So that just as an undefined amount of use and disuse was introduced on the earlier page to supplement the effects of natural selection in respect of the wings of beetles on small and exposed islands, we have here an undefined amount of natural selection introduced to supplement the effects of use and disuse in respect of the identical phenomena. In the one passage we find that natural selection has been the main agent in reducing the wings, though use and disuse have had an appreciable share in the result; in the other, it is use and disuse that have been the main agents, though an appreciable share in the result must be ascribed to natural selection. Besides, who has seen the uncles and aunts going away with the uniformity that is necessary for Mr. Darwin's contention? We know that birds and insects do often get blown out to sea and perish, but in order to establish Mr. Darwin's position we want the evidence of those who watched the reduction of the wings during the many generations in the course of which it was being effected, and who can testify that all, or the overwhelming majority, of the beetles born with fairly well-developed wings got blown out to sea, while those alone survived whose wings were congenitally degenerate. Who saw them go, or can point to analogous cases so conclusive as to compel assent from any equitable thinker? Darwinians of the stamp of Mr. Thiselton Dyer, Professor Ray Lankester, or Mr. Romanes, insist on their pound of flesh in the matter of irrefragable demonstration. They complain of us for not bringing forward some one who has been able to detect the movement of the hour-hand of a watch during a second of time, and when we fail to do so, declare triumphantly that we have no evidence that there is any connection between the beating of a second and the movement of the hour-hand. When we say that rain comes from the condensation of moisture in the atmosphere, they demand of us a rain-drop from moisture not yet condensed. If they stickle for proof and cavil on the ninth part of a hair, as they do when we bring forward what we deem excellent instances of the transmission of an acquired characteristic, why may not we, too, demand at any rate some evidence that the unmodified beetles actually did always, or nearly always, get blown out to sea, during the reduction above referred to, and that it is to this fact, and not to the masterly inactivity of their fathers and mothers, that the Madeira beetles owe their winglessness? If we began stickling for proof in this way, our opponents would not be long in letting us know that absolute proof is unattainable on any subject, that reasonable presumption is our highest certainty, and that crying out for too much evidence is as bad as accepting too little. Truth is like a photographic sensitised plate, which is equally ruined by over and by under exposure, and the just exposure for which can never be absolutely determined.