I am very glad to hear that you mean to attack this subject some day.

I wonder whether we shall ever be public combatants; anyhow, I congratulate myself in a most unfair advantage of you, viz., in having extracted more facts and views from you than from any one other person.

I daresay your explanation of polymorphism on volcanic islands may be the right one; the reason I am curious about it is, the fact of the birds on the Galapagos being in several instances very fine-run species--that is, in comparing them, not so much one with another, as with their analogues from the continent.

I have somehow felt, like you, that an alpine form of a plant is not a true variety; and yet I cannot admit that the simple fact of the cause being assignable ought to prevent its being called a variety; every variation must have some cause, so that the difference would rest on our knowledge in being able or not to assign the cause.

Do you consider that a true variety should be produced by causes acting through the parent?
But even taking this definition, are you sure that alpine forms are not inherited from one, two, or three generations?
Now, would not this be a curious and valuable experiment (16/1.