all be anxious to see how Pangenesis is
received.--Believe me yours very faithfully,

ALFRED R. WALLACE.

* * * * *

_Down, Bromley, Kent, S.E. February 27, 1868._

My dear Wallace,--You cannot well imagine how much I have been pleased
by what you say about Pangenesis. None of my friends will speak out,
except, to a certain extent, Sir H. Holland,[67] who found it very tough
reading, but admits that some view "closely akin to it" will have to be
admitted. Hooker, as far as I understand him, which I hardly do at
present, seems to think that the hypothesis is little more than saying
that organisms have such and such potentialities. What you say exactly
and fully expresses my feeling, viz. that it is a relief to have some
feasible explanation of the various facts, which can be given up as soon
as any better hypothesis is found. It has certainly been an immense
relief to my mind; for I have been stumbling over the subject for years,
dimly seeing that some relation existed between the various classes of
facts. I now hear from H. Spencer that his views quoted in my footnote
refer to something quite distinct, as you seem to have perceived.

I shall be very glad to hear, at some future day, your criticisms on the
causes of variability.

Indeed, I feel sure that I am right about sterility and Natural
Selection. Two of my grown-up children who are acute reasoners have two
or three times at intervals tried to prove me wrong, and when your
letter came they had another try, but ended by coming back to my side. I
do not quite understand your case, and we think that a word or two is
misplaced. I wish some time you would consider the case under the
following point of view. If sterility is caused or accumulated through
Natural Selection, then, as every degree exists up to absolute
barrenness, Natural Selection must have the power of increasing it. Now
take two species, A and B, and assume that they are (by any means)
half-sterile, i.e. produce half the full number of offspring. Now try
and make (by Natural Selection) A and B absolutely sterile when crossed,
and you will find how difficult it is. I grant, indeed it is certain,
that the degree of sterility of the individuals of A and B will vary,
but any such extra-sterile individuals of, we will say, A, if they
should hereafter breed with other individuals of A, will bequeath no
advantage to their progeny, by which these families will tend to
increas