The Pamphlet Collection of Sir Robert Stout: Volume 29
Ladies and Gentlemen—In my last lecture I had occasion to place before you evidence derived from fossil remains, which, as I stated, was perfectly consistent with the doctrine of Evolution, was favourable to it, but could not be regarded as the highest kind of evidence before that sort of evidence that we call demonstrative.
I pointed out, in fact, that as we go back in time, the great intervals which at present separate the larger divisions of animals become more or less completely obliterated by the appearance of intermediate forms, so that, if we take the particular case of reptiles and birds, upon which I dwelt at length, we find in the mesozoic rocks animals which, if ranged in scries, would so completely bridge over the interval between the reptile and the bird that it would be very hard to say where the reptile ends and where the bird begins. Evidence so distinctly favourable as this of Evolution, is far weightier than that upon which men undertake to say that they believe many important propositions; but it is not the highest kind of evidence attained, for this reason, that, as it happens the intermediate forms to which I have referred do not occur in the exact order in which they ought to occur, if they really had formed steps in the progression from the reptile to the bird: that is to say, we find these forms in contemporaneous deposits, whereas, the requirements of the demonstrative evidence of Evolution demand, that we should find the series of gradations between one group of animals and another in such order as they must have followed if they had constituted a succession of stages in time, of the development of the form at which they ultimately arrive. That is to say, the complete evidence of the page 29 evolution of the bird from the reptile—what I call the demonstrative evidence, because it is the highest form of this class of evidence—that evidence should be of this character, that in some ancient formation reptiles alone should be found; in some later formations birds should first be met with, and in the intermediate forms we should discover in regular succession forms which I have pointed out to you which are intermediate between the reptile and the birds.