12th October, 1965.
Dear Jacques,
Be reasonable.  Of course you meant to compare the properties of a tetramer and a monomer assuming the same for both.  You not only intended to do it, but you did it.  Nevertheless it was unfair.  Unfair to whom?  Unfair to the monomer, of course.  After all, why keep L the same for the monomer?  It turns out that it is not unreasonable to keep alpha and c the same - let us assume this anyway, for the sake of argument.  Then why not let "Mother Nature" choose L to have the best value, whatever one may mean by that, to give the monomer a fair chance.  Who are you to say that the poor monomer has to have L = 1000 rather than the obviously superior value of 4 square root 1000, which I assume?  The main point of my model is to show that such a monomer is not unreasonable.  As I stated, it is inferior to the tetramer but not by as much as you made out.
I am at the moment engaged in a further paper (The Price of Allostery).  I suggest that I hold my footnote till you come to London in December, and we can have a full discussion then.  Do you think you and Jeffries could come to Cambridge for a couple of days?  It would also give us the chance to discuss next summer with Odile.  And I think we should talk about the Salk.
F. H. C. Crick