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anticipate the results of these indispensable observations, and to say that because it is possible that they may lead to a conclusion favourable to the theory of descent, therefore this theory may be considered as correct, although the results of inquiry have been hitherto unfavourable to it. The least we may expect is that the supporters of the theory should admit that it is not yet proved; that, on the contrary, there are still weighty objections to it; and we can only wait to see whether the progress of research will remove these objections, and give us better reasons for believing in the theory than we have at present.
Huxley, who is one of the most learned and acute supporters of the theory of descent, openly acknowledges the difficulty which lies in the fact of the fertility of races, but the sterility of species, that have intercrossed. He says, “ There is, in fact, one set of these peculiarities which the theory of selective modification, as it stands at present; is not wholly competent to explain, and that is the group of phenomena which I mentioned to you under the name of Hybridism, and which I explained to consist in the sterility of the offspring of certain species when crossed one with another. It matters not one whit whether this sterility is universal, or whether it exists only in a single case Every hypothesis is bound to explain, or at any rate not be inconsistent with 'the whole of the facts which it professes to account for; and if there is a single one of these facts which can be shown to be inconsistent with (I do not merely mean inexplicable by, but contrary to) the hypothesis, the hypothesis falls to the
1 J. B. Meyer, Philos. Zeit fragen, p. 73.
ground,—it is worth nothing. One fact with which it is positively inconsistent is worth as much, and is as powerful in negativing the hypothesis, as five hundred. If I am right in thus defining the obligations of an hypothesis, Mr. Darwin, in order to place his views beyond the reach of all possible assault, ought to be able to demonstrate the possibility of developing from a particular stock by selective breeding, two forms, which should either be unable to cross one with another, or whose cross bred offspring should be infertile one with another.” For in this case only would it be proved that new species could be formed whose intercrossing is not lastingly fertile, whereas so long as the intercrossing remained lastingly fertile, there would be nothing but new races. Huxley continues, "Now it is admitted on all hands that, at present, so far as experiments have gone, it has not been found possible to produce this complete physiological divergence by selective breeding. . . . So far as we have gone yet with our breeding, we have not produced from a common stock two breeds which are not more or less fertile with one another.” Huxley then observes that he does not know of any fact which could justify the assertion that such sterility cannot be produced by proper experimentation, and that he himself sees every reason for believing that it may and will be so produced. And he ends with these words : “ So that though Mr. Darwin's hypothesis does not completely extricate us from this difficulty at present, we have not the least right to say that it will not do
i On our Knowledge, etc. Lect. vii. p. 149 seq.
Qui vivra, verra. At any rate Darwinians have no right to assert that their leader's hypothesis is proved. On the contrary, the way in which we are continually put off with possibilities when we compare the theory with actual facts, raises well founded doubts as to the theory itself. Even with reference only to what I have spoken of—and the principal point is still to come,—I think we may say with J. B. Meyer,' that “ Darwinism is not condemned because it sets up hypotheses, but because these hypotheses are bad. No science can exist without hypotheses, and good hypotheses may be of great service to a science. But we can only admit them in order to explain existing facts ; and we cannot admit those hypotheses which require for their support not only other hypotheses, but also facts which are entirely unproved. Now the Darwinian theory requires many such hypotheses, and therefore it is scientifically wrong and inadmissible.”?.
The explanation of undoubted facts is here rightly said to be the object of scientific hypotheses. The more completely and simply a hypothesis explains the facts in question, the more plausible it is. I have shown by several examples that the Darwinian theory does not explain many important facts, or at least cannot explain them without having recourse to further hypotheses. There are no doubt certain groups of facts in the face of which the Darwinian theory appears to a superficial observer an attractive, and according to its supporters the only satisfactory hypothesis. The
1 Philos. Zeitfragen, p. 103. 2 Cf. Hæckel, Nat. Schöpfungsgeschichte, p. 126. Anthropogenie, pp. 86, 692. existence of the so-called rudimentary organs belongs to these. By the rudimentary organs are meant those parts of the body which are intended for a special purpose, and yet have no functions. In some animals which live in caves or under the earth, and which therefore can never use their eyes, we find hidden under the skin real eyes, or something resembling real eyes, but these eyes cannot perform their functions because they are covered with an opaque membrane, and therefore cannot be reached by the light. It is supposed that in the ancestors of these animals, which lived in the daylight, the eyes were well developed, were covered by a horny transparent capsule, and actually served the purpose of seeing. As the animals accustomed themselves by degrees to an underground mode of life, and withdrew from the light of day, they no longer used their eyes, the latter then deteriorated more and more from generation to generation, so that at last only the rudiments of eyes remained. Darwin explains that the wings of those birds and insects which live in islands, and therefore need not fly much or far, grow stunted in this way. He goes farther, and assumes that those kinds of birds which are called running birds, whose legs, like those of the ostrich and cassowary are strongly developed, and whose wings are very slightly developed, are descended from birds which had stronger wings, that they had got out of the habit of flying, had thus lost the use of their wings, and had therefore preserved only rudimentary wings.
The stunting of the wings among birds and insects
which lived on islands is explained in this manner; those that flew well and much were while flying blown by the wind into the sea; those that flew ill therefore had in this case an advantage in the struggle for existence, they were not so easily blown into the sea, and remained alive longer than individuals of the same kind that flew well. And therefore, in the course of of several generations, the wings became gradually stunted by the process of natural selection. For instance, in the island of Madeira, out of five hundred and fifty kinds of beetles, two hundred had no wings, or wings so imperfect as to make flying impossible. No doubt it is not unlikely that a gradual stunting actually took place among many species of birds, but it is rather hazardous to generalize from this, and to explain all the so-called rudimentary organs in this way. It is possible that among many species the rudimentary form of the organ is the original one, and that it stands in its proper relation to the whole organization. If organs which are not used not only gradually grow stunted but at last disappear, we cannot understand why several of the so-called rudimentary organs, if they are really useless to the animal, have not disappeared altogether; as, for instance, the nipples in male mammals, and the rudimentary toes at the side of a horse's foot. It does not follow that because the ostrich has wings like all other birds, therefore it ought to have equally useful wings, and that its ancestors must have had wings as useful as those of the eagle. If we assume this, we are suppos
1 Hæckel, Nat. Schöpfungsgeschichte, p. 223. 2 Huber, Zur Kritik, p. 14. Michelis, Hæckelogonie, p. 80.