The words “on my theory” were cut out in 1869.
“A slow southern migration of a marine fauna will account, _on the theory of modification_, for many closely allied forms,” &c. (p. 372).
“But the existence of several quite distinct species, belonging to genera exclusively confined to the southern hemisphere, is, _on my theory of descent with modification_, a far more remarkable case of difficulty” (p. 381).
“My” became “the” in 1866 with the fourth edition. This was the most categorical claim to the theory of descent with modification in the “Origin of Species.” The “my” here is the only one that was taken out before 1869. I suppose Mr. Darwin thought that with the removal of this “my” he had ceased to claim the theory of descent with modification. Nothing, however, could be gained by calling the reader’s attention to what had been done, so nothing was said about it.
“Some species of fresh-water shells have a very wide range, _and allied species_, _which_, _on my theory_, _are descended from a single source_, prevail throughout the world” (p. 385).
“In the following remarks I shall not confine myself to the mere question of dispersal, but shall consider some other facts which bear upon the truth of _the two theories of independent creation and of descent with modification_” (p. 389). What can be plainer than that the theory which Mr. Darwin espouses, and has so frequently called “my,” is descent with modification?
“But as these animals and their spawn are known to be immediately killed by sea-water, _on my view_, we can see that there would be great difficulty in their transportal across the sea, and therefore why they do not exist on any oceanic island. But why, _on the theory of creation_, they should not have been created there, it would be very difficult to explain” (p. 393).
On the following page we read—“On my view this question can easily be answered.” “On my view” is retained in the latest edition.
“Yet there must be, _on my view_, some unknown but highly efficient means for their transportation” (p. 397).
“On my view” became “according to our view” in 1869.
“I believe this grand fact can receive no sort of explanation _on the ordinary view of independent creation_; whereas, _on the view here maintained_, it is obvious that the Galapagos Islands would be likely to receive colonists . . . from America, and the Cape de Verde Islands from Africa; and that such colonists would be liable to modification; the principle of inheritance still betraying their original birth-place” (p. 399).