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At a later period the human embryo is provided with a very conspicuous tail, which is considerably longer than the rudimentary legs occurring at that period of development, and which Professor Turner has found to be provided with muscles -the extensor, which is so largely developed in many animals, being especially well marked.

Again, as Mr. Darwin says, "In the embryos of all air-breathing vertebrates, certain glands, called the corpora Wolffiana, correspond with and act like the kidneys of mature fishes;" and during the sixth month the whole body is covered very thickly with wool-like hair-even the forehead and ears being closely coated; but it is, as Mr. Darwin observes, "a significant fact that the palms of the hands and the soles of the feet are quite naked, like the inferior surfaces of all four extremities in most of the lower animals," including monkeys.

Lastly, Professor Wyman has found that in a

human embryo about an inch in length, "the great toe was shorter than the others; and, instead of being parallel to them, projected at an angle from the side of the foot, thus corresponding with the permanent condition of this part in the quadrumana.” 1

Therefore, on the whole, we may conclude these brief remarks on embryology with the words of Professor Huxley :-"Without question, the mode of origin, and the early stages of the development of man, are identical with those of the animals immediately below him in the scale; without a doubt, in these respects he is far nearer to apes than the apes are to the dog." 2

1 Proc. Amer. Acad. Scs., vol. iv., 1860, p. 17. It should be added, however, that although the direction taken by the great toe of man at this early age is doubtless, as Prof. Wyman states, more like that which obtains in the quadrumana, there is a slight anatomical difference in the mode of its articulation with the foot, which seems to assist in securing the forward direction taken by it in later life.

2 Man's Place in Nature, p. 65.

VI.

ARGUMENTS DRAWN FROM CERTAIN GENERAL

CONSIDERATIONS.

THERE are two or three arguments of a somewhat weighty character, which do not fall under any of the previous headings, but which we must not on this account neglect.

1. It is justly deemed a substantiation of a scientific theory if it is found to furnish an explanation of other classes of phenomena than those for the explanation of which it was first devised. And this is the case with the theory of natural selection in the region of psychology. The theory was first devised to explain the

facts of biology, and proving so successful in that region, Mr. Darwin proceeded to test it in the region of psychology. The result has been to show that large classes of phenomena in this region which were previously unaccountable become fully intelligible. This is especially the case with the phenomena of instinct, and in a lesser degree with those of reason and conscience. For the theory shows that if structures admit of being moulded to their special uses by natural selection, the same must be true of instincts; and it is found an easy matter to understand how, by seizing upon and fixing, through hereditary beneficial variations of habit (whether instinctive or intelligent), natural selection is as competent to fashion the mental structure of an animal as it is to shape its bodily structure into agreement with the external conditions of life. Thus the whole philosophy of animal intelligence is greatly elucidated,

and this fact may justly be regarded as lending much additional credence to the theory.

Again, by observing that sympathy and the social instincts generally are developed to a large extent in many of the lower animals, and particularly so in the quadrumana, the theory of natural selection is provided with a reasonable basis for furnishing a scientific explanation of the moral sense in man; and by observing that many of the lower animals are capable of drawing simple inferences, the theory is likewise able to explain the development of reason. So that in the province of human psychology no less than in that of animal, the theory of natural selection, in showing itself competent to explain much which is otherwise inexplicable, is seen to derive a large additional measure of argumentative support.

2. Although the majority of structures and instincts met with in the animal kingdom are

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