"Entstehung und Begriff der Naturhistorischen Art," an Address given before the Royal Academy of Sciences at Munich, March 28th, 1865.

See "Life and Letters," III., page 50, for Mr.Darwin's letter to the late Prof.Nageli.) I find on consideration it would be too long; for so good a pamphlet ought to be discussed at full length or not at all.

He makes a mistake in supposing that I say that useful characters are always constant.

His view about distinct species converging and acquiring the same identical structure is by implication answered in the discussion which I have given on the endless diversity of means for gaining the same end.
The most important point, as it seems to me, in the pamphlet is that on the morphological characters of plants, and I find I could not answer this without going into much detail.
The answer would be, as it seems to me, that important morphological characters, such as the position of the ovules and the relative position of the stamens to the ovarium (hypogynous, perigynous, etc.) are sometimes variable in the same species, as I incidentally mention when treating of the ray-florets in the Compositae and Umbelliferae; and I do not see how Nageli could maintain that differences in such characters prove an inherent tendency towards perfection.

I see that I have forgotten to say that you have my fullest consent to append any discussion which you may think fit to the new edition.