be that nearly two of them would survive, and have 200 children with an eighth superiority. Rather more than two of these would survive; but the superiority would again dwindle; until after a few generations it would no longer be observed, and would count for no more in the struggle for life than any of the hundred trifling advantages which occur in the ordinary organs. “‘An illustration will bring this conception home. Suppose a white man to have been wrecked on an island inhabited by negroes, and to have established himself in friendly relations with a powerful tribe, whose customs he has learnt. Suppose him to possess the physical strength, energy, and ability of a dominant white race, and let the food of the island suit his constitution; grant him every advantage which we can conceive a white to possess over the native; concede that in the struggle for existence, his chance of a long life will be much superior to that of the native chiefs; yet from all these admissions there does not follow the conclusion, that after a limited or unlimited number of generations, the inhabitants of the island will be white. Our shipwrecked hero would probably become king; he would kill a great many blacks in the struggle for existence; he would have a great many wives and children . . . In the first generation there will be some dozens of intelligent young mulattoes, much superior in average intelligence to the negroes. We might expect the throne for some generations to be occupied by a more or less yellow king; but can any one believe that the whole island will gradually acquire a white, or even a yellow population? . . . Darwin says, that in the struggle for life a grain may turn the balance in favour of a given structure, which will then be preserved. But one of the weights in the scale of nature is due to the number of a given tribe. Let there be 7000 A’s and 7000 B’s representing two varieties of a given animal, and let all the B’s, in virtue of a slight difference of structure, have the better chance by one-thousandth part. We must allow that there is a slight probability that the descendants of B will supplant the descendants of A; but let there be 7001 A’s against 7000 B’s at first, and the chances are once more equal, while if there be 7002 A’s to start, the odds would be laid on the A’s. Thus they stand a greater chance of being killed; but, then, they can better afford to be killed. The grain will only turn the scales when these are very nicely balanced, and an advantage in numbers counts for weight, even as an advantage in structure. As the numbers of the favoured variety diminish, so must its relative advantages increase, if the chance of its existence is to surpass the chance of its extinction, until hardly any conceivable advantage would enable the descendants of a single pair to exterminate the descendants of many thousands, if they and their descendants are supposed to breed freely with the inferior variety, and so gradually lose