I am not at all surprised that Hallett has found some varieties of wheat could not be improved in certain desirable qualities as quickly as at first.

All experience shows this with animals; but it would, I think, be rash to assume, judging from actual experience, that a little more improvement could not be got in the course of a century, and theoretically very improbable that after a few thousands [of years] rest there would not be a start in the same line of variation.

What astonishes me as against experience, and what I cannot believe, is that varieties already improved or modified do not vary in other respects.
I think he must have generalised from two or three spontaneously fixed varieties.

Even in seedlings from the same capsule some vary much more than others; so it is with sub-varieties and varieties.

(230/1.