of toleration; for in the latter case the individuals of one generation would as effectually poison themselves with larger doses, as did the individuals of preceding generations with smaller doses.
In fact, evolution against alcohol and opium tends to place the race in the same position as regards them as it already holds in relation to nicotine; that is, it tends to bring about such a diminution of the depth of the intoxication desired that the individual is no longer placed at a disadvantage in the struggle for existence by reason of his craving; but in the case of opium, the narcotic in relation to which the individual is himself able to undergo a great protective reaction, this evolution appears much easier of achievement than in the case of alcohol, the narcotic against which the individual is able to undergo comparatively little protective reaction; for while the evolution against alcohol, as we have seen, is only perfected after the lapse of many centuries of stringent Alcoholic Selection, the evolution against opium appears to be perfected, as we shall, see, in a much shorter space of time—in quite a few centuries. It appears, therefore, that in the case of opium, the narcotic which resembles nicotine, in that it is a toxin, and in that the individual reaction to it is great, the race with comparative ease achieves a position in relation to it similar to that which it holds in relation to nicotine; but in the case of alcohol, the narcotic which is dissimilar from nicotine in that it is a waste product, and in that the individual reaction to it is comparatively little, the race achieves a like position in relation to it only with great difficulty and after many centuries of selection. In fact, efficient protective evolution against opium appears to result from a much smaller divergence from the susceptible ancestral type than does efficient protective evolution against alcohol.
It has already been remarked that, after having con-
