My second son, the mathematician, thinks that you have omitted one almost inevitable deduction which apparently would modify the result.

He has written out what he thinks, but I have not tried fully to understand him.

I suppose that you do not care enough about the subject to like to see what he has written.
LETTER 212A.

A.R.WALLACE TO CHARLES DARWIN.

Hurstpierpoint, March, 24th [1868].
I return your son's notes with my notes on them.