Every such speculation must be rejected, because it is self-contradictory. It professes to develop a Theory of Creation, -- to explain the beginning of things; and in order to do so, it is obliged to assume that the present or ordinary succession of phenomena, the common sequence of causes and effects which we every day witness, has continued from eternity; -- that is, that there never was any Creation, and that the universe never began to be. It professes to untie the knot, and ends by denying that there is any knot to untie. Mr. Darwin is too imaginative a thinker to be a safe guide in natural science; he has unconsciously left the proper ground of physics and inductive science, and busied himself with questions of cosmogony and metaphysics.

Numerous Species of the same genus now coexist, often within the bounds of a not very extended territory, without any one of them showing any tendency to supplant or exterminate another. Thus, South Africa is the country par excellence of the antelope; about fifty species of this animal have been found there, many of them very abundant, notwithstanding the numerous Carnivora that prey upon them, and yet none of them showing any tendency to die out before civilized man came thither and brought gunpowder along with him.

If the indications from analogy, on which the whole speculation is based, are so faint that the work cannot have been completed except in an infinite lapse of years, these indications practically amount to nothing.  The evidence which needs to be multiplied by infinity before it will produce conviction, is no evidence at all.

And though only one out of a hundred of these Individual Variations is transmitted by inheritance, yet, after collecting as many instances of such transmission as they can find, they affirm that a Variation tends to become hereditable. But it is not so. Tendency is rightly inferred only from the majority of cases; a small minority of favorable instances merely shows the tendency to be the other way. Thus, the cars do not tend to run off the track, although one train out of a thousand may be unlucky enough to do so; but the general law is, that they remain on the track.

the direct evidence fails altogether, and we are left exclusively to the guidance of conjecture and analogy and estimates of what is possible for all that we know to the contrary.

And generally, putting aside the question whether the offspring of certain races when crossed are entirely sterile or only partially so, there is no doubt that animals or plants belong to distinct Species when they cannot be crossed or made to interbreed at all. It is enough to say, then, that only Cumulative Variation -- and that of a vast number of successive steps -- will account for the common origin of animals which will not copulate with each other, or of plants which cannot be crossed.  

But with whatever success the doctrine of Inherited Variation may be applied to explain the existence of Varieties, it is certain that the origin of Species can be accounted for on the Development Theory, if at all, only by Cumulative Variation, -- that is, only by supposing a vast number of Inherited Variations to be successively superinduced one upon another. Doubts have been raised upon this point only on account of ambiguity in the meaning of words, or from want of agreement as to the principles of classification. Many races, both of animals and vegetables, appear to be so nearly allied to each other, that certain naturalists consider them as mere Varieties; others persist in considering them as so many distinct Species.