e. Unless these breed together, a most improbable event, their
progeny would again approach the average individual; there would be 150 of
them, and their superiority would be, say in the ratio of one and a quarter
to one; the probability would now 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 and climate 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 {59}
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 of life by 1/7000 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 only 7001 A's agai