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the chief reason why they express themselves in its favour with an enthusiasm, I might almost say with a fanaticism,” which would be incomprehensible in a purely scientific question. On the other hand, this is also the reason why scientific men and philosophers who do not share the materialistic views of Hæckel and Vogt, and theologians especially, attack Darwinism as a philosophical and theological heresy. For the present let us put aside the application of the Theory of Descent to men, and let us first of all examine the proofs of this theory as stated by Darwin.
theological objects. No doubt it is a mistake to do this, for the scientific inquirer should confine himself strictly to his object, which is to describe, calculate, and compare, and to discover laws. It is, the business of the theologian, not of the man of science, to harmonize these laws with the religious opinions of the present day. But Vogt is guilty of this very fault. He is almost more a theologian than a man of science, because he is always making incursions into theological regions, and trying to gain over converts to his own, that is, to atheistic opinions. For this reason, those who look in his works for information about Nature and her laws, and not for Vogt's own opinions, find that there is a purpose in them, and begin to suspect that in all scientific questions Vogt will take the side which is most decidedly antichristian and anti-biblical. Vogt formerly-although, considering his atheistic opinions, this has always surprised us-supported the theory of the immutability of species. Later on he eagerly embraced the Darwinian theory, and helped to extend it. Perhaps it may have attracted him, because, to use his own words, “we have now got rid of the Creator” (“es nun mit dem Schöpfer ganz vorbei sei”).
Hæckel puts Darwin next to Copernicus and Newton ; he calls his theory “the morning star of a new period in the history of human culture;” and says that the opposition to it is “a storm whose raging will for a long time divide the educated world.” Ueber die Entstehung, etc. p. 13. In the Gen. Morphologie, ii. p. 434, he says, “Many of the assertions made by the opponents of the Theory of Descent show such an astonishing want of natural, clear, and acute reasoning power that we should be warranted in placing those who make them lower than the more intelligent dogs, horses, and elephants. As these animals are mostly not hampered by the enormous mountains of dogmas and prejudices which pervert the thoughts of most men from their youth up, we often find that their judgment is more correct and natural than that of 'savants.'"
According to Darwin, all forms of plants and animals are descended from a few primæval forms, perhaps from one quite simple form. In order to establish this theory an unlimited mutability of organic forms must be supposed possible, in direct contradiction to the theory which obtained formerly, of the immutability of species in its essential qualities. Let us see, therefore, on what Darwin founds his theory.
It cannot be denied that the species of plants and animals are to a certain degree undefined and mutable. This is exemplified by cultivated plants and domestic animals, which separate into countless varieties and races. Take for instance the different races of dogs, cattle, horses, etc. ; the different sorts of fruit, grain, turnips, cabbage, and ornamental plants. These have originated by human selection ; the forms which were specially good were chosen out for reproduction, and these useful qualities were reproduced in the descendants and became hereditary. It was not in man's power to call forth these useful and pleasing qualities, but he had an opportunity of profiting by those which did exist, and of perpetuating them in the individuals which he bred."
A pigeon, for instance, has a few supernumerary tail feathers, which give it a peculiar appearance. The owner wishes to multiply this kind, he therefore allows the eggs of that pigeon to be hatched. He selects those among the young pigeons who display the same peculiarity; these he pairs, keeping the others away, and the peculiarity becomes a lasting one. He always selects those for breeding in whom the peculiarity is
* A. Müller, Veber die erste Entstehung organischer Wesen, und deren Spaltung in Arten, Berlin 1869, p. 18.
strongest, and thus the race of fantailed pigeons is produced. Or a gardener wishes to make a white flowering plant produce red blossoms. He chooses out from the different seedlings of the plant those which show any approach to red, and sows their seeds. Most of the plants thus produced show an inclination to red, a few will be redder than the first lot, and only the seed of these is sown. In the following generation the red will show itself still more strongly in some of the plants. If the selection is carried on through several generations, the gardener will at length obtain only red flowering plants. This mode of proceeding presupposes the following facts,-1. That individuals of the same kind are more or less different, and that these individual differences are universally connected with the conditions of the life, nourishment, surroundings, etc., of each individual. 2. That not only the common qualities of the kind, but also, at least in many cases, individual peculiarities, are inherited by the descendants.
We can see how far it is possible for a species to vary by taking the case of the pigeons, which Darwin has specially observed. Some races of pigeons are remarkable for a tuft of feathers on the back of the neck, forming a kind of hood; others have a strangely-shaped beak or feet; others are distinguished by peculiar, often very strange, ornaments; for instance some have a great development of skin about the head, or very large heads; others have peculiar habits, like the laugher pigeon, turtle dove, tumbler pigeon, etc. The differences extend to the internal structure, to the muscles and the skeleton. We find differences in the number of vertebræ and ribs, in the size and shape of bones, etc.
And yet Darwin thinks he has proved that all the races of pigeons are descended from a single wild stock, the blue rock (Columba Livia). The fact that certain peculiarities can be produced to order, shows how powerful artificial selection is, if it be properly carried out. An experienced English breeder offered to produce a certain feather in three years ; in order to produce a certain desired shape of the head or beak, he would, he said, require six years.
Taking these results of artificial breeding, Darwin says that something similar to this takes place among wild plants and animals in their natural state, and he gives to these processes the name of “natural breeding," or “natural selection.” Nature proceeds like man. It selects the individuals for breeding frome normous numbers. Each kind of plant and animal multiplies at such a rate that there is not room on the earth for all the individuals. According to Malthus' well-known statement, man increases in geometrical progression, while the quantity of food increases only in arithmetical progression. Hence man'sconstant struggle for the means of supporting existence,-means which are necessary, but not attainable by all. A similar struggle for existence takes place in the animal and vegetable world. Many, nay most individual plants and animals are destroyed before they come to their full development and are capable of reproduction. The earth has not room for all. From the beginning of its existence every organism struggles with a series of hostile influences; it struggles with animals who live on it, and whose natural food it is; it struggles with the temperature, weather, and similar influences ; above all, it struggles with other organisms like itself. Every
individual of the animal and vegetable world struggles for the necessary means of existence with other individuals of the same kind which live with it in the same place. For instance, in a thickly-sown wheat field only comparatively few of the numerous young plants which stand on a square foot can remain alive. They struggle with one another for the space which every plant requires in order to extend its roots; they struggle for sunlight and moisture; and in this struggle for life a few only win, the others perish,
But in this struggle for existence it is clear that the position of the separate individuals is quite unequal, the prospects of all are not equally favourable. This is caused, on the one hand, by the individual differences between individuals of the same kind, and, on the other, by many external conditions. Those individuals whose peculiarities harmonize best with the special external conditions, are most favourably placed ; and these favoured individuals will be successful in the struggle for existence, while the less favoured ones will be destroyed. For this reason Darwin employs the expression first originated by Herbert Spencer, the “Survival of the Fittest.” But those individuals who are favoured, or who are most suited to the conditions, do not only survive, but are able to reproduce themselves, while the less favoured ones die without leaving progeny. But if the individuals who reproduce themselves are those who are favoured in the struggle for existence, we learn from the experience of artificial selection that the peculiarities of those favoured individuals will not only be inherited, but will gradually increase, and be strengthened in the following generations, and that at