by surrounding conditions, improves or decays, without mixing with neighbouring groups.

Summing up these preliminary observations on the theory that missing links " are by no means so necessary on a fair showing of Nature's ways and polity as might be supposed, we may submit, firstly, that the favourable variation of a species is a slow process, depending not merely on changes in the constitution of the included animals or plants, but on many other external causes, such as changes of climate, and the like. Secondly, in connection with this first discouragement to the mixing of specific characters, we must remember that detachment of land-surfaces will account for the absence of intermediate forms, and in cases where such forms have existed, they would be developed, as we have seen, in fewer numbers than the species they would tend to connect; lesser numbers implying few chances of either actual or geological preservation.

But we may not forget that up to the present stage we have been merely contending for the relevancy of the indictment. Supposing our objections to the invariable necessity for "missing links" have been maintained, there yet remain very many instances wherein, as the evolutionist would freely admit, such connections require to be supplied, theoretically or actually, for the support of his case. The connected chain of life which the evolutionist postulates, implies the presence of numerous links; the chief question relating to the exact stages or points at which these links are demanded—and this question again depending on another, What is or was the exact sequence and order of development? Suppose Mr. Browning to be as correct in his poetic rendering of the "Descent of Man" as he is-judged by ordinary theories of evolution-absolutely incorrect, when he says in "Prince Hohenstiel Schwangau

That mass man sprang from was a jelly lump
Once on a time; he kept an after course
Through fish and insect, reptile, bird, and beast,
Till he attained to be an ape at last

Or last but one,

then, according to the poet's rendering of man's evolution, his descent would imply connecting links between the amoeboid or protoplasm stage of his existence and the "after course," and also between the successive stages of which that "after course" is alleged to consist. Fortunately for scientific criticism, poetry possesses an invaluable commodity known as "licence;" and it may suffice in the present instance to remark that the sequence and succession of life indicated by the most psychological of modern poets, are VOL, CCXLV, NO. 1785.

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certainly not those held by Mr. Darwin, or by any other competent biologist. Man's descent from the gorilla-the chief element in the evolutionist's creed as propounded by popular notions and by a dogmatic but unlearned theology-is, after all, but "the baseless fabric" of a vision, from which a better acquaintance with the facts of nature and with theories explanatory of these facts, will most effectually awaken the unconvinced. The knowledge of what evolution really teaches and reasonably demands constitutes, therefore, the first condition for ascertaining what "missing links" are required. To bridge over the gulf between the gorilla or any other anthropoid ape and the human type, may be the mental bane and lifelong worry of unscientific minds contorting the demands of evolution-such a task is certainly no business or labour of Mr. Darwin and his followers, or of any other school of evolution. And Mr. Darwin, writing in his "Descent of Man," and after a review of man's theoretical origin, is careful to add, "but we must not fall into the error of supposing that the early progenitor of the whole Simian (or ape-like) stock, including man, was identical with, or even closely resembled, any existing ape or monkey." We must, in truth, look backwards along the "files of time" to the point whence, from a common origin, the human and ape branches diverged each towards its own peculiar line of growth and development on the great tree of life.

Thus much by way of caution in alleging how or what "missing links" are to be supplied. The contention that, even on the showing of the evolutionist, the connecting links between distinct groups of living beings are not supplied even to the extent he himself requires, is answered in the expression of Mr. Darwin already quoted, namely, "the imperfection of the geological record." No fact of geology is more patent than that, to use Sir Charles Lyell's words, "it is not part of the plan of Nature to write everywhere, and at all times, her autobiographical memoirs. On the contrary," continues this late distinguished scientist, "her annals are local and exceptional from the first, and portions of them are afterwards ground into mud, sand, and pebbles, to furnish materials for new strata." The very process of rock-formation consists in the re-arrangement of the particles of previously formed materials, and the manufacture of new strata implies the destruction of the old with the included "fossils" of the latter. The geological series is thus certainly a detached and discontinuous collection of formations, interrupted by gaps of considerable and often undeterminable extent. Of the contemporaneous life-history of the globe, during the periods of time represented by such gaps, we have no record whatever. But even when the materials for form

ing a detailed history of any past period of our globe are found in tolerable plenty, the record is never complete. "We can never hope," says Lyell in a most emphatic passage on breaks in the sequence of rock-formations, "to compile a consecutive history by gathering together monuments which were originally detached and scattered over the globe. For, as the species of organic beings contemporaneously inhabiting remote regions are distinct, the fossils of the first of several periods which may be preserved in any one country, as in America, for example, will have no connection with those of a second period found in India, and will, therefore, no more enable us to trace the signs of a gradual change in the living creation, than a fragment of Chinese history will fill up a blank in the political annals of Europe." Add to these considerations the brief chronicle of a long and important chapter of geological history, namely, that soft-bodied animals and plants are rarely preserved as fossils; that land-animals are but sparsely represented in any formations as compared with marine forms; and that even "Metamorphism," or the alteration of rocks subsequent to their formation, is known to alter and obliterate their fossil-contents, and we find reasons of the most stable and satisfactory kind for the imperfect nature of even the fullest records of rocks and of their fossils that man has been able to obtain.

But in what direction does the positive evidence we have been able to obtain lead? Clearly to the side of evolution, and towards the supply of "missing links" in a fashion which even the most sanguine expectations of scientific ardour could scarcely have hoped to see realised. Bearing in mind that vast tracts of rock-formations are as yet absolutely unexplored, the present subject is seen to be one to which each year brings its quota of new and strange revelations. And at the most, any one record of what has been done towards supplying "missing links," must be held to be merely provisional and to serve but as a prelude to the discoveries of a succeeding period. Especially within the last few years, however, has the evidence of the existence of animals which may fairly be deemed "missing links" accumulated in a very marked degree, and in some cases in a very astonishing fashion. The reader has but to become informed of recent discoveries amidst the Tertiary rocks of North America, to learn the surprising revelations concerning intermediate forms between existing groups of mammals or quadrupeds, which, chiefly through the researches of Professor Marsh, have been added to the conquests of science. What, for example, is to be said of the zoological position of the huge Dinoceras (Fig. 1) and its allies, creatures as large as existing elephants, and which, from the examination of their skeletal

remains, can at the best be regarded as intermediate betwixt the elephants themselves, and the odd-toed Ungulates (or hoofed

"missing links," can be assigned to the extinct quadrupeds, included by Marsh under the collective name Tillodontia, the remains of which occur in the Eocene Tertiaries of the United States? For, how else should we classify animals with great front teeth like the Rodents or "gnawers," grinders like the Ungulates or hoofed quadrupeds, and a skull and skeleton generally like that of the Carnivorous Bears? Or, once more, what can be said of the affinities or relationship of the extinct Toxodonts, also from American deposits, in which the characters of rodents are united to those of Ungulates and Edentates-the latter being a group of animals represented by the existing sloths, armadillos, and anteaters? Nor is the list of extinct quadrupeds which fall into no existing group, but present a union of the characters of several distinct divisions, exhausted with the foregoing brief chronicle. Again drawing upon the well-nigh inexhaustible treasure-house of geological specimens in the recent deposits of the New World, we find

FIG. 2.

the extinct Marauchenia connecting the odd-toed hoofed mammals with the even-toed division. Passing to the whales and their kin, we find the extinct Zeuglodon with its well-developed teeth-a fea

ture unusual in living whales-appearing to connect the whale-tribe with the seals and their allies. Similarly, the curious Anoplotherium

(Fig. 3) of the Eocene Tertiary deposits appears to connect the swinerace with the true cud-chewers or Ruminants, just as the Palæotherium (Fig. 2) itself-one of the first animals whose remains were disinterred from Montmartre— connects the pigs and tapirs with the apparently far-removed rhinoceros. The case for the existence of "missing links," wherewith the at present distinct orders and sub-orders of quadrupeds may be connected, would

FIG. 3.

seem to be very strong. There would appear to be more than sufficient cause to account for the hopeful spirit of the evolutionist, whose scientific prophecy, that philosophic research into the nature of fossil organisms-begun by Cuvier, in the now classical quarries of Montmartre is destined to powerfully aid his cause, seems likely to be realised. When it lies in the power of the naturalist to point, as well he may, with pride, to the perfect series of forms and missing links which connect the one-toed horse of to-day with the curious three, four, and five-toed steeds of the past,' one may overlook the jubilant tone of the evolutionist in the more silent and deeper satisfaction with which mankind at large is given to welcome the demonstration of a great truth. It is of such a demonstration that Huxley writes: "On the evidence of paleontology, the evolution of many existing forms of animal life from their predecessors is no longer an hypothesis, but an historical fact; it is only," he adds, "the nature of the physiological factors to which that evolution is due which is still open to discussion."

But not merely in the highest class of the animal world have "intermediate forms" been discovered. The case for evolution grows in interest when we learn that in lower ranks of Vertebrate life, groups of animals, separated apparently by the widest of intervals, are now being linked together by the discovery of intermediate fossil forms. The best-known example of the latter facts is found in the relationship which may be now regarded as being clearly proved to exist between reptiles and birds. Were we to search the whole animal kingdom through for examples of creatures of thoroughly different appearance, habits, and general conformation, no two groups would fall more familiarly to hand than birds and reptiles. There would, indeed, appear to be no similarity or likeness between 'See Gentleman's Magazine for March 1879, article on "Clues and Traces in Natural History."