“Nothing can be more hopeless than to attempt to explain this similarity of pattern in members of the same class by utility or the doctrine of final causes . . . _On the ordinary view of the independent creation of each being_, we can only say that so it is . . . _The explanation is manifest on the theory of the natural selection of successive slight_ modifications,” &c. (p. 435).
This now stands—“The explanation is to a large extent simple, on the theory of the selection of successive, slight modifications.” I do not like “a large extent” of simplicity; but, waiving this, the point at issue is not whether the ordinary course of things ensures a quasi-selection of the types that are best adapted to their surroundings, with accumulation of modification in various directions, and hence wide eventual difference between species descended from common progenitors—no evolutionist since 1750 has doubted this—but whether a general principle underlies the modifications from among which the quasi-selection is made, or whether they are destitute of such principle and referable, as far as we are concerned, to chance only. Waiving this again, we note that the theories of independent creation and of natural selection are contrasted, as though they were the only two alternatives; knowing the two alternatives to be independent creation and descent with modification, we naturally took natural selection to mean descent with modification.
“_On the theory of natural selection_ we can satisfactorily answer these questions” (p. 437).
“Satisfactorily” now stands “to a certain extent.”
“_On my view_ these terms may be used literally” (pp. 438, 439).
“On my view” became “according to the views here maintained such language may be,” &c., in 1869.
“I believe all these facts can be explained as follows, _on the view of descent with modification_” (p. 443).
“Let us take a genus of birds, _descended_, _on my theory_, _from some one parent species_, and of which the several new species _have become modified through natural selection_ in accordance with their divers habits” (p. 446).
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.”