The words “on my theory” were cut out in 1869, and the passage now stands, “Let us take a group of birds, descended from some ancient form and modified through natural selection for different habits.” Again:— “_On my view of descent with modification_, the origin of rudimentary organs is simple” (p. 454). “On my view” became “_on the view_” in 1869. Again:— “_On the view of descent with modification_,” &c. (p. 455). Again:— “_On this same view of descent with modification_ all the great facts of morphology become intelligible” (p. 456). Again:— “That many and grave objections may be advanced against _the theory of descent with modification through natural selection_, I do not deny” (p. 459). This now stands, “That many and serious objections may be advanced against _the theory of descent with modification through variation and natural selection_, I do not deny.” Again:— “There are, it must be admitted, cases of special difficulty _on the theory of natural selection_” (p. 460). “On” has become “opposed to;” it is not easy to see why this alteration was made, unless because “opposed to” is longer. Again:— “Turning to geographical distribution, the difficulties encountered _on the theory of descent with modification_ are grave enough.” “Grave” has become “serious,” but there is no other change (p. 461). Again:— “As _on the theory of natural selection_ an interminable number of intermediate forms must have existed,” &c. “On” has become “according to”—which is certainly longer, but does not appear to possess any other advantage over “on.” It is not easy to understand why Mr. Darwin should have strained at such a gnat as “on,” though feeling no discomfort in such an expression as “an interminable number.” Again:— “This is the most forcible of the many objections which may be urged _against my theory_ . . . For certainly, _on my theory_,” &c. (p. 463). The “my” in each case became “the” in 1869. Again:— “Such is the sum of the several chief objections and difficulties which may be justly urged _against my theory_” (p. 465). “My” became “the” in 1869. Again:— “Grave as these several difficulties are, _in my judgment_ they do not overthrow _the theory of descent with modifications_” (p. 466). This now stands, “Serious as these several objections are, in my judgment they are by no means sufficient to overthrow _the theory of descent with subsequent modification_;” which, again, is longer, and shows at what little, little gnats Mr. Darwin could strain, but is no material amendment on the original passage. Again:— “_The theory of natural selection_, even if we looked no further than this, _seems to me to be in itself probable_” (p. 469).