orous bird. On the other hand, every gaily coloured,
spotted or banded species, which never conceal themselves, and all spiny
and hairy kinds, are _invariably rejected_, either without or after
trial. He has also come to the curious and rather unexpected conclusion,
that hairy and spiny caterpillars are not protected by their hairs, but
by their nauseous taste, the hairs being merely an external mark of
their uneatableness, like the gay colours of others. He deduces this
from two kinds of facts: (1) that very young caterpillars before the
hairs are developed are equally rejected, and (2) that in many cases the
smooth pupae and even the perfect insects of the same species are equally
rejected.

His facts, it is true, are at present not very numerous, but they all
point one way. They seem to me to lend an immense support to my view of
the great importance of protection in determining colour, for it has not
only prevented the eatable species from ever acquiring bright colours,
spots, or markings injurious to them, but it has also conferred on all
the nauseous species distinguishing marks to render their uneatableness
more protective to them than it would otherwise be. When you have read
my book I shall be glad of any hints for corrections if it comes to
another edition. I was horrified myself by coming accidentally on
several verbal inelegancies after all my trouble in correcting, and I
have no doubt there are many more important errors.--Believe me, dear
Darwin, yours very truly,

ALFRED R. WALLACE.

* * * * *

_Down, Bromley, Kent, S.E. March 22, 1869._

My dear Wallace,--I have finished your book.[78] It seems to me
excellent, and at the same time most pleasant to read. That you ever
returned alive is wonderful after all your risks from illness and sea
voyages, especially that most interesting one to Waigiou and back. Of
all the impressions which I have received from your book, the strongest
is that your perseverance in the cause of science was heroic. Your
descriptions of catching the splendid butterflies have made me quite
envious, and at the same time have made me feel almost young again, so
vividly have they brought before my mind old days when I collected,
though I never made such captures as yours. Certainly collecting is the
best sport in the world. I shall be astonished if your book has not a
great success; and your splendid generalisations on geographical
distribution, with