cal or mechanical, and have reference only to future conditions of life after the foetus has passed into what may be truly called a new living world. In like manner, while in the foetal state, neither man nor any mammal has need of a double heart. The foetus is resting in a dark chamber surrounded by a watery fluid; and a simple heart we believe (on the analogy shewn to us by the hearts of fishes) would best suit its state of being. A simple heart is given to it, not however the heart either of a fish or a reptile; but a heart with a structure of its own, and with appendages

a true and inseparable portion of itself-whereby a new double heart is gradually laid down and perfected. When this complicated apparatus has reached perfection, and the fœtus becomes capable of supporting an independent life, then it passes into the air, and the double heart begins from that moment its predestined organic movements. I have only stated facts which have been stated a thousand times before. I have stated them as plainly as I can; and I have given them their true physiological and moral meaning. Thine eyes did see my substance yet being imperfect, and in thy book all my members were written, which in continuance were fashioned, when as yet there was none of them. This is the voice of inspiration, and reaches the profoundest depths of true philosophy. The knowledge of man can neither add to its meaning nor diminish its strength. teaches not that the moral parts of our nature are sunk under the material; neither does it tell us that the material are beneath the contemplation of the moral;

It

but it unites together the moral and material in bonds which the power of man will never tear asunder.

All living Nature then, so far as I can understand her language, or can read the interpretations of it by other men, contradicts the theory of spontaneous generation and progressive development. Spontaneous generation (in our Author's sense) has not one good unambiguous fact to rest upon. The theory of development has no firmer support in nature: and the only pretended fact which has any clear and unequivocal bearing on the question, and is put forth by the Author of The Vestiges, with the view of destroying the separation between vegetable species, turns out to be nothing better than a misconception and a blunder*.

It has been said, however, that animals undergo a progressive development while they pass through their successive foetal conditions in the womb. True! and many of them, while in the larva state, leave the ovum, and are enabled for a time to support an independent life. But larvae, when they leave the ovum, have no sexual development; and can never without a miracle (for what is a miracle but a violation of an ascertained law of nature?) have the power of generating any new continued forms of animal being. And were it true, by a miracle in nature, that any one of them were suddenly endowed with this power, the development would then be on a descending, and not on an ascending scale. Again, we have been told that animals may, under favourable conditions, Supplement to the Appendix No. IV.

and by a longer period of gestation, produce some being of a higher order than themselves: that a beast (for example) may in this way be hatched from a bird's egg; and that woman may hereafter make perfect the organic scale, by producing some being of higher attributes than man! What beings may be produced out of the abortive imaginations of the human brain, is not a question worth one moment's pause. So far as nature is concerned, philosophy has nothing to do with what may be, but with what is.

§ 4. Organic Phenomena of Geology, and general remarks on their bearing on the Theory of Development.

Leaving the consideration of living nature, another question may be started: Are there, among the old deposits of the Earth, any traces of an organic progression among the successive forms of life? I think there are such traces; and to explain my meaning, I will quote an extract from an Anniversary Address read by myself before the Geological Society of London, in 1831. "I think that in the repeated and almost entire changes of organic types in the successive strata of the earth in the absence of mammalia in the older, and their very rare appearance (and then in forms entirely unknown. to us) in the newer secondary groups—in the diffusion of warm-blooded quadrupeds (frequently of unknown genera) in the older tertiary system; and in their great abundance (and frequently of known genera) in the upper portions of the same series-and lastly, in the

recent appearance of man on the surface of the Earth (now universally admitted);-in one word, from all these facts combined, we have a series of proofs the most emphatic and convincing,—that the existing order of nature is not the last of an uninterrupted succession of mere physical events derived from laws now in daily operation: but on the contrary, that the approach to the present system of things has been gradual, and that there has been a progressive development of organic structures subservient to the purposes of life.

"Considered as a mere question of physics (and keeping all moral considerations entirely out of sight), the appearance of man is a geological phenomenon of vast importance-indirectly modifying the whole surface of the earth-breaking in upon any supposition of zoological continuity-and utterly unaccounted for by what we have any right to call the Laws of Nature. If by the laws of nature we mean only such manifestations of power as seem good to the Supreme Intelligence, then there can be no matter for dispute. But in physical questions such terms as 'the laws of nature,' have a proper reference only to second causes; and I may ask, by what operation of second causes can we account for the recent appearance of man*?"

I wish to make no change in the previous extract. Its language might be improved, and brought into more exact accordance with the advance of knowledge during the last twenty years: but it expresses, with sufficient clearness, what may be called a great historical truth;

Proceedings of the Geological Society. London, Vol. 1. p. 305.

and the words " progressive development" have (in the sentences just quoted) no reference to any theory either true or false. At the time it was written I neither believed in the spontaneous generation, nor in the specific transmutations of any portion of the animal kingdom. Let no one, therefore, quote this passage without allowing its author to define the meaning of his own words*.

Three great divisions of the fossiliferous strata. Considered under the most general and simple point of view, the fossil-bearing strata of the earth admit of an arrangement into three great divisions; the Primary, or Paleozoic; the Secondary; and the Tertiary.-In the lowest groups of the Primary division neither landplants nor air-breathing marine animals have yet been found; but other marine animals are found in abundance, and some of them are of the very highest organic type. In the upper groups of the same division we have a noble terrestrial flora; and coeval with that flora were Insects and Reptiles. In the very highest group (the Permian) bones of Reptiles had long been discovered but remains of the reptile Class have lately been found also in the Carboniferous strata.

Among the Secondary rocks-including under that name all the formations, from the new red sandstone

* A historical development is, or ought to be, a record of successive facts in the past phenomena of the organic world. A theory of development may be true or false; but must not be confounded with a mere statement of the successive facts on which it is supposed to rest. In the remaining portions of this Preface the word development may sometimes be used historically; but the words theory of development are always used with an expressed or implied reference to the hypothesis of a progressive natural development by specific transmutations.