF FOOD WERE THUS ENABLED TO
OUTLIVE THEM" (italics in original). {96a}

"Which occurred" is obviously "which happened to occur, by some
chance or accident entirely unconnected with use and disuse;" and
though the word "accidental" is never used, there can be no doubt
about Mr. Wallace's desire to make the reader catch the fact that
with him accident, and not, as with Erasmus Darwin and Lamarck,
sustained effort, is the main purveyor of the variations whose
accumulation amounts ultimately to specific difference. It is a
pity, however, that instead of contenting himself like a theologian
with saying that his opponent had been refuted over and over again,
he did not refer to any particular and tolerably successful attempt
to refute the theory that modifications in organic structure are