With respect to trees on islands, I collected some cases, but took the main facts from Alph. De Candolle, and thought they might be trusted. My explanation may be grossly wrong; but I am not convinced it is so, and I do not see the full force of your argument of certain herbaceous orders having been developed into trees in certain rare cases on continents. The case seems to me to turn altogether on the question whether generally herbaceous orders more frequently afford trees and bushes on islands than on continents, relatively to their areas. (110/5. In the "Origin," Edition I., page 392, the author points out that in the presence of competing trees an herbaceous plant would have little chance of becoming arborescent; but on an island, with only other herbaceous plants as competitors, it might gain an advantage by overtopping its fellows, and become tree-like. Harvey writes: "What you say (page 392) of insular trees belonging to orders which elsewhere include only herbaceous species seems to me to be unsupported by sufficient evidence. You cite no particular trees, and I may therefore be wrong in guessing that the orders you allude to are Scrophularineae and Compositae; and the insular trees the Antarctic Veronicas and the arborescent Compositae of St. Helena, Tasmania, etc. But in South Africa Halleria (Scrophularineae) is often as large and woody as an apple tree; and there are several South African arborescent Compositae (Senecio and Oldenburgia). Besides, in Tasmania at least, the arborescent Composites are not found competing with herbaceous plants alone, and growing taller and taller by overtopping them...; for the most arborescent of them all (Eurybia argophylla, the Musk tree) grows...in Eucalyptus forests. And so of the South African Halleria, which is a tree among trees. What the conditions of the arborescent Gerania of the Sandwich Islands may be I am unable to say...I cannot remember any other instances, nor can I accept your explanation in any other of the cases I have cited.")
In page 4 of your letter you say you give up many book-species as separate creations: I give up all, and you infer that our difference is only in degree and not in kind. I dissent from this; for I give a distinct reason how far I go in giving up species. I look at all forms, which resemble each other homologically or embryologically, as certainly descended from the same species.
You hit me hard and fairly (110/6. Harvey writes: "You ask--were all the infinitely numerous kinds of animals and plants created as eggs or seed, or as full grown? To this it is sufficient to reply, was your primordial organism, or were your four or five progenitors created as egg, seed, or full grown? Neither theory attempts to solve this riddle, nor yet the riddle of the Omphalos." The latter point, which Mr. Darwin refuses to give up, is at page 483 of the "Origin," "and, in the case of mammals, were they created bearing the false marks of nourishment from the mother's womb?" In the third edition of the "Origin," 1861, page 517, the author adds, after the last-cited passage: "Undoubtedly these same questions cannot be answered by those who, under the present state of science, believe in the creation of a few aboriginal forms, or of some one form of life. In the sixth edition, probably with a view to the umbilicus, he writes (page 423): "Undoubtedly some of these same questions," etc., etc. From notes in Mr. Darwin's copy of the second edition it is clear that the change in the third edition was chiefly due to Harvey's letter. See Letter 115.) about my question (page 483, "Origin") about creation of eggs or young, etc., (but not about mammals with the mark of the umbilical cord), yet I still have an illogical sort of feeling that there is less difficulty in imagining the creation of an asexual cell, increasing by simple division.
Page 5 of your letter: I agree to every word about the antiquity of the world, and never saw the case put by any one more strongly or more ably. It makes, however, no more impression on me as an objection than does the astronomer when he puts on a few hundred million miles to the distance of the fixed stars.