Now, it is self-evident that every one of these seven points is exactly what the theory of physiological selection requires, while there is not one of them which it does not require. For if the theory be sound, we should expect to find large numbers of species belonging to numerous and varied orders of plants presenting constant varieties on common areas; we should expect this to be a highly general, though not a universal, rule; and we should expect it to apply only to species which are indigenous. Moreover, we should expect these varieties, although but slightly differentiated morphologically, to present a great differentiation physiologically--and this in the special direction of selective fertility, combined, of course, with heredity. On the other hand, as I have said, this catalogue of evidences leaves nothing to be supplied. It gives us all the facts--and no more than all the facts--which my paper on _Physiological Selection_ anticipated as the eventual result of a prolonged experimental research. And if I have to regret my ignorance of these facts when that paper was published, at any rate it now furnishes the best proof that my anticipations were not guided by the results of a verification which had already been supplied. These anticipations were deduced exclusively from the theory itself, as representing what _ought_ to be the case if the theory were true; and, I must confess, if I had then been told that they had already been realized--that it had actually been found to be a general rule that endemic species present constant and hereditary varieties, intimately commingled on common areas, morphologically almost indistinguishable, but physiologically isolated by selective fertility--I should have felt that the theory had been verified in advance. For there are only two alternatives: either these things are due to physiological selection, or else they are due--as M. Jordan himself believes--to special creation. Which is equivalent to saying that, for evolutionists, the facts must be held to verify the former theory in as complete a manner as it is logically possible for the theory to be verified. _Evidence from Prepotency._ We have now to consider the bearing of what is called "prepotency" on the theory of physiological selection. Speaking of the vast number of species of Compositae, Darwin says:-- There can be no doubt that if the pollen of all these species could be simultaneously or successively placed on the stigma of any one species, this one would elect with unerring certainty its own pollen. This elective capacity is all the more wonderful, as it must have been acquired since the many species of this great group of plants branched off from a common progenitor.