If the earliest organism could have only varied favourably in one direction, the one possible favourable accidental variation would have accumulated so long as the organism continued to exist at all, inasmuch as this would be preserved whenever it happened to occur, while every other would be lost in the struggle of competitive forms; but even in the lowest forms of life there is more than one condition in respect of which the organism must be supposed sensitive, and there are as many directions in which variations may be favourable as there are conditions of the environment that affect the organism.  We cannot conceive of a living form as having a power of adaptation limited to one direction only; the elasticity which admits of a not being “extreme to mark that which is done amiss” in one direction will commonly admit of it in as many directions as there are possible favourable modes of variation; the number of these, as has been just said, depends upon the number of the conditions of the environment that affect the organism, and these last, though in the long run and over considerable intervals of time tolerably constant, are over shorter intervals liable to frequent and great changes; so that there is nothing in Mr. Charles Darwin’s system of modification through the natural survival of the lucky, to prevent gain in one direction one year from being lost irretrievably in the next, through the greater success of some in no way correlated variation, the fortunate possessors of which alone survive.  This, in its turn, is as likely as not to disappear shortly through the arising of some difficulty in some entirely new direction, and so on; nor, if function be regarded as of small effect in determining organism, is there anything to ensure either that, even if ground be lost for a season or two in any one direction, it shall be recovered presently on resumption by the organism of the habits that called it into existence, or that it shall appear synchronously in a sufficient number of individuals to ensure its not being soon lost through gamogenesis.

How is progress ever to be made if races keep reversing, Penelope-like, in one generation all that they have been achieving in the preceding?  And how, on Mr. Darwin’s system, of which the accumulation of strokes of luck is the greatly preponderating feature, is a hoard ever to be got together and conserved, no matter how often luck may have thrown good things in an organism’s way?  Luck, or absence of design, may be sometimes almost said to throw good things in our way, or at any rate we may occasionally get more through having made no design than any design we should have been likely to have formed would have given us; but luck does not hoard these good things for our use and make our wills for us, nor does it keep providing us with the same good gifts again and again, and no matter how often we reject them.

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 section 166 of his “Principles of Biology,” which appeared in 1864:-