LETTER 333. 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. I am more reconciled to iceberg transport than I was, the more especially as I will give you any length of time to keep vitality in ice, and more than that, will let you transport roots that way also.

(333/1. The above letter was pinned to the following note by Mr. Darwin.)

In answer to this show from similarity of American, and European and Alpine-Arctic plants, that they have travelled enormously without any change.

As sub-arctic, temperate and tropical are all slowly marching toward the equator, the tropical will be first checked and distressed, similarly (333/2. Almost illegible.) the temperate will invade...; after the temperate can [not] advance or do not wish to advance further the arctics will be checked and will invade. The temperates will have been far longer in Tropics than sub-arctics. The sub-arctics will first have to cross temperate [zone] and then Tropics. They would penetrate among strangers, just like the many naturalised plants brought by man, from some unknown advantage. But more, for nearly all have chance of doing so.

(333/3. The point of view is more clearly given in the following letters.)