ght have presented another
occasion for ventilating them.--Yours sincerely,

W.T. THISELTON-DYER.

* * * * *

SIR W.T. THISELTON-DYER TO A.R. WALLACE

_The Ferns, Witcombe, Gloucester. July 11, 1909._

Dear Mr. Wallace,-- ... I have just got F. Darwin's "Foundations." He
tries to make out that his father could have dispensed with Malthus. But
the selection death-rate in a slightly varying large population is _the_
pith of the whole business. The Darwin-Wallace theory is, as you say,
"the continuous adjustment of the organic to the inorganic world." It is
what mathematicians call "a moving equilibrium." In fact, I have always
maintained that it is a mathematical conception.

It seemed to me there was a touch of insincerity about the whole
celebration,[37] as the younger Cambridge School as a whole do not even
begin to understand the theory.... I take it that the reason is, as you
pointed out, that none of them are naturalists.--Yours sincerely,

W.T. THISELTON-DYER.

* * * * *

TO DR. ARCHDALL REID

_Old Orchard, Broadstone, Dorset. December 28, 1909._

Dear Dr. Archdall Reid,--Many thanks for your very interesting and
complimentary letter. I am very glad to hear of your new book, which I
doubt not will be very interesting and instructive. The subjects you
treat are, however, so very complex, and require so much accurate
knowledge of the facts, and so much sound reasoning upon them, that I
cannot possibly undertake the labour and thought required before I
should feel justified in expressing an opinion upon your treatment of
them....

I rejoice to hear that you have exposed the fallacy of the claims of the
Mendelians. I have also tried to do so, but I find it quite impossible
for me to follow their detailed studies and arguments. It wants a
mathematical mind, which I have not.

But on the general relation of Mendelism to Evolution I have come to a
very definite conclusion. This is, that it has no relation whatever to
the evolution of species or higher groups, but is really antagonistic to
such evolution! The essential basis of evolution, involving as it does
the most minute and all-pervading adaptation to the whole environment,
is extreme and ever-present plasticity, as a condition of survival and
adaptation. But the essence of Mendelian characters is their rigidity.
They are transmitted without variation, and therefore, except by the
rare