Natural Selection.

As Natural Selection which works so slowly is a main element in Mr. Darwin's theory, it is necessary to understand distinctly what he means by it. On this point he leaves us no room for doubt. On p. 92, he says: "This preservation of favorable variations, and the destruction of injurious variations, I call Natural Selection, or, the Survival of the Fittest." "Owing to the struggle (for life) variations, however slight and from whatever cause proceeding, if they be in any degree profitable to the individuals of a species, in their infinitely complex relations to other organic beings and to their physical conditions of life, will tend to the preservation of such individuals, and will generally be inherited by their offspring. The offspring also will thus have a better chance of surviving, for, of the many individuals of any species which are periodically born, but a small number can survive. I have called this principle, by which each slight variation, if useful, is preserved, by the term Natural Selection, in order to mark its relation to man's power of selection. But the expression often used by Mr. Herbert Spencer of the Survival of the Fit

test, is more accurate, and sometimes is equal-
ly convenient." (p. 72). "Slow though the
progress of selection may be, if feeble man can
do so much by artificial selection, I can see no
limit to the amount of change, to the beauty
and infinite complexity of the co-adaptations
between all organic beings, one with another,
and with their physical conditions of life, which
may be effected in the long course of time by
nature's power of selection, or the survival of
the fittest." (p. 125). "It may be objected that
if organic beings thus tend to rise in the scale,
how is it that throughout the world a multi-
tude of the lowest forms still exist; and how
is it that in each great class some forms are
far more highly developed than others?
On our theory the continuous existence of
lowly forms offers no difficulty; for natural
selection, or the survival of the fittest, does not
necessarily include progressive development,
it only takes advantage of such variations as
arise and are beneficial to each creature under
its complex relations of life. . . . . Geology
tells us that some of the lowest forms, the in-
fusoria and rhizopods, have remained for an
enormous period in nearly their present state."
(p. 145). "The fact of little or no modifica-

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tion having been effected since the glacial period would be of some avail against those who believe in an innate and necessary law of development, but is powerless against the doctrine of natural selection, or the survival of the fittest, which implies only that variations or individual differences of a favorable nature occasionally arise in a few species and are then preserved." (p. 149)

This process of improvement under the law of natural selection includes not only changes in the organic structure of animals, but also in their instincts and intelligence. On entering on this part of his subject, Mr. Darwin says, "I would premise that I have nothing to do with the origin of the primary mental powers, any more than I have with that of life itself. We are concerned only with the diversities of instinct and of other mental qualities within the same class.” (p. 255) ▼ He shows that even in a state of nature the instincts of animals of the same species do in some degree vary, and that they are transmitted by inheritance. A mastiff has imparted courage to a greyhound, and a greyhound has transmitted to a shepherd-dog a disposition to hunt hares. Among sporting dogs, the young of the pointer or retriever

have been known to point or to retrieve without instruction. "If," he says, "it can be shown that instincts do vary ever so little, then I can see no difficulty in natural selection preserving and continually accumulating variations of instinct to any extent that was profitable. It is thus, as I believe, that all the most complex and wonderful instincts have arisen.' (p. 257) He was rather unguarded in saying that he saw no difficulty in accounting for the most wonderful instincts of animals. He admits that he has found very great difficulty. He selects three cases which he found it specially hard to deal with that of the cuckoo, that of the cell-building bee, and of the slavemaking ant. He devotes much space and labor in endeavoring to show how the instinct of the bee, for example, in the construction of its cell, might have been gradually acquired. It is clear, however, that he was not able fully to satisfy even his own mind; for he admits that "it will be thought that I have an overweening confidence in the principle of natural selection, when I do not admit that such wonderful and well established facts do not annihilate the theory." (p. 290) This remark was made with special reference to the instincts

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of the ant, which he finds very hard to account for. He adds, "No doubt many instincts of very difficult explanation could be opposed to the theory of natural selection: cases in which we cannot see how an instinct could possibly have originated; cases in which no intermediate gradations are known to exist; cases of instinct of such trifling importance that they could hardly have been acted upon by natural selection; cases of instincts almost identically the same in animals so remote in the scale of nature, that we cannot account for their similarity by inheritance from a common progenitor, and consequently cannot believe that they were independently acquired through natural selection. I will not here enter on those cases, but will confine myself to one special difficulty which at first appeared to me insuperable, and actually fatal to the whole theory. I allude to neuters, or sterile females in insect communities; for these neuters often differ widely in instinct and structure from both the males and the fertile females, and yet, from being sterile, they cannot propagate their kind." (p. 289) He is candid enough to say, in conclusion, "I do not pretend that the facts given in this chapter (on instinct) strengthen