I had better, perhaps, give Mr. Spencer’s own words as quoted by himself in his article in the _Nineteenth Century_ for April, 1886. He there wrote as follows, quoting from § 166 of his “Principles of Biology,” which appeared in 1864:— “Where the life is comparatively simple, or where surrounding circumstances render some one function supremely important, the survival of the fittest” (which means here the survival of the luckiest) “may readily bring about the appropriate structural change, without any aid from the transmission of functionally-acquired modifications” (into which effort and design have entered). “But in proportion as the life grows complex—in proportion as a healthy existence cannot be secured by a large endowment of some one power, but demands many powers; in the same proportion do there arise obstacles to the increase of any particular power, by ‘the preservation of favoured races in the struggle for life’” (that is to say, through mere survival of the luckiest). “As fast as the faculties are multiplied, so fast does it become possible for the several members of a species to have various kinds of superiority over one another. While one saves its life by higher speed, another does the like by clearer vision, another by keener scent, another by quicker hearing, another by greater strength, another by unusual power of enduring cold or hunger, another by special sagacity, another by special timidity, another by special courage; and others by other bodily and mental attributes. Now it is unquestionably true that, other things equal, each of these attributes, giving its possessor an equal extra chance of life, is likely to be transmitted to posterity. But there seems no reason to believe it will be increased in subsequent generations by natural selection. That it may be thus increased, the animals not possessing more than average endowments of it must be more frequently killed off than individuals highly endowed with it; and this can only happen when the attribute is one of greater importance, for the time being, than most of the other attributes. If those members of the species which have but ordinary shares of it, nevertheless survive by virtue of other superiorities which they severally possess, then it is not easy to see how this particular attribute can be developed by natural selection in subsequent generations.” (For if some other superiority is a greater source of luck, then natural selection, or survival of the luckiest, will ensure that this other superiority be preserved at the expense of the one acquired in the earlier generation.) “The probability seems rather to be, that by gamogenesis, this extra endowment will, on the average, be diminished in posterity—just serving in the long run to compensate the deficient endowments of other individuals, whose special powers lie in other directions; and so to keep up the normal structure of the species.