J.D.HOOKER TO CHARLES DARWIN.

November 9th, 1856.
I have finished the reading of your MS., and have been very much delighted and instructed.

Your case is a most strong one, and gives me a much higher idea of change than I had previously entertained; and though, as you know, never very stubborn about unalterability of specific type, I never felt so shaky about species before.
The first half you will be able to put more clearly when you polish up.
I have in several cases made pencil alterations in details as to words, etc., to enable myself to follow better,--some of it is rather stiff reading.

I have a page or two of notes for discussion, many of which were answered, as I got further on with the MS., more or less fully.
Your doctrine of the cooling of the Tropics is a startling one, when carried to the length of supporting plants of cold temperate regions; and I must confess that, much as I should like it, I can hardly stomach keeping the tropical genera alive in so very cool a greenhouse [pencil note by C.D., "Not so very cool, but northern ones could range further south if not opposed"].

Still I must confess that all your arguments pro may be much stronger put than you have.