This passage was altered in 1869 to “The bond is simply inheritance.” The paragraph concludes, “_On this principle of inheritance with modification_, we can understand how it is that sections of genera . . . are confined to the same areas,” &c. Again:— “He who rejects it rejects the _vera causa of ordinary_ generation,” &c. (p. 352). We naturally ask, Why call natural selection the “main means of modification,” if “ordinary generation” is a _vera causa_? Again:— “In discussing this subject, we shall be enabled at the same time to consider a point equally important for us, namely, whether the several distinct species of a genus, _which on my theory have all descended from a common ancestor_, can have migrated (undergoing modification during some part of their migration) from the area inhabited by their progenitor” (p. 354). The words “on my theory” became “on our theory” in 1869. Again:— “With those organic beings which never intercross (if such exist) _the species_, _on my theory_, _must have descended from a succession of improved varieties_,” &c. (p. 355). The words “on my theory” were cut out in 1869. Again:— “A slow southern migration of a marine fauna will account, _on the theory of modification_, for many closely allied forms,” &c. (p. 372). Again:— “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. Again:— “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). “My theory” became “our theory” in 1869. Again:— “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? Again:— “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).