_, 1864, p. 328.

[43] "Read June, 1864."--A.R.W.

[44] "June 8, 1864."--A.R.W.

[45] "Referring to my broken engagement."--A.R.W.

[46] Paper on the three forms of Lythrum.

[47] Probably the one on the Distribution of Malayan Butterflies, _Linn.
Soc. Trans._, xxv.

[48] E.B. Tylor's "Early History of Mankind," and Lecky's "Rationalism."

[49] "Prehistoric Times."

[50] The note speaks of the "characteristic unselfishness" with which
Wallace ascribed the theory of Natural Selection to Darwin.

[51] "Fuer Darwin."

[52] "On the Pigeons of the Malay Archipelago," _Ibis_, October, 1865.
Wallace points out (p. 366) that "the most striking superabundance of
pigeons, as well as of parrots, is confined to the Australo-Malayan
sub-regions in which ... the forest-haunting and fruit-eating mammals,
such as monkeys and squirrels, are totally absent." He points out also
that monkeys are "exceedingly destructive to eggs and young
birds."--Note, "More Letters," i. 265.

[53] "The Geographical Distribution and Variability of the Malayan
Papilionidae," _Linn. Soc. Trans._, xxv.

[54] The passage referred to in this letter as needing farther
explanation is the following: "The last six cases of mimicry are
especially instructive, because they seem to indicate one of the
processes by which dimorphic forms have been produced. When, as in these
cases, one sex differs much from the other, and varies greatly itself,
it may be that individual variations will occasionally occur, having a
distant resemblance to groups which are the objects of mimicry, and
which it is therefore advantageous to resemble. Such a variety will have
a better chance of preservation; the individuals possessing it will be
multiplied; and their accidental likeness to the favoured group will be
rendered permanent by hereditary transmission, and each successive
variation which increases the resemblance being preserved, and all
variation departing from the favoured type having less chance of
preservation, there will in time result those singular cases of two or
more isolated and fixed forms bound together by that intimate
relationship which constitutes them the sexes of a single species. The
reason why the females are more subject to this kind of modification
than the males is probably that their slower flight when laden with
eggs, and their exposure to attack while in the act of depositing their
eggs upon leaves, render it especially advantageous for them to