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every event in nature must have a certain cause, and must, if it occurs, occur according to fixed and definite laws. But still we may talk of chance if by it we mean events whose occurrence the known course of the laws of nature does not lead us to expect; whose reason and whose law is hidden from us, and which on this account we do not recognise as belonging to any plan, and cannot foresee and calculate, and ascribe to a certain cause. The origin of some small useful or harmful change in an organism, even when it is produced by some cause or other, is a chance in this sense,”—for the change need not occur, and does not occur in many cases. “Natural selection only begins to work when this chance variation has taken place," and here again it is affected by the occurrence of circumstances which need not occur, and in fact do not always occur; and whose actual occurrence in any given case is therefore also a matter of

chance. “So that at last the Darwinian theory gives . us a principle whose reason, law, and necessity, that is, whose true essence is unknown to us, and which we therefore cannot well consider as a certain principle of knowledge or of interpretation.”

This objection no doubt would vanish if we were to suppose that the Creator, who, to use Darwin's expression, breathed life with its several powers into one form from which the endless forms of the organic world have been evolved, that the Creator gave to this original form the power and tendency to develop, and that according to design He brought about the conditions favourable to this development. But Darwin cannot assume this, and still less can his followers, for then

" Das Christenthum, p. 495.

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the Creator, Preserver, and Guider of the world, whom, to use Vogt's expression, they have turned out at one door, would come in again by another, and in a grander form than before ; for the power and wisdom of God would be shown much more overwhelmingly if He had caused the whole organic world to be evolved, as the Darwinian theory describes it, from one primordial form than if He had created it at once. But if the designed and provident action of a higher Power be denied, and consistent Darwinians must deny it, nothing is left but chance.

And again, on the one hand Darwin is obliged to assume that changes in organic beings occur easily and often, on the other hand that the changes which have occurred are often and easily perpetuated and become hereditary. But these two principles of mutability and of inheritance and perpetuation do not as a matter of fact usually co-operate, but, on the contrary, are often antagonistic. In proportion to the facility with which changes occur is it difficult for the changed organisms to become distinct species, and while, on the one hand, by assuming that the existing species can be modified we produce a likelihood of change, on the other hand it is difficult to stop these changes, because it is only in rare cases that the outward conditions of nature are so fixed and unchangeable as not at once to give occasion for fresh changes.

Darwin no doubt relies on the enormously long period, on the millions of years which must have elapsed before these accumulated small changes can have produced differences of species which are clearly distinguishable before the differences in species become as fixed and lasting as we see them now ;—so lasting that at the present time artificially produced varieties easily sink back into the regular species if they are no longer looked after. But, as Frohschammer rightly observes,' “ these millions of years at most explain the accumulation of changes, the growth of differences in species, and their confirmation. They do not explain how it came about that first the gradual slow change went on for an immeasurably long period, then ceased, and in another immeasurably long period became established, and then how, lastly, fresh slight changes and gradual transformations took place after so long a period of rest for no apparent reason. These enormously long periods, with which Darwin is so lavish, only make the process possible in time, but they do not explain why it took place; nor do they give the reason for the alternation in the process which accordingly appears to be casual, without principle or law. However immeasurably long we may suppose this period to be, its length alone cannot have caused a series of evolutions to take place, then to pause, and then to begin again. If two lines are really exactly parallel, they will not approach each other by a hair's breadth, even if they are prolonged to all eternity. And so also immeasurable periods cannot produce what time, whether short or long, cannot cause. Be it long or short, we want another cause to explain the beginning and continuation of a process of evolution. And further, it is uncertain whether we are justified in assuming that these long periods of time have passed during the development of the organic world; and for

1 Frohschammer, Op. cit. p. 496.

1 Frohschammer, Op. cit. p. 497.

this reason they are not sufficient to explain the phenomena.” We are moving in a circle, we assume immeasurable periods of time, because we think by this means to explain the origin of the multiplicity of organic beings, and we then support the assumption by saying that without it we cannot account for the origin of this very multiplicity.

It is also rather hazardous to assume that small imperceptible changes have originated in organisms, and that these changes can only become really noticeable differences of species by accumulation in an immeasurably long period of time. “If these changes were so small as to be imperceptible, natural selection could not well make use of them in order to preserve and further to develop those organic forms to which they were peculiar, and therefore no sufficient foundation exists for natural selection. But if we were to suppose that these changes were great enough directly to afford a real advantage in the struggle for existence, their origin becomes more difficult to understand, and according to the Darwinian theory it is totally inexplicable.” 1

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· Frohschammer, Op. cit. p. 499.

XXVII.

THE THEORY OF DESCENT—Conclusion.

It is of course impossible to give in a few lectures an exhaustive account and criticism of the theory of descent, and of the explanation of it given by Darwin and his followers. I have been obliged to confine myself to its main outlines, and to a few details chosen as examples. You will find in the works which I have so often quoted of Frohschammer, Huber, J. B. Meyer, A. Wigand, and Pfaff, more detailed discussions in a form which can be understood by every educated man.

To-day I wish shortly to discuss two general considerations, much relied on by Hæckel, who, as you know, likes general, or, as he calls them, philosophical arguments. The first consideration is connected with the so-called natural system of the animal and vegetable world. Animals—of whom alone we will speak

-were divided by Cuvier into four great divisions (branches), the vertebrata, articulata, mollusca, and radiata. Later zoologists have substituted for the radiata the two groups of the echinoderma and the coelenterata or zoophytes; and for the articulata the two groups of the arthropoda and the vermes; and have formed another group, the protozoa, out of the infusoria and the spongiadæ, so that in all there are

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