“In the first place, it should always be borne in mind what sort of intermediate forms must, on my theory, formerly have existed” (p. 280).
“My theory” became “the theory” in 1869. No reader who read in good faith could doubt that the theory of descent with modification was being here intended.
“It is just possible by my theory, that one of two living forms might have descended from the other; for instance, a horse from a tapir; but in this case direct intermediate links will have existed between them” (p. 281).
“My theory” became “the theory” in 1869.
Again:—
“By the theory of natural selection all living species have been connected with the parent species of each genus,” &c. We took this to mean, “By the theory of descent with modification all living species,” &c. (p. 281).
Again:—
“Some experienced conchologists are now sinking many of the very fine species of D’Orbigny and others into the rank of varieties; and on this view we do find the kind of evidence of change which on my theory we ought to find” (p. 297).
“My theory” became “the theory” in 1869.
In the fourth edition (1866), in a passage which is not in either of the two first editions, we read (p. 359), “So that here again we have undoubted evidence of change in the direction required by my theory.” “My theory” became “the theory” in 1869; the theory of descent with modification is unquestionably intended.