There are groups of species so closely allied together, that it needs the eye of a naturalist to distinguish them one from another.  If we disregard the small differences which separate these forms, and consider all the species of such groups as modifications of one type, we shall find that, even among the higher animals, some types have had a marvellous duration.  In the chalk, for example, there is found a fish belonging to the highest and the most differentiated group of osseous fishes, which goes by the name of Beryx.  The remains of that fish are among the most beautiful and well-preserved of the fossils found in our English chalk.  It can be studied anatomically, so far as the hard parts are concerned, almost as well as if it were a recent fish.  But the genus Beryx is represented, at the present day, by very closely allied species which are living in the Pacific and Atlantic Oceans.  We may go still farther back.  I have already referred to the fact, that the Carboniferous formations, in Europe and in America, contain the remains of scorpions in an admirable state of preservation and, that those scorpions are hardly distinguishable from such as now live.  I do not mean to say that they are not different, but close scrutiny is needed in order to distinguish them from modern scorpions.

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 as 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.