To John Lubbock 14 [July 1857]1
My dear Lubbock
You have done me the greatest possible service in helping me to clarify my Brains. If I am as muzzy on all subjects as I am on proportions & chance,—what a Book I shall produce!—
I have divided N. Zealand Flora as you suggested. There are 339 species in genera of 4 & upwards & 323 in genera of 3 & less. The 339 species have 51 species presenting one or more varieties—2 The 323 species have only 37: proportionally (as 339:323 \:\: 51.:48.5) they ought to have had 48 species presenting vars.— So that the case goes as I want it, but not strong enough, without it be general, for me to have much confidence in.
I am quite convinced yours is the right way; I had thought of it, but shd never have done it, had it not been for my most fortunate conversation with you.
I am quite shocked to find how easily I am muddled, for I had before thought over the subject much, & concluded my way was fair. It is dreadfully erroneous. What a disgraceful blunder you have saved me from. I heartily thank you—3
Ever yours | C. Darwin
It is enough to make me tear up all my M.S. & give up in despair.—
It will take me several weeks to go over all my materials. But oh if you knew how thankful I am to you.—
Thanks JL for saving him from "a disgraceful blunder". Following their conversation he has divided the New Zealand flora as JL suggested and finds genera with four or more species are more variable than those with three or less. It will take several weeks to go back over all his material.