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Show 48 THE PAST CONDITION layers of stone in the earth's crust are, defective as they necessarily are as a record, the account of. cont emporaneous vital phenomena presented by the:U 1s, by the necessity of the case, infinitely more defective and fragmentary. It was necessary that I should put all this very ·strongly before you, because, otherwise, you might l! ave been led to think differently of the completeness of our knowledge by the next facts I shall state to you. The researches of the last three-quarters of a century have, in truth, revealed a wonderful richness of organic life in those rocks. Certainly not fewer than t hirty or forty thousand different species of fossils have been discovered. You have no more ground for doubting that these creatures really lived and died at or near the places in which we find them than you have for like scepticism about a shell on the sea-shore. 'The evidence is as good in the one case as in the ·other. Our next business is to look at the general character of these fossil remains, and it is a subject which will be requisite to consider carefully; and the first point for us is to examine how n1uch the extinct Flora and Fauna as a whole-disregarding altogether the succession of t heir constituents, of which I shall speak afterwardsdiffer from the Flora and Fauna of the present day;how far they differ in what we do know about them, leaving altogether out of consideration speculations based on what-we do not know. I strongly imagine that if it were not for the pe. culiar appearance that fossilized animals have, that ·any of you might readily walk through a museum OF ORGANIC NA1'URE. which contains fossil remains mixed up with those of the present forms of life, and I doubt very much whether your uninstructed eyes would lead you to see any vast or wonderful difference between the two. If you looked closely, you would notice, in the first place, a great many things very like animals 'Yith which you are acquainted now : you would see differences of shape and proportion,. but on the whole a close similarity. I explained what I meant by ORDERS the other day, when I described the animal kingdom as being divided in sub-kingdoms, classes, and orders. If you divide the animal kingdom into orders, you. will find that there are above one hundred and twenty. The number may vary on one side or the other, but this is a fair estimate. That is the sun1 total of the orders of all the animals which we know now, and which have been known in past times, and left remains behind. Now, how many of those are absolutely extinct ?' That is to say, how many of these orders of animals have lived at a former period of the world's history, but have at present no representatives ?' That is the sense in which I meant to use the word "extinct." I mean that those animals did live on this earth at one time, but have left no one of their kind with us at the present moment. So that estimating the number of extinct animals is a sort of way of comparing the past creation as a whole with the present as a whole. To make that clear, I have written in red ink on these diagrams the names of all those extinct orders, and in black ink the names of |