More than this. At the very bottom of the Silurian series, in beds which are by some authorities referred to the Cambrian formation, where the signs of life begin to fail us--even there, among the few and scanty animal remains which are discoverable, we find species of molluscous animals which are so closely allied to existing forms that, at one time, they were grouped under the same generic name. I refer to the well-known _Lingula_ of the _Lingula_ flags, lately, in consequence of some slight differences, placed in the new genus _Lingulella._ Practically, it belongs to the same great generic group as the _Lingula,_ which is to be found at the present day upon your own shores and those of many other parts of the world. The same truth is exemplified if we turn to certain great periods of the earth's history--as, for example, the Mesozoic epoch. There are groups of reptiles, such as the _Ichthyosauria_ and the _Plesiosauria,_ which appear shortly after the commencement of this epoch, and they occur in vast numbers. They disappear with the chalk and, throughout the whole of the great series of Mesozoic rocks, they present no such modifications as can safely be considered evidence of progressive modification. Facts of this kind are undoubtedly fatal to any form of the doctrine of evolution which postulates the supposition that there is an intrinsic necessity, on the part of animal forms which have once come into existence, to undergo continual modification; and they are as distinctly opposed to any view which involves the belief, that such modification may occur, must take place, at the same rate, in all the different types of animal or vegetable life. The facts, as I have placed them before you, obviously directly contradict any form of the hypothesis of evolution which stands in need of these two postulates.