I do not think that this is strictly true, for I occasionally sounded
not a few naturalists, and never happened to come across a single one
who seemed to doubt about the permanence of species. Even Lyell and
Hooker, though they would listen with interest to me, never seemed to
agree. I tried once or twice to explain to able men what I meant by
Natural Selection, but signally failed. What I believe was strictly
true is that innumerable well-observed facts were stored in the minds
of naturalists ready to take their proper places as soon as any theory
which would receive them was sufficiently explained. Another element
in the success of the book was its moderate size; and this I owe to the
appearance of Mr. Wallace's essay; had I published on the scale in which
I began to write in 1856, the book would have been four or five times as
large as the 'Origin,' and very few would have had the patience to read
it.

I gained much by my delay in publishing from about 1839, when the theory
was clearly conceived, to 1859; and I lost nothing by it, for I cared
very little whether men attributed most originality to me or Wallace;
and his essay no doubt aided in the reception of the theory. I was
forestalled in only one important point, which my vanity has always made
me regret, namely, the explanation by means of the Glacial period of
the presence of the same species of plants and of some few animals on
distant mountain summits and in the arctic regions. This view pleased me
so much that I wrote it out in extenso, and I believe that it was read
by Hooker some years before E. Forbes published his celebrated memoir
('Geolog. Survey Mem.,' 1846.) on the subject. In the very few points in
which we differed, I still think that I was in the right. I have never,
of course, alluded in print to my having independently worked out this
view.

Hardly any point gave me so much satisfaction when I was at work on
the 'Origin,' as the explanation of the wide difference in many classes
between the embryo and the adult animal, and of the close resemblance of
the embryos within the same class. No notice of this point was taken, as
far as I remember, in the early reviews of the 'Origin,' and I recollect
expressing my surprise on this head in a letter to Asa Gray. Within late
years several reviewers have given the whole credit to Fritz Muller and
Hackel, who undoubtedly have worked it out much more fully, and in some
respects more correctly than I did.