Dear Sir

I am much obliged for your extremely courteous letter, together with your Essay & published papers.¹ Permit me to remark that you write excellent English—

It is well to try all sorts of hypotheses, but I do not feel inclined at present to place much trust in that suggested by you. Is not very long life rather rare with the Invertebrata? Considering that there would be no difference at first in structure, habits, or habitation between the first & last born offspring of any species, would they not be extremely liable to intercross,—for instance the children of the first born with the second born &c? According to your theory trees, some of which live for 1000–3000 years, would be particularly liable to have left first-born modified & later-born unmodified progeny; & is there any reason to believe that this has occurred?

In all cases it seems to me probable that the more highly modified & better adapted first-born progeny would displace & exterminate the less modified.

But as I have said it is well to consider all hypotheses, & with sincere good wishes for the success of your investigations, I remain | Dear Sir | Yours faithfully | Charles Darwin