In the year 1866 appeared A. Murray's work on the "Geographical Distribution of Mammals", a book which has perhaps received less recognition than it deserves. His treatment of the general introductory questions marks a considerable advance of our problem, although, and partly because, he did not entirely agree with Darwin's views as laid down in the first edition of "The Origin of Species", which after all was the great impulse given to Murray's work. Like Forbes he did not shrink from assuming enormous changes in the configuration of the continents and oceans because the theory of descent, with its necessary postulate of great migrations, required them. He stated, for instance, "that a Miocene Atlantis sufficiently explains the common distribution of animals and plants in Europe and America up to the glacial epoch." And next he considers how, and by what changes, the rehabilitation and distribution of these lands themselves were effected subsequent to that period. Further, he deserves credit for having cleared up a misunderstanding of the idea of specific centres of creation. Whilst for instance Schmarda assumed without hesitation that the same species, if occurring at places separated by great distances, or apparently insurmountable barriers, had been there created independently (multiple centres), Lyell and Darwin held that each species had only one single centre, and with this view most of us agree, but their starting point was to them represented by one individual, or rather one single pair. According to Murray, on the other hand, this centre of a species is formed by all the individuals of a species, all of which equally undergo those changes which new conditions may impose upon them. In this respect a new species has a multiple origin, but this in a sense very different from that which was upheld by L. Agassiz. As Murray himself puts it: "To my multiple origin, communication and direct derivation is essential. The species is compounded of many influences brought together through many individuals, and distilled by Nature into one species; and, being once established it may roam and spread wherever it finds the conditions of life not materially different from those of its original centre." (Murray, "The Geographical Distribution of Mammals", page 14. London, 1866.) This declaration fairly agrees with more modern views, and it must be borne in mind that the application of the single-centre principle to the genera, families and larger groups in the search for descent inevitably leads to one creative centre for the whole animal kingdom, a condition as unwarrantable as the myth of Adam and Eve being the first representatives of Mankind.

It looks as if it had required almost ten years for "The Origin of Species" to show its full effect, since the year 1868 marks the publication of Haeckel's "Naturliche Schoepfungsgeschichte" in addition to other great works. The terms "Oecology" (the relation of organisms to their environment) and "Chorology" (their distribution in space) had been given us in his "Generelle Morphologie" in 1866. The fourteenth chapter of the "History of Creation" is devoted to the distribution of organisms, their chorology, with the emphatic assertion that "not until Darwin can chorology be spoken of as a separate science, since he supplied the acting causes for the elucidation of the hitherto accumulated mass of facts." A map (a "hypothetical sketch") shows the monophyletic origin and the routes of distribution of Man.

Natural Selection may be all-mighty, all-sufficient, but it requires time, so much that the countless aeons required for the evolution of the present fauna were soon felt to be one of the most serious drawbacks of the theory. Therefore every help to ease and shorten this process should have been welcomed. In 1868 M. Wagner (The first to formulate clearly the fundamental idea of a theory of migration and its importance in the origin of new species was L. von Buch, who in his "Physikalische Beschreibung der Canarischen Inseln", written in 1825, wrote as follows: "Upon the continents the individuals of the genera by spreading far, form, through differences of the locality, food and soil, varieties which finally become constant as new species, since owing to the distances they could never be crossed with other varieties and thus be brought back to the main type. Next they may again, perhaps upon different roads, return to the old home where they find the old type likewise changed, both having become so different that they can interbreed no longer. Not so upon islands, where the individuals shut up in narrow valleys or within narrow districts, can always meet one another and thereby destroy every new attempt towards the fixing of a new variety." Clearly von Buch explains here why island types remain fixed, and why these types themselves have become so different from their continental congeners.—Actually von Buch is aware of a most important point, the difference in the process of development which exists between a new species b, which is the result of an ancestral species a having itself changed into b and thereby vanished itself, and a new species c which arose through separation out of the same ancestral a, which itself persists as such unaltered. Von Buch's prophetic view seems to have escaped Lyell's and even Wagner's notice.) came to the rescue with his "Darwin'sche Theorie und das Migrations-Gesetz der Organismen". (Leipzig, 1868.) He shows that migration, i.e. change of locality, implies new environmental conditions (never mind whether these be new stimuli to variation, or only acting as their selectors or censors), and moreover secures separation from the original stock and thus eliminates or lessens the reactionary dangers of panmixia. Darwin accepted Wagner's theory as "advantageous." Through the heated polemics of the more ardent selectionists Wagner's theory came to grow into an alternative instead of a help to the theory of selectional evolution. Separation is now rightly considered a most important factor by modern students of geographical distribution.

For the same year, 1868, we have to mention Huxley, whose Arctogaea and Notogaea are nothing less than the reconstructed main masses of land of the Mesozoic period. Beyond doubt the configuration of land at that remote period has left recognisable traces in the present continents, but whether they can account for the distribution of such a much later group as the Gallinaceous birds is more than questionable. In any case he took for his text a large natural group of birds, cosmopolitan as a whole, but with a striking distribution. The Peristeropodes, or pigeon-footed division, are restricted to the Australian and Neotropical regions, in distinction to the Alectoropodes (with the hallux inserted at a level above the front toes) which inhabit the whole of the Arctogaea, only a few members having spread into the South World. Further, as Asia alone has its Pheasants and allies, so is Africa characterised by its Guinea-fowls and relations, America has the Turkey as an endemic genus, and the Grouse tribe in a wider sense has its centre in the holarctic region: a splendid object lesson of descent, world-wide spreading and subsequent differentiation. Huxley, by the way, was the first—at least in private talk—to state that it will be for the morphologist, the well-trained anatomist, to give the casting vote in questions of geographical distribution, since he alone can determine whether we have to deal with homologous, or analogous, convergent, representative forms.

It seems late to introduce Wallace's name in 1876, the year of the publication of his standard work. ("The Geographical Distribution of Animals", 2 vols. London, 1876.) We cannot do better than quote the author's own words, expressing the hope that his "book should bear a similar relation to the eleventh and twelfth chapters of the "Origin of Species" as Darwin's "Animals and Plants under Domestication" does to the first chapter of that work," and to add that he has amply succeeded. Pleading for a few primary centres he accepts Sclater's six regions and does not follow Huxley's courageous changes which Sclater himself had accepted in 1874. Holding the view of the permanence of the oceans he accounts for the colonisation of outlying islands by further elaborating the views of Lyell and Darwin, especially in his fascinating "Island Life", with remarkable chapters on the Ice Age, Climate and Time and other fundamental factors. His method of arriving at the degree of relationship of the faunas of the various regions is eminently statistical. Long lists of genera determine by their numbers the affinity and hence the source of colonisation. In order to make sure of his material he performed the laborious task of evolving a new classification of the host of Passerine birds. This statistical method has been followed by many authors, who, relying more upon quantity than quality, have obscured the fact that the key to the present distribution lies in the past changes of the earth's surface. However, with Wallace begins the modern study of the geographical distribution of animals and the sudden interest taken in this subject by an ever widening circle of enthusiasts far beyond the professional brotherhood.

A considerable literature has since grown up, almost bewildering in its range, diversity of aims and style of procedure. It is a chaos, with many paths leading into the maze, but as yet very few take us to a position commanding a view of the whole intricate terrain with its impenetrable tangle and pitfalls.

One line of research, not initiated but greatly influenced by Wallace's works, became so prominent as to almost constitute a period which may be characterised as that of the search by specialists for either the justification or the amending of his regions. As class after class of animals was brought up to reveal the secret of the true regions, some authors saw in their different results nothing but the faultiness of previously established regions; others looked upon eventual agreements as their final corroboration, especially when for instance such diverse groups as mammals and scorpions could, with some ingenuity, be made to harmonise. But the obvious result of all these efforts was the growing knowledge that almost every class seemed to follow principles of its own. The regions tallied neither in extent nor in numbers, although most of them gravitated more and more towards three centres, namely Australia, South America and the rest of the world. Still zoologists persisted in the search, and the various modes and capabilities of dispersal of the respective groups were thought sufficient explanation of the divergent results in trying to bring the mapping of the world under one scheme.

Contemporary literature is full of devices for the mechanical dispersal of animals. Marine currents, warm and cold, were favoured all the more since they showed the probable original homes of the creatures in question. If these could not stand sea-water, they floated upon logs or icebergs, or they were blown across by storms; fishes were lifted over barriers by waterspouts, and there is on record even an hypothetical land tortoise, full of eggs, which colonised an oceanic island after a perilous sea voyage upon a tree trunk. Accidents will happen, and beyond doubt many freaks of discontinuous distribution have to be accounted for by some such means. But whilst sufficient for the scanty settlers of true oceanic islands, they cannot be held seriously to account for the rich fauna of a large continent, over which palaeontology shows us that the immigrants have passed like waves. It should also be borne in mind that there is a great difference between flotsam and jetsam. A current is an extension of the same medium and the animals in it may suffer no change during even a long voyage, since they may be brought from one litoral to another where they will still be in the same or but slightly altered environment. But the jetsam is in the position of a passenger who has been carried off by the wrong train. Almost every year some American land birds arrive at our western coasts and none of them have gained a permanent footing although such visits must have taken place since prehistoric times. It was therefore argued that only those groups of animals should be used for locating and defining regions which were absolutely bound to the soil. This method likewise gave results not reconcilable with each other, even when the distribution of fossils was taken into account, but it pointed to the absolute necessity of searching for former land-connections regardless of their extent and the present depths to which they may have sunk.

That the key to the present distribution lies in the past had been felt long ago, but at last it was appreciated that the various classes of animals and plants have appeared in successive geological epochs and also at many places remote from each other. The key to the distribution of any group lies in the configuration of land and water of that epoch in which it made its first appearance. Although this sounds like a platitude, it has frequently been ignored. If, for argument's sake, Amphibia were evolved somewhere upon the great southern land-mass of Carboniferous times (supposed by some to have stretched from South America across Africa to Australia), the distribution of this developing class must have proceeded upon lines altogether different from that of the mammals which dated perhaps from lower Triassic times, when the old south continental belt was already broken up. The broad lines of this distribution could never coincide with that of the other, older class, no matter whether the original mammalian centre was in the Afro-Indian, Australian, or Brazilian portion. If all the various groups of animals had come into existence at the same time and at the same place, then it would be possible, with sufficient geological data, to construct a map showing the generalised results applicable to the whole animal kingdom. But the premises are wrong. Whatever regions we may seek to establish applicable to all classes, we are necessarily mixing up several principles, namely geological, historical, i.e. evolutionary, with present day statistical facts. We might as well attempt one compound picture representing a chick's growth into an adult bird and a child's growth into manhood.

In short there are no general regions, not even for each class separately, unless this class be one which is confined to a comparatively short geological period. Most of the great classes have far too long a history and have evolved many successive main groups. Let us take the mammals. Marsupials live now in Australia and in both Americas, because they already existed in Mesozoic times; Ungulata existed at one time or other all over the world except in Australia, because they are post-Cretaceous; Insectivores, although as old as any Placentalia, are cosmopolitan excepting South America and Australia; Stags and Bears, as examples of comparatively recent Arctogaeans, are found everywhere with the exception of Ethiopia and Australia. Each of these groups teaches a valuable historical lesson, but when these are combined into the establishment of a few mammalian "realms," they mean nothing but statistical majorities. If there is one at all, Australia is such a realm backed against the rest of the world, but as certainly it is not a mammalian creative centre!

Well then, if the idea of generally applicable regions is a mare's nest, as was the search for the Holy Grail, what is the object of the study of geographical distribution? It is nothing less than the history of the evolution of life in space and time in the widest sense. The attempt to account for the present distribution of any group of organisms involves the aid of every branch of science. It bids fair to become a history of the world. It started in a mild, statistical way, restricting itself to the present fauna and flora and to the present configuration of land and water. Next came Oceanography concerned with the depths of the seas, their currents and temperatures; then enquiries into climatic changes, culminating in irreconcilable astronomical hypotheses as to glacial epochs; theories about changes of the level of the seas, mainly from the point of view of the physicist and astronomer. Then came more and more to the front the importance of the geological record, hand in hand with the palaeontological data and the search for the natural affinities, the genetic system of the organisms. Now and then it almost seems as if the biologists had done their share by supplying the problems and that the physicists and geologists would settle them, but in reality it is not so. The biologists not only set the problems, they alone can check the offered solutions. The mere fact of palms having flourished in Miocene Spitzbergen led to an hypothetical shifting of the axis of the world rather than to the assumption, by way of explanation, that the palms themselves might have changed their nature. One of the most valuable aids in geological research, often the only means for reconstructing the face of the earth in by-gone periods, is afforded by fossils, but only the morphologist can pronounce as to their trustworthiness as witnesses, because of the danger of mistaking analogous for homologous forms. This difficulty applies equally to living groups, and it is so important that a few instances may not be amiss.

There is undeniable similarity between the faunas of Madagascar and South America. This was supported by the Centetidae and Dendrobatidae, two entire "families," as also by other facts. The value of the Insectivores, Solenodon in Cuba, Centetes in Madagascar, has been much lessened by their recognition as an extremely ancient group and as a case of convergence, but if they are no longer put into the same family, this amendment is really to a great extent due to their widely discontinuous distribution. The only systematic difference of the Dendrobatidae from the Ranidae is the absence of teeth, morphologically a very unimportant character, and it is now agreed, on the strength of their distribution, that these little arboreal, conspicuously coloured frogs, Dendrobates in South America, Mantella in Madagascar, do not form a natural group, although a third genus, Cardioglossa in West Africa, seems also to belong to them. If these creatures lived all on the same continent, we should unhesitatingly look upon them as forming a well-defined, natural little group. On the other hand the Aglossa, with their three very divergent genera, namely Pipa in South America, Xenopus and Hymenochirus in Africa, are so well characterised as one ancient group that we use their distribution unhesitatingly as a hint of a former connection between the two continents. We are indeed arguing in vicious circles. The Ratitae as such are absolutely worthless since they are a most heterogeneous assembly, and there are untold groups, of the artificiality of which many a zoo-geographer had not the slightest suspicion when he took his statistical material, the genera and families, from some systematic catalogues or similar lists. A lamentable instance is that of certain flightless Rails, recently extinct or sub-fossil, on the isalnds of Mauritius, Rodriguez and Chatham. Being flightless they have been used in support of a former huge Antarctic continent, instead of ruling them out of court as Rails which, each in its island, have lost the power of flight, a process which must have taken place so recently that it is difficult, upon morphological grounds, to justify their separation into Aphanapteryx in Mauritius, Erythromachus in Rodriguez and Diaphorapteryx on Chatham Island. Morphologically they may well form but one genus, since they have sprung from the same stock and have developed upon the same lines; they are therefore monogenetic: but since we know that they have become what they are independently of each other (now unlike any other Rails), they are polygenetic and therefore could not form one genus in the old Darwinian sense. Further, they are not a case of convergence, since their ancestry is not divergent but leads into the same stratum.

THE RECONSTRUCTION OF THE GEOGRAPHY OF SUCCESSIVE EPOCHS.

A promising method is the study by the specialist of a large, widely distributed group of animals from an evolutionary point of view. Good examples of this method are afforded by A.E. Ortmann's ("The geographical distribution of Freshwater Decapods and its bearing upon ancient geography", "Proc. Amer. Phil. Soc." Vol. 41, 1902.) exhaustive paper and by A.W. Grabau's "Phylogeny of Fusus and its Allies" ("Smithsonian Misc. Coll." 44, 1904.) After many important groups of animals have been treated in this way—as yet sparingly attempted—the results as to hypothetical land-connections etc. are sure to be corrective and supplementary, and their problems will be solved, since they are not imaginary.

The same problems are attacked, in the reverse way, by starting with the whole fauna of a country and thence, so to speak, letting the research radiate. Some groups will be considered as autochthonous, others as immigrants, and the directions followed by them will be inquired into; the search may lead far and in various directions, and by comparison of results, by making compound maps, certain routes will assume definite shape, and if they lead across straits and seas they are warrants to search for land-connections in the past. (A fair sample of this method is C.H. Eigenmann's "The Freshwater Fishes of South and Middle America", "Popular Science Monthly", Vol. 68, 1906.) There are now not a few maps purporting to show the outlines of land and water at various epochs. Many of these attempts do not tally with each other, owing to the lamentable deficiencies of geological and fossil data, but the bolder the hypothetical outlines are drawn, the better, and this is preferable to the insertion of bays and similar detail which give such maps a fallacious look of certainty where none exists. Moreover it must be borne in mind that, when we draw a broad continental belt across an ocean, this belt need never have existed in its entirety at any one time. The features of dispersal, intended to be explained by it, would be accomplished just as well by an unknown number of islands which have joined into larger complexes while elsewhere they subsided again: like pontoon-bridges which may be opened anywhere, or like a series of superimposed dissolving views of land and sea-scapes. Hence the reconstructed maps of Europe, the only continent tolerably known, show a considerable number of islands in puzzling changes, while elsewhere, e.g. in Asia, we have to be satisfied with sweeping generalisations.

At present about half-a-dozen big connections are engaging our attention, leaving as comparatively settled the extent and the duration of such minor "bridges" as that between Africa and Madagascar, Tasmania and Australia, the Antilles and Central America, Europe and North Africa. (Not a few of those who are fascinated by, and satisfied with, the statistical aspect of distribution still have a strong dislike to the use of "bridges" if these lead over deep seas, and they get over present discontinuous occurrences by a former "universal or sub-universal distribution" of their groups.) This is indeed an easy method of cutting the knot, but in reality they shunt the question only a stage or two back, never troubling to explain how their groups managed to attain to that sub-universal range; or do they still suppose that the whole world was originally one paradise where everything lived side by side, until sin and strife and glacial epochs left nothing but scattered survivors?

The permanence of the great ocean-basins had become a dogma since it was found that a universal elevation of the land to the extent of 100 fathoms would produce but little changes, and when it was shown that even the 1000 fathom-line followed the great masses of land rather closely, and still leaving the great basins (although transgression of the sea to the same extent would change the map of the world beyond recognition), by general consent one mile was allowed as the utmost speculative limit of subsidence. Naturally two or three miles, the average depth of the oceans, seems enormous, and yet such a difference in level is as nothing in comparison with the size of the Earth. On a clay model globe ten feet in diameter an ocean bed three miles deep would scarcely be detected, and the highest mountains would be smaller than the unavoidable grains in the glazed surface of our model. There are but few countries which have not be submerged at some time or other.

CONNECTION OF SOUTH EASTERN ASIA WITH AUSTRALIA. Neumayr's Sino-Australian continent during mid-Mesozoic times was probably a much changing Archipelago, with final separations subsequent to the Cretaceous period. Henceforth Australasia was left to its own fate, but for a possible connection with the antarctic continent.

AFRICA, MADAGASCAR, INDIA. The "Lemuria" of Sclater and Haeckel cannot have been more than a broad bridge in Jurassic times; whether it was ever available for the Lemurs themselves must depend upon the time of its duration, the more recent the better, but it is difficult to show that it lasted into the Miocene.

AFRICA AND SOUTH AMERICA. Since the opposite coasts show an entire absence of marine fossils and deposits during the Mesozoic period, whilst further north and south such are known to exist and are mostly identical on either side, Neumayr suggested the existence of a great Afro-Son American mass of land during the Jurassic epoch. Such land is almost a necessity and is supported by many facts; it would easily explain the distribution of numerous groups of terrestrial creatures. Moreover to the north of this hypothetical land, somewhere across from the Antilles and Guiana to North Africa and South Western Europe, existed an almost identical fauna of Corals and Molluscs, indicating either a coast-line or a series of islands interrupted by shallow seas, just as one would expect if, and when, a Brazil-Ethiopian mass of land were breaking up. Lastly from Central America to the Mediterranean stretches one of the Tertiary tectonic lines of the geologists. Here also the great question is how long this continent lasted. Apparently the South Atlantic began to encroach from the south so that by the later Cretaceous epoch the land was reduced to a comparatively narrow Brazil-West Africa, remnants of which persisted certainly into the early Tertiary, until the South Atlantic joined across the equator with the Atlantic portion of the "Thetys," leaving what remained of South America isolated from the rest of the world.

ANTARCTIC CONNECTIONS. Patagonia and Argentina seem to have joined Antartica during the Cretaceous epoch, and this South Georgian bridge had broken down again by mid-Tertiary times when South America became consolidated. The Antarctic continent, presuming that it existed, seems also to have been joined, by way of Tasmania, with Australia, also during the Cretaceous epoch, and it is assumed that the great Australia-Antarctic-Patagonian land was severed first to the south of Tasmania and then at the South Georgian bridge. No connection, and this is important, is indicated between Antarctica and either Africa or Madagascar.

So far we have followed what may be called the vicissitudes of the great Permo-Carboniferous Gondwana land in its fullest imaginary extent, an enormous equatorial and south temperate belt from South America to Africa, South India and Australia, which seems to have provided the foundation of the present Southern continents, two of which temporarily joined Antarctica, of which however we know nothing except that it exists now.

Let us next consider the Arctic and periarctic lands. Unfortunately very little is known about the region within the arctic circle. If it was all land, or more likely great changing archipelagoes, faunistic exchange between North America, Europe and Siberia would present no difficulties, but there is one connection which engages much attention, namely a land where now lies the North temperate and Northern part of the Atlantic ocean. How far south did it ever extend and what is the latest date of a direct practicable communication, say from North Western Europe to Greenland? Connections, perhaps often interrupted, e.g. between Greenland and Labrador, at another time between Greenland and Scandinavia, seem to have existed at least since the Permo-Carboniferous epoch. If they existed also in late Cretaceous and in Tertiary times, they would of course easily explain exchanges which we know to have repeatedly taken place between America and Europe, but they are not proved thereby, since most of these exchanges can almost as easily have occurred across the polar regions, and others still more easily by repeated junction of Siberia with Alaska.

Let us now describe a hypothetical case based on the supposition of connecting bridges. Not to work in a circle, we select an important group which has not served as a basis for the reconstruction of bridges; and it must be a group which we feel justified in assuming to be old enough to have availed itself of ancient land-connections.

The occurrence of one species of Peripatus in the whole of Australia, Tasmania and New Zealand (the latter being joined to Australia by way of New Britain in Cretaceous times but not later) puts the genus back into this epoch, no unsatisfactory assumption to the morphologist. The apparent absence of Peripatus in Madagascar indicates that it did not come from the east into Africa, that it was neither Afro-Indian, nor Afro-Australian; nor can it have started in South America. We therefore assume as its creative centre Australia or Malaya in the Cretaceous epoch, whence its occurrence in Sumatra, Malay Peninsula, New Britain, New Zealand and Australia is easily explained. Then extension across Antarctica to Patagonia and Chile, whence it could spread into the rest of South America as this became consolidated in early Tertiary times. For getting to the Antilles and into Mexico it would have to wait until the Miocene, but long before that time it could arrive in Africa, there surviving as a Congolese and a Cape species. This story is unsupported by a single fossil. Peripatus may have been "sub-universal" all over greater Gondwana land in Carboniferous times, and then its absence from Madagascar would be difficult to explain, but the migrations suggested above amount to little considering that the distance from Tasmania to South America could be covered in far less time than that represented by the whole of the Eocene epoch alone.

There is yet another field, essentially the domain of geographical distribution, the cultivation of which promises fair to throw much light upon Nature's way of making species. This is the study of the organisms with regard to their environment. Instead of revealing pedigrees or of showing how and when the creatures got to a certain locality, it investigates how they behaved to meet the ever changing conditions of their habitats. There is a facies, characteristic of, and often peculiar to, the fauna of tropical moist forests, another of deserts, of high mountains, of underground life and so forth; these same facies are stamped upon whole associations of animals and plants, although these may be—and in widely separated countries generally are—drawn from totally different families of their respective orders. It does not go to the root of the matter to say that these facies have been brought about by the extermination of all the others which did not happen to fit into their particular environment. One might almost say that tropical moist forests must have arboreal frogs and that these are made out of whatever suitable material happened to be available; in Australia and South America Hylidae, in Africa Ranidae, since there Hylas are absent. The deserts must have lizards capable of standing the glare, the great changes of temperature, of running over or burrowing into the loose sand. When as in America Iguanids are available, some of these are thus modified, while in Africa and Asia the Agamids are drawn upon. Both in the Damara and in the Transcaspian deserts, a Gecko has been turned into a runner upon sand!

We cannot assume that at various epochs deserts, and at others moist forests were continuous all over the world. The different facies and associations were developed at various times and places. Are we to suppose that, wherever tropical forests came into existence, amongst the stock of humivagous lizards were always some which presented those nascent variations which made them keep step with the similarly nascent forests, the overwhelming rest being eliminated? This principle would imply that the same stratum of lizards always had variations ready to fit any changed environment, forests and deserts, rocks and swamps. The study of Ecology indicates a different procedure, a great, almost boundless plasticity of the organism, not in the sense of an exuberant moulding force, but of a readiness to be moulded, and of this the "variations" are the visible outcome. In most cases identical facies are produced by heterogeneous convergences and these may seem to be but superficial, affecting only what some authors are pleased to call the physiological characters; but environment presumably affects first those parts by which the organism comes into contact with it most directly, and if the internal structures remain unchanged, it is not because these are less easily modified but because they are not directly affected. When they are affected, they too change deeply enough.

That the plasticity should react so quickly—indeed this very quickness seems to have initiated our mistaking the variations called forth for something performed—and to the point, is itself the outcome of the long training which protoplasm has undergone since its creation.

In Nature's workshop he does not succeed who has ready an arsenal of tools for every conceivable emergency, but he who can make a tool at the spur of the moment. The ordeal of the practical test is Charles Darwin's glorious conception of Natural Selection.



XVIII. DARWIN AND GEOLOGY. By J.W. Judd, C.B., LL.D., F.R.S.

(Mr Francis Darwin has related how his father occasionally came up from Down to spend a few days with his brother Erasmus in London, and, after his brother's death, with his daughter, Mrs Litchfield. On these occasions, it was his habit to arrange meetings with Huxley, to talk over zoological questions, with Hooker, to discuss botanical problems, and with Lyell to hold conversations on geology. After the death of Lyell, Darwin, knowing my close intimacy with his friend during his later years, used to ask me to meet him when he came to town, and "talk geology." The "talks" took place sometimes at Jermyn Street Museum, at other times in the Royal College of Science, South Kensington; but more frequently, after having lunch with him, at his brother's or his daughter's house. On several occasions, however, I had the pleasure of visiting him at Down. In the postscript of a letter (of April 15, 1880) arranging one of these visits, he writes: "Since poor, dear Lyell's death, I rarely have the pleasure of geological talk with anyone.")

In one of the very interesting conversations which I had with Charles Darwin during the last seven years of his life, he asked me in a very pointed manner if I were able to recall the circumstances, accidental or otherwise, which had led me to devote myself to geological studies. He informed me that he was making similar inquiries of other friends, and I gathered from what he said that he contemplated at that time a study of the causes producing SCIENTIFIC BIAS in individual minds. I have no means of knowing how far this project ever assumed anything like concrete form, but certain it is that Darwin himself often indulged in the processes of mental introspection and analysis; and he has thus fortunately left us—in his fragments of autobiography and in his correspondence—the materials from which may be reconstructed a fairly complete history of his own mental development.

There are two perfectly distinct inquiries which we have to undertake in connection with the development of Darwin's ideas on the subject of evolution:

FIRST. How, when, and under what conditions was Darwin led to a conviction that species were not immutable, but were derived from pre-existing forms?

SECONDLY. By what lines of reasoning and research was he brought to regard "natural selection" as a vera causa in the process of evolution?

It is the first of these inquiries which specially interests the geologist; though geology undoubtedly played a part—and by no means an insignificant part—in respect to the second inquiry.

When, indeed, the history comes to be written of that great revolution of thought in the nineteenth century, by which the doctrine of evolution, from being the dream of poets and visionaries, gradually grew to be the accepted creed of naturalists, the paramount influence exerted by the infant science of geology—and especially that resulting from the publication of Lyell's epoch-making work, the "Principles of Geology"—cannot fail to be regarded as one of the leading factors. Herbert Spencer in his "Autobiography" bears testimony to the effect produced on his mind by the recently published "Principles", when, at the age of twenty, he had already begun to speculate on the subject of evolution (Herbert Spencer's "Autobiography", London, 1904, Vol. I. pages 175-177.); and Alfred Russel Wallace is scarcely less emphatic concerning the part played by Lyell's teaching in his scientific education. (See "My Life; a record of Events and Opinions", London, 1905, Vol. I. page 355, etc. Also his review of Lyell's "Principles" in "Quarterly Review" (Vol. 126), 1869, pages 359-394. See also "The Darwin-Wallace Celebration by the Linnean Society" (1909), page 118.) Huxley wrote in 1887 "I owe more than I can tell to the careful study of the "Principles of Geology" in my young days." ("Science and Pseudo Science"; "Collected Essays", London, 1902, Vol. V. page 101.) As for Charles Darwin, he never tired—either in his published writings, his private correspondence or his most intimate conversations—of ascribing the awakening of his enthusiasm and the direction of his energies towards the elucidation of the problem of development to the "Principles of Geology" and the personal influence of its author. Huxley has well expressed what the author of the "Origin of Species" so constantly insisted upon, in the statements "Darwin's greatest work is the outcome of the unflinching application to Biology of the leading idea and the method applied in the "Principles" to Geology ("Proc. Roy. Soc." Vol. XLIV. (1888), page viii.; "Collected Essays" II. page 268, 1902.), and "Lyell, for others, as for myself, was the chief agent in smoothing the road for Darwin." ("Life and Letters of Charles Darwin" II. page 190.)

We propose therefore to consider, first, what Darwin owed to geology and its cultivators, and in the second place how he was able in the end so fully to pay a great debt which he never failed to acknowledge. Thanks to the invaluable materials contained in the "Life and Letters of Charles Darwin" (3 vols.) published by Mr Francis Darwin in 1887; and to "More Letters of Charles Darwin" (2 vols.) issued by the same author, in conjunction with Professor A.C. Seward, in 1903, we are permitted to follow the various movements in Darwin's mind, and are able to record the story almost entirely in his own words. (The first of these works is indicated in the following pages by the letters "L.L."; the second by "M.L.")

From the point of view of the geologist, Darwin's life naturally divides itself into four periods. In the first, covering twenty-two years, various influences were at work militating, now for and now against, his adoption of a geological career; in the second period—the five memorable years of the voyage of the "Beagle"—the ardent sportsman with some natural-history tastes, gradually became the most enthusiastic and enlightened of geologists; in the third period, lasting ten years, the valuable geological recruit devoted nearly all his energies and time to geological study and discussion and to preparing for publication the numerous observations made by him during the voyage; the fourth period, which covers the latter half of his life, found Darwin gradually drawn more and more from geological to biological studies, though always retaining the deepest interest in the progress and fortunes of his "old love." But geologists gladly recognise the fact that Darwin immeasurably better served their science by this biological work, than he could possibly have done by confining himself to purely geological questions.

From his earliest childhood, Darwin was a collector, though up to the time when, at eight years of age, he went to a preparatory school, seals, franks and similar trifles appear to have been the only objects of his quest. But a stone, which one of his schoolfellows at that time gave to him, seems to have attracted his attention and set him seeking for pebbles and minerals; as the result of this newly acquired taste, he says (writing in 1838) "I distinctly recollect the desire I had of being able to know something about every pebble in front of the hall door—it was my earliest and only geological aspiration at that time." ("M.L." I. page 3.) He further suspects that while at Mr Case's school "I do not remember any mental pursuits except those of collecting stones," etc... "I was born a naturalist." ("M.L." I. page 4.)

The court-yard in front of the hall door at the Mount House, Darwin's birthplace and the home of his childhood, is surrounded by beds or rockeries on which lie a number of pebbles. Some of these pebbles (in quite recent times as I am informed) have been collected to form a "cobbled" space in front of the gate in the outer wall, which fronts the hall door; and a similar "cobbled area," there is reason to believe, may have existed in Darwin's childhood before the door itself. The pebbles, which were obtained from a neighbouring gravel-pit, being derived from the glacial drift, exhibit very striking differences in colour and form. It was probably this circumstance which awakened in the child his love of observation and speculation. It is certainly remarkable that "aspirations" of the kind should have arisen in the mind of a child of 9 or 10!

When he went to Shrewsbury School, he relates "I continued collecting minerals with much zeal, but quite unscientifically,—all that I cared about was a new-NAMED mineral, and I hardly attempted to classify them." ("L.L." I. page 34.)

There has stood from very early times in Darwin's native town of Shrewsbury, a very notable boulder which has probably marked a boundary and is known as the "Bell-stone"—giving its name to a house and street. Darwin tells us in his "Autobiography" that while he was at Shrewsbury School at the age of 13 or 14 "an old Mr Cotton in Shropshire, who knew a good deal about rocks" pointed out to me "... the 'bell-stone'; he told me that there was no rock of the same kind nearer than Cumberland or Scotland, and he solemnly assured me that the world would come to an end before anyone would be able to explain how this stone came where it now lay"! Darwin adds "This produced a deep impression on me, and I meditated over this wonderful stone." ("L.L." I. page 41.)

The "bell-stone" has now, owing to the necessities of building, been removed a short distance from its original site, and is carefully preserved within the walls of a bank. It is a block of irregular shape 3 feet long and 2 feet wide, and about 1 foot thick, weighing probably not less than one-third of a ton. By the courtesy of the directors of the National Provincial Bank of England, I have been able to make a minute examination of it, and Professors Bonney and Watts, with Mr Harker and Mr Fearnsides have given me their valuable assistance. The rock is a much altered andesite and was probably derived from the Arenig district in North Wales, or possibly from a point nearer the Welsh Border. (I am greatly indebted to the Managers of the Bank at Shrewsbury for kind assistance in the examination of this interesting memorial: and Mr H.T. Beddoes, the Curator of the Shrewsbury Museum, has given me some archaeological information concerning the stone. Mr Richard Cotton was a good local naturalist, a Fellow both of the Geological and Linnean Societies; and to the officers of these societies I am indebted for information concerning him. He died in 1839, and although he does not appear to have published any scientific papers, he did far more for science by influencing the career of the school boy!) It was of course brought to where Shrewsbury now stands by the agency of a glacier—as Darwin afterwards learnt.

We can well believe from the perusal of these reminiscences that, at this time, Darwin's mind was, as he himself says, "prepared for a philosophical treatment of the subject" of Geology. ("L.L." I. page 41.) When at the age of 16, however, he was entered as a medical student at Edinburgh University, he not only did not get any encouragement of his scientific tastes, but was positively repelled by the ordinary instruction given there. Dr Hope's lectures on Chemistry, it is true, interested the boy, who with his brother Erasmus had made a laboratory in the toolhouse, and was nicknamed "Gas" by his schoolfellows, while undergoing solemn and public reprimand from Dr Butler at Shrewsbury School for thus wasting his time. ("L.L." I. page 35.) But most of the other Edinburgh lectures were "intolerably dull," "as dull as the professors" themselves, "something fearful to remember." In after life the memory of these lectures was like a nightmare to him. He speaks in 1840 of Jameson's lectures as something "I... for my sins experienced!" ("L.L." I. page 340.) Darwin especially signalises these lectures on Geology and Zoology, which he attended in his second year, as being worst of all "incredibly dull. The sole effect they produced on me was the determination never so long as I lived to read a book on Geology, or in any way to study the science!" ("L.L." I. page 41.)

The misfortune was that Edinburgh at that time had become the cockpit in which the barren conflict between "Neptunism" and "Plutonism" was being waged with blind fury and theological bitterness. Jameson and his pupils, on the one hand, and the friends and disciples of Hutton, on the other, went to the wildest extremes in opposing each other's peculiar tenets. Darwin tells us that he actually heard Jameson "in a field lecture at Salisbury Craigs, discoursing on a trap-dyke, with amygdaloidal margins and the strata indurated on each side, with volcanic rocks all around us, say that it was a fissure filled with sediment from above, adding with a sneer that there were men who maintained that it had been injected from beneath in a molten condition." ("L.L." I. pages 41-42.) "When I think of this lecture," added Darwin, "I do not wonder that I determined never to attend to Geology." (This was written in 1876 and Darwin had in the summer of 1839 revisited and carefully studied the locality ("L.L." I. page 290.) It is probable that most of Jameson's teaching was of the same controversial and unilluminating character as this field-lecture at Salisbury Craigs.

There can be no doubt that, while at Edinburgh, Darwin must have become acquainted with the doctrines of the Huttonian School. Though so young, he mixed freely with the scientific society of the city, Macgillivray, Grant, Leonard Horner, Coldstream, Ainsworth and others being among his acquaintances, while he attended and even read papers at the local scientific societies. It is to be feared, however, that what Darwin would hear most of, as characteristic of the Huttonian teaching, would be assertions that chalk-flints were intrusions of molten silica, that fossil wood and other petrifactions had been impregnated with fused materials, that heat—but never water—was always the agent by which the induration and crystallisation of rock-materials (even siliceous conglomerate, limestone and rock-salt) had been effected! These extravagant "anti-Wernerian" views the young student might well regard as not one whit less absurd and repellant than the doctrine of the "aqueous precipitation" of basalt. There is no evidence that Darwin, even if he ever heard of them, was in any way impressed, in his early career, by the suggestive passages in Hutton and Playfair, to which Lyell afterwards called attention, and which foreshadowed the main principles of Uniformitarianism.

As a matter of fact, I believe that the influence of Hutton and Playfair in the development of a philosophical theory of geology has been very greatly exaggerated by later writers on the subject. Just as Wells and Matthew anticipated the views of Darwin on Natural Selection, but without producing any real influence on the course of biological thought, so Hutton and Playfair adumbrated doctrines which only became the basis of vivifying theory in the hands of Lyell. Alfred Russel Wallace has very justly remarked that when Lyell wrote the "Principles of Geology", "the doctrines of Hutton and Playfair, so much in advance of their age, seemed to be utterly forgotten." ("Quarterly Review", Vol. CXXVI. (1869), page 363.) In proof of this it is only necessary to point to the works of the great masters of English geology, who preceded Lyell, in which the works of Hutton and his followers are scarcely ever mentioned. This is true even of the "Researches in Theoretical Geology" and the other works of the sagacious De la Beche. (Of the strength and persistence of the prejudice felt against Lyell's views by his contemporaries, I had a striking illustration some little time after Lyell's death. One of the old geologists who in the early years of the century had done really good work in connection with the Geological Society expressed a hope that I was not "one of those who had been carried away by poor Lyell's fads." My surprise was indeed great when further conversation showed me that the whole of the "Principles" were included in the "fads"!) Darwin himself possessed a copy of Playfair's "Illustrations of the Huttonian Theory", and occasionally quotes it; but I have met with only one reference to Hutton, and that a somewhat enigmatical one, in all Darwin's writings. In a letter to Lyell in 1841, when his mind was much exercised concerning glacial questions, he says "What a grand new feature all this ice work is in Geology! How old Hutton would have stared!" ("M.L." II. page 149.)

As a consequence of the influences brought to bear on his mind during his two years' residence in Edinburgh, Darwin, who had entered that University with strong geological aspirations, left it and proceeded to Cambridge with a pronounced distaste for the whole subject. The result of this was that, during his career as an under-graduate, he neglected all the opportunities for geological study. During that important period of life, when he was between eighteen and twenty years of age, Darwin spent his time in riding, shooting and beetle-hunting, pursuits which were undoubtedly an admirable preparation for his future work as an explorer; but in none of his letters of this period does he even mention geology. He says, however, "I was so sickened with lectures at Edinburgh that I did not even attend Sedgwick's eloquent and interesting lectures." ("L.L." I. page 48.)

It was only after passing his examination, and when he went up to spend two extra terms at Cambridge, that geology again began to attract his attention. The reading of Sir John Herschel's "Introduction to the Study of Natural Philosophy", and of Humboldt's "Personal Narrative", a copy of which last had been given to him by his good friend and mentor Henslow, roused his dormant enthusiasm for science, and awakened in his mind a passionate desire for travel. And it was from Henslow, whom he had accompanied in his excursions, but without imbibing any marked taste, at that time, for botany, that the advice came to think of and to "begin the study of geology." ("L.L." I. page 56.) This was in 1831, and in the summer vacation of that year we find him back again at Shrewsbury "working like a tiger" at geology and endeavouring to make a map and section of Shropshire—work which he says was not "as easy as I expected." ("L.L." I. page 189.) No better field for geological studies could possibly be found than Darwin's native county.

Writing to Henslow at this time, and referring to a form of the instrument devised by his friend, Darwin says: "I am very glad to say I think the clinometer will answer admirably. I put all the tables in my bedroom at every conceivable angle and direction. I will venture to say that I have measured them as accurately as any geologist going could do." But he adds: "I have been working at so many things that I have not got on much with geology. I suspect the first expedition I take, clinometer and hammer in hand, will send me back very little wiser and a good deal more puzzled than when I started." ("L.L." I. page 189.) Valuable aid was, however, at hand, for at this time Sedgwick, to whom Darwin had been introduced by the ever-helpful Henslow, was making one of his expeditions into Wales, and consented to accept the young student as his companion during the geological tour. ("L.L." I. page 56.) We find Darwin looking forward to this privilege with the keenest interest. ("L.L." I. page 189.)

When at the beginning of August (1831), Sedgwick arrived at his father's house in Shrewsbury, where he spent a night, Darwin began to receive his first and only instruction as a field-geologist. The journey they took together led them through Llangollen, Conway, Bangor, and Capel Curig, at which latter place they parted after spending many hours in examining the rocks at Cwm Idwal with extreme care, seeking for fossils but without success. Sedgwick's mode of instruction was admirable—he from time to time sent the pupil off on a line parallel to his own, "telling me to bring back specimens of the rocks and to mark the stratification on a map." ("L.L." I. page 57.) On his return to Shrewsbury, Darwin wrote to Henslow, "My trip with Sedgwick answered most perfectly," ("L.L." I. page 195.), and in the following year he wrote again from South America to the same friend, "Tell Professor Sedgwick he does not know how much I am indebted to him for the Welsh expedition; it has given me an interest in Geology which I would not give up for any consideration. I do not think I ever spent a more delightful three weeks than pounding the north-west mountains." ("L.L." I. pages 237-8.)

It would be a mistake, however, to suppose that at this time Darwin had acquired anything like the affection for geological study, which he afterwards developed. After parting with Sedgwick, he walked in a straight line by compass and map across the mountains to Barmouth to visit a reading party there, but taking care to return to Shropshire before September 1st, in order to be ready for the shooting. For as he candidly tells us, "I should have thought myself mad to give up the first days of partridge-shooting for geology or any other science!" ("L.L." I. page 58.)

Any regret we may be disposed to feel that Darwin did not use his opportunities at Edinburgh and Cambridge to obtain systematic and practical instruction in mineralogy and geology, will be mitigated, however, when we reflect on the danger which he would run of being indoctrinated with the crude "catastrophic" views of geology, which were at that time prevalent in all the centres of learning.

Writing to Henslow in the summer of 1831, Darwin says "As yet I have only indulged in hypotheses, but they are such powerful ones that I suppose, if they were put into action but for one day, the world would come to an end." ("L.L." I. page 189.)

May we not read in this passage an indication that the self-taught geologist had, even at this early stage, begun to feel a distrust for the prevalent catastrophism, and that his mind was becoming a field in which the seeds which Lyell was afterwards to sow would "fall on good ground"?

The second period of Darwin's geological career—the five years spent by him on board the "Beagle"—was the one in which by far the most important stage in his mental development was accomplished. He left England a healthy, vigorous and enthusiastic collector; he returned five years later with unique experiences, the germs of great ideas, and a knowledge which placed him at once in the foremost ranks of the geologists of that day. Huxley has well said that "Darwin found on board the "Beagle" that which neither the pedagogues of Shrewsbury, nor the professoriate of Edinburgh, nor the tutors of Cambridge had managed to give him." ("Proc. Roy. Soc." Vol. XLIV. (1888), page IX.) Darwin himself wrote, referring to the date at which the voyage was expected to begin: "My second life will then commence, and it shall be as a birthday for the rest of my life." ("L.L." I. page 214.); and looking back on the voyage after forty years, he wrote; "The voyage of the 'Beagle' has been by far the most important event in my life, and has determined my whole career;... I have always felt that I owe to the voyage the first real training or education of my mind; I was led to attend closely to several branches of natural history, and thus my powers of observation were improved, though they were always fairly developed." ("L.L." I. page 61.)

Referring to these general studies in natural history, however, Darwin adds a very significant remark: "The investigation of the geology of the places visited was far more important, as reasoning here comes into play. On first examining a new district nothing can appear more hopeless than the chaos of rocks; but by recording the stratification and nature of the rocks and fossils at many points, always reasoning and predicting what will be found elsewhere, light soon begins to dawn on the district, and the structure of the whole becomes more or less intelligible." ("L.L." I. page 62.)

The famous voyage began amid doubts, discouragements and disappointments. Fearful of heart-disease, sad at parting from home and friends, depressed by sea-sickness, the young explorer, after being twice driven back by baffling winds, reached the great object of his ambition, the island of Teneriffe, only to find that, owing to quarantine regulations, landing was out of the question.

But soon this inauspicious opening of the voyage was forgotten. Henslow had advised his pupil to take with him the first volume of Lyell's "Principles of Geology", then just published—but cautioned him (as nearly all the leaders in geological science at that day would certainly have done) "on no account to accept the views therein advocated." ("L.L." I. page 73.) It is probable that the days of waiting, discomfort and sea-sickness at the beginning of the voyage were relieved by the reading of this volume. For he says that when he landed, three weeks after setting sail from Plymouth, in St Jago, the largest of the Cape de Verde Islands, the volume had already been "studied attentively; and the book was of the highest service to me in many ways... " His first original geological work, he declares, "showed me clearly the wonderful superiority of Lyell's manner of treating geology, compared with that of any other author, whose works I had with me or ever afterwards read." ("L.L." I. page 62.)

At St Jago Darwin first experienced the joy of making new discoveries, and his delight was unbounded. Writing to his father he says, "Geologising in a volcanic country is most delightful; besides the interest attached to itself, it leads you into most beautiful and retired spots." ("L.L." I. page 228.) To Henslow he wrote of St Jago: "Here we spent three most delightful weeks... St Jago is singularly barren, and produces few plants or insects, so that my hammer was my usual companion, and in its company most delightful hours I spent." "The geology was pre-eminently interesting, and I believe quite new; there are some facts on a large scale of upraised coast (which is an excellent epoch for all the volcanic rocks to date from), that would interest Mr Lyell." ("L.L." I. page 235.) After more than forty years the memory of this, his first geological work, seems as fresh as ever, and he wrote in 1876, "The geology of St Jago is very striking, yet simple: a stream of lava formerly flowed over the bed of the sea, formed of triturated recent shells and corals, which it has baked into a hard white rock. Since then the whole island has been upheaved. But the line of white rock revealed to me a new and important fact, namely, that there had been afterwards subsidence round the craters, which had since been in action, and had poured forth lava." ("L.L." I. page 65.)

It was at this time, probably, that Darwin made his first attempt at drawing a sketch-map and section to illustrate the observations he had made (see his "Volcanic Islands", pages 1 and 9). His first important geological discovery, that of the subsidence of strata around volcanic vents (which has since been confirmed by Mr Heaphy in New Zealand and other authors) awakened an intense enthusiasm, and he writes: "It then first dawned on me that I might perhaps write a book on the geology of the various countries visited, and this made me thrill with delight. That was a memorable hour to me, and how distinctly I can call to mind the low cliff of lava beneath which I rested, with the sun glaring hot, a few strange desert plants growing near, and with living corals in the tidal pools at my feet." ("L.L." I. page 66.)

But it was when the "Beagle", after touching at St Paul's rock and Tristan d'Acunha (for a sufficient time only to collect specimens), reached the shores of South America, that Darwin's real work began; and he was able, while the marine surveys were in progress, to make many extensive journeys on land. His letters at this time show that geology had become his chief delight, and such exclamations as "Geology carries the day," "I find in Geology a never failing interest," etc. abound in his correspondence.

Darwin's time was divided between the study of the great deposits of red mud—the Pampean formation—with its interesting fossil bones and shells affording proofs of slow and constant movements of the land, and the underlying masses of metamorphic and plutonic rocks. Writing to Henslow in March, 1834, he says: "I am quite charmed with Geology, but, like the wise animal between two bundles of hay, I do not know which to like best; the old crystalline groups of rocks, or the softer and fossiliferous beds. When puzzling about stratification, etc., I feel inclined to cry 'a fig for your big oysters, and your bigger megatheriums.' But then when digging out some fine bones, I wonder how any man can tire his arms with hammering granite." ("L.L." I. page 249.) We are told by Darwin that he loved to reason about and attempt to predict the nature of the rocks in each new district before he arrived at it.

This love of guessing as to the geology of a district he was about to visit is amusingly expressed by him in a letter (of May, 1832) to his cousin and old college-friend, Fox. After alluding to the beetles he had been collecting—a taste his friend had in common with himself—he writes of geology that "It is like the pleasure of gambling. Speculating on first arriving, what the rocks may be, I often mentally cry out 3 to 1 tertiary against primitive; but the latter have hitherto won all the bets." ("L.L." I. page 233.)

Not the least important of the educational results of the voyage to Darwin was the acquirement by him of those habits of industry and method which enabled him in after life to accomplish so much—in spite of constant failures of health. From the outset, he daily undertook and resolutely accomplished, in spite of sea-sickness and other distractions, four important tasks. In the first place he regularly wrote up the pages of his Journal, in which, paying great attention to literary style and composition, he recorded only matters that would be of general interest, such as remarks on scenery and vegetation, on the peculiarities and habits of animals, and on the characters, avocations and political institutions of the various races of men with whom he was brought in contact. It was the freshness of these observations that gave his "Narrative" so much charm. Only in those cases in which his ideas had become fully crystallised, did he attempt to deal with scientific matters in this journal. His second task was to write in voluminous note-books facts concerning animals and plants, collected on sea or land, which could not be well made out from specimens preserved in spirit; but he tells us that, owing to want of skill in dissecting and drawing, much of the time spent in this work was entirely thrown away, "a great pile of MS. which I made during the voyage has proved almost useless." ("L.L." I. page 62.) Huxley confirmed this judgment on his biological work, declaring that "all his zeal and industry resulted, for the most part, in a vast accumulation of useless manuscript." ("Proc. Roy. Soc." Vol. XLIV. (1888), page IX.) Darwin's third task was of a very different character and of infinitely greater value. It consisted in writing notes of his journeys on land—the notes being devoted to the geology of the districts visited by him. These formed the basis, not only of a number of geological papers published on his return, but also of the three important volumes forming "The Geology of the voyage of the 'Beagle'". On July 24th, 1834, when little more than half of the voyage had been completed, Darwin wrote to Henslow, "My notes are becoming bulky. I have about 600 small quarto pages full; about half of this is Geology." ("M.L." I. page 14.) The last, and certainly not the least important of all his duties, consisted in numbering, cataloguing, and packing his specimens for despatch to Henslow, who had undertaken the care of them. In his letters he often expresses the greatest solicitude lest the value of these specimens should be impaired by the removal of the numbers corresponding to his manuscript lists. Science owes much to Henslow's patient care of the collections sent to him by Darwin. The latter wrote in Henslow's biography, "During the five years' voyage, he regularly corresponded with me and guided my efforts; he received, opened, and took care of all the specimens sent home in many large boxes." ("Life of Henslow", by L. Jenyns (Blomefield), London, 1862, page 53.)

Darwin's geological specimens are now very appropriately lodged for the most part in the Sedgwick Museum, Cambridge, his original Catalogue with subsequent annotations being preserved with them. From an examination of these catalogues and specimens we are able to form a fair notion of the work done by Darwin in his little cabin in the "Beagle", in the intervals between his land journeys.

Besides writing up his notes, it is evident that he was able to accomplish a considerable amount of study of his specimens, before they were packed up for despatch to Henslow. Besides hand-magnifiers and a microscope, Darwin had an equipment for blowpipe-analysis, a contact-goniometer and magnet; and these were in constant use by him. His small library of reference (now included in the Collection of books placed by Mr F. Darwin in the Botany School at Cambridge ("Catalogue of the Library of Charles Darwin now in the Botany School, Cambridge". Compiled by H.W. Rutherford; with an introduction by Francis Darwin. Cambridge, 1908.)) appears to have been admirably selected, and in all probability contained (in addition to a good many works relating to South America) a fair number of excellent books of reference. Among those relating to mineralogy, he possessed the manuals of Phillips, Alexander Brongniart, Beudant, von Kobell and Jameson: all the "Cristallographie" of Brochant de Villers and, for blowpipe work, Dr Children's translation of the book of Berzelius on the subject. In addition to these, he had Henry's "Experimental Chemistry" and Ure's "Dictionary" (of Chemistry). A work, he evidently often employed, was P. Syme's book on "Werner's Nomenclature of Colours"; while, for Petrology, he used Macculloch's "Geological Classification of Rocks". How diligently and well he employed his instruments and books is shown by the valuable observations recorded in the annotated Catalogues drawn up on board ship.

These catalogues have on the right-hand pages numbers and descriptions of the specimens, and on the opposite pages notes on the specimens—the result of experiments made at the time and written in a very small hand. Of the subsequently made pencil notes, I shall have to speak later. (I am greatly indebted to my friend Mr A. Harker, F.R.S., for his assistance in examining these specimens and catalogues. He has also arranged the specimens in the Sedgwick Museum, so as to make reference to them easy. The specimens from Ascension and a few others are however in the Museum at Jermyn Street.)

It is a question of great interest to determine the period and the occasion of Darwin's first awakening to the great problem of the transmutation of species. He tells us himself that his grandfather's "Zoonomia" had been read by him "but without producing any effect," and that his friend Grant's rhapsodies on Lamarck and his views on evolution only gave rise to "astonishment." ("L.L." I. page 38.)

Huxley, who had probably never seen the privately printed volume of letters to Henslow, expressed the opinion that Darwin could not have perceived the important bearing of his discovery of bones in the Pampean Formation, until they had been studied in England, and their analogies pronounced upon by competent comparative anatomists. And this seemed to be confirmed by Darwin's own entry in his pocket-book for 1837, "In July opened first notebook on Transmutation of Species. Had been greatly struck from about the month of previous March on character of South American fossils... " ("L.L." I. page 276.)

The second volume of Lyell's "Principles of Geology" was published in January, 1832, and Darwin's copy (like that of the other two volumes, in a sadly dilapidated condition from constant use) has in it the inscription, "Charles Darwin, Monte Video. Nov. 1832." As everyone knows, Darwin in dedicating the second edition of his Journal of the Voyage to Lyell declared, "the chief part of whatever scientific merit this journal and the other works of the author may possess, has been derived from studying the well-known and admirable 'Principles of Geology'".

In the first chapter of this second volume of the "Principles", Lyell insists on the importance of the species question to the geologist, but goes on to point out the difficulty of accepting the only serious attempt at a transmutation theory which had up to that time appeared—that of Lamarck. In subsequent chapters he discusses the questions of the modification and variability of species, of hybridity, and of the geographical distribution of plants and animals. He then gives vivid pictures of the struggle for existence, ever going on between various species, and of the causes which lead to their extinction—not by overwhelming catastrophes, but by the silent and almost unobserved action of natural causes. This leads him to consider theories with regard to the introduction of new species, and, rejecting the fanciful notions of "centres or foci of creation," he argues strongly in favour of the view, as most reconcileable with observed facts, that "each species may have had its origin in a single pair, or individual, where an individual was sufficient, and species may have been created in succession at such times and in such places as to enable them to multiply and endure for an appointed period, and occupy an appointed space on the globe." ("Principles of Geology", Vol. II. (1st edition 1832), page 124. We now know, as has been so well pointed out by Huxley, that Lyell, as early as 1827, was prepared to accept the doctrine of the transmutation of species. In that year he wrote to Mantell, "What changes species may really undergo! How impossible will it be to distinguish and lay down a line, beyond which some of the so-called extinct species may have never passed into recent ones" (Lyell's "Life and Letters" Vol. I. page 168). To Sir John Herschel in 1836, he wrote, "In regard to the origination of new species, I am very glad to find that you think it probable that it may be carried on through the intervention of intermediate causes. I left this rather to be inferred, not thinking it worth while to offend a certain class of persons by embodying in words what would only be a speculation" (Ibid. page 467). He expressed the same views to Whewell in 1837 (Ibid. Vol. II. page 5.), and to Sedgwick (Ibid. Vol. II. page 36) to whom he says, of "the theory, that the creation of new species is going on at the present day"—"I really entertain it," but "I have studiously avoided laying the doctrine down dogmatically as capable of proof" (see Huxley in "L.L." II. pages 190-195.))

After pointing out how impossible it would be for a naturalist to prove that a newly DISCOVERED species was really newly CREATED (Mr F. Darwin has pointed out that his father (like Lyell) often used the term "Creation" in speaking of the origin of new species ("L.L." II. chapter 1.)), Lyell argued that no satisfactory evidence OF THE WAY in which these new forms were created, had as yet been discovered, but that he entertained the hope of a possible solution of the problem being found in the study of the geological record.

It is not difficult, in reading these chapters of Lyell's great work, to realise what an effect they would have on the mind of Darwin, as new facts were collected and fresh observations concerning extinct and recent forms were made in his travels. We are not surprised to find him writing home, "I am become a zealous disciple of Mr Lyell's views, as known in his admirable book. Geologising in South America, I am tempted to carry parts to a greater extent even than he does." ("L.L." I. page 263.)

Lyell's anticipation that the study of the geological record might afford a clue to the discovery of how new species originate was remarkably fulfilled, within a few months, by Darwin's discovery of fossil bones in the red Pampean mud.

It is very true that, as Huxley remarked, Darwin's knowledge of comparative anatomy must have been, at that time, slight; but that he recognised the remarkable resemblances between the extinct and existing mammals of South America is proved beyond all question by a passage in his letter to Henslow, written November 24th, 1832: "I have been very lucky with fossil bones; I have fragments of at least six distinct animals... I found a large surface of osseous polygonal plates... Immediately I saw them I thought they must belong to an enormous armadillo, living species of which genus are so abundant here," and he goes on to say that he has "the lower jaw of some large animal which, from the molar teeth, I should think belonged to the Edentata." ("M.L." I. pages 11, 12. See "Extracts of Letters addressed to Prof. Henslow by C. Darwin" (1835), page 7.)

Having found this important clue, Darwin followed it up with characteristic perseverance. In his quest for more fossil bones he was indefatigable. Mr Francis Darwin tells us, "I have often heard him speak of the despair with which he had to break off the projecting extremity of a huge, partly excavated bone, when the boat waiting for him would wait no longer." ("L.L." I. page 276 (footnote).) Writing to Haeckel in 1864, Darwin says: "I shall never forget my astonishment when I dug out a gigantic piece of armour, like that of the living armadillo." (Haeckel, "History of Creation", Vol. I. page 134, London, 1876.)

In a letter to Henslow in 1834 Darwin says: "I have just got scent of some fossil bones... what they may be I do not know, but if gold or galloping will get them they shall be mine." ("M.L." I. page 15.)

Darwin also showed his sense of the importance of the discovery of these bones by his solicitude about their safe arrival and custody. From the Falkland Isles (March, 1834), he writes to Henslow: "I have been alarmed by your expression 'cleaning all the bones' as I am afraid the printed numbers will be lost: the reason I am so anxious they should not be, is, that a part were found in a gravel with recent shells, but others in a very different bed. Now with these latter there were bones of an Agouti, a genus of animals, I believe, peculiar to America, and it would be curious to prove that some one of the genus co-existed with the Megatherium: such and many other points depend on the numbers being carefully preserved." ("Extracts from Letters etc.", pages 13-14.) In the abstract of the notes read to the Geological Society in 1835, we read: "In the gravel of Patagonia he (Darwin) also found many bones of the Megatherium and of five or six other species of quadrupeds, among which he has detected the bones of a species of Agouti. He also met with several examples of the polygonal plates, etc." ("Proc. Geol. Soc." Vol. II. pages 211-212.)

Darwin's own recollections entirely bear out the conclusion that he fully recognised, WHILE IN SOUTH AMERICA, the wonderful significance of the resemblances between the extinct and recent mammalian faunas. He wrote in his "Autobiography": "During the voyage of the 'Beagle' I had been deeply impressed by discovering in the Pampean formation great fossil animals covered with armour like that on the existing armadillos." ("L.L." I. page 82.)

The impression made on Darwin's mind by the discovery of these fossil bones, was doubtless deepened as, in his progress southward from Brazil to Patagonia, he found similar species of Edentate animals everywhere replacing one another among the living forms, while, whenever fossils occurred, they also were seen to belong to the same remarkable group of animals. (While Darwin was making these observations in South America, a similar generalisation to that at which he arrived was being reached, quite independently and almost simultaneously, with respect to the fossil and recent mammals of Australia. In the year 1831, Clift gave to Jameson a list of bones occurring in the caves and breccias of Australia, and in publishing this list the latter referred to the fact that the forms belonged to marsupials, similar to those of the existing Australian fauna. But he also stated that, as a skull had been identified (doubtless erroneously) as having belonged to a hippopotamus, other mammals than marsupials must have spread over the island in late Tertiary times. It is not necessary to point out that this paper was quite unknown to Darwin while in South America. Lyell first noticed it in the third edition of his "Principles", which was published in May, 1834 (see "Edinb. New Phil. Journ." Vol. X. (1831), pages 394-6, and Lyell's "Principles" (3rd edition), Vol. III. page 421). Darwin referred to this discovery in 1839 (see his "Journal", page 210.))

That the passage in Darwin's pocket-book for 1837 can only refer to an AWAKENING of Darwin's interest in the subject—probably resulting from a sight of the bones when they were being unpacked—I think there cannot be the smallest doubt; AND WE MAY THEREFORE CONFIDENTLY FIX UPON NOVEMBER, 1832, AS THE DATE AT WHICH DARWIN COMMENCED THAT LONG SERIES OF OBSERVATIONS AND REASONINGS WHICH EVENTUALLY CULMINATED IN THE PREPARATION OF THE "ORIGIN OF SPECIES". Equally certain is it, that it was his geological work that led Darwin into those paths of research which in the end conducted him to his great discoveries. I quite agree with the view expressed by Mr F. Darwin and Professor Seward, that Darwin, like Lyell, "thought it 'almost useless' to try to prove the truth of evolution until the cause of change was discovered" ("M.L." I. page 38.), and that possibly he may at times have vacillated in his opinions, but I believe there is evidence that, from the date mentioned, the "species question" was always more or less present in Darwin's mind. (Although we admit with Huxley that Darwin's training in comparative anatomy was very small, yet it may be remembered that he was a medical student for two years, and, if he hated the lectures, he enjoyed the society of naturalists. He had with him in the little "Beagle" library a fair number of zoological books, including works on Osteology by Cuvier, Desmarest and Lesson, as well as two French Encyclopaedias of Natural History. As a sportsman, he would obtain specimens of recent mammals in South America, and would thus have opportunities of studying their teeth and general anatomy. Keen observer, as he undoubtedly was, we need not then be surprised that he was able to make out the resemblances between the recent and fossil forms.)

It is clear that, as time went on, Darwin became more and more absorbed in his geological work. One very significant fact was that the once ardent sportsman, when he found that shooting the necessary game and zoological specimens interfered with his work with the hammer, gave up his gun to his servant. ("L.L." I. page 63.) There is clear evidence that Darwin gradually became aware how futile were his attempts to add to zoological knowledge by dissection and drawing, while he felt ever increasing satisfaction with his geological work.

The voyage fortunately extended to a much longer period (five years) than the two originally intended, but after being absent nearly three years, Darwin wrote to his sister in November, 1834, "Hurrah! hurrah! it is fixed that the 'Beagle' shall not go one mile south of Cape Tres Montes (about 200 miles south of Chiloe), and from that point to Valparaiso will be finished in about five months. We shall examine the Chonos Archipelago, entirely unknown, and the curious inland sea behind Chiloe. For me it is glorious. Cape Tres Montes is the most southern point where there is much geological interest, as there the modern beds end. The Captain then talks of crossing the Pacific; but I think we shall persuade him to finish the coast of Peru, where the climate is delightful, the country hideously sterile, but abounding with the highest interest to the geologist... I have long been grieved and most sorry at the interminable length of the voyage (though I never would have quitted it)... I could not make up my mind to return. I could not give up all the geological castles in the air I had been building up for the last two years." ("L.L." I. pages 257-58.)

In April, 1835, he wrote to another sister: "I returned a week ago from my excursion across the Andes to Mendoza. Since leaving England I have never made so successful a journey... how deeply I have enjoyed it; it was something more than enjoyment; I cannot express the delight which I felt at such a famous winding-up of all my geology in South America. I literally could hardly sleep at nights for thinking over my day's work. The scenery was so new, and so majestic; everything at an elevation of 12,000 feet bears so different an aspect from that in the lower country... To a geologist, also, there are such manifest proofs of excessive violence; the strata of the highest pinnacles are tossed about like the crust of a broken pie." ("L.L." I. pages 259-60.)

Darwin anticipated with intense pleasure his visit to the Galapagos Islands. On July 12th, 1835, he wrote to Henslow: "In a few days' time the "Beagle" will sail for the Galapagos Islands. I look forward with joy and interest to this, both as being somewhat nearer to England and for the sake of having a good look at an active volcano. Although we have seen lava in abundance, I have never yet beheld the crater." ("M.L." I. page 26.) He could little anticipate, as he wrote these lines, the important aid in the solution of the "species question" that would ever after make his visit to the Galapagos Islands so memorable. In 1832, as we have seen, the great discovery of the relations of living to extinct mammals in the same area had dawned upon his mind; in 1835 he was to find a second key for opening up the great mystery, by recognising the variations of similar types in adjoining islands among the Galapagos.

The final chapter in the second volume of the "Principles" had aroused in Darwin's mind a desire to study coral-reefs, which was gratified during his voyage across the Pacific and Indian Oceans. His theory on the subject was suggested about the end of 1834 or the beginning of 1835, as he himself tells us, before he had seen a coral-reef, and resulted from his work during two years in which he had "been incessantly attending to the effects on the shores of South America of the intermittent elevation of the land, together with denudation and the deposition of sediment." ("L.L." I. page 70.)

On arriving at the Cape of Good Hope in July, 1836, Darwin was greatly gratified by hearing that Sedgwick had spoken to his father in high terms of praise concerning the work done by him in South America. Referring to the news from home, when he reached Bahia once more, on the return voyage (August, 1836), he says: "The desert, volcanic rocks, and wild sea of Ascension... suddenly wore a pleasing aspect, and I set to work with a good-will at my old work of Geology." ("L.L." I. page 265.) Writing fifty years later, he says: "I clambered over the mountains of Ascension with a bounding step and made the volcanic rocks resound under my geological hammer!" ("L.L." I. page 66.)

That his determination was now fixed to devote his own labours to the task of working out the geological results of the voyage, and that he was prepared to leave to more practised hands the study of his biological collections, is clear from the letters he sent home at this time. From St Helena he wrote to Henslow asking that he would propose him as a Fellow of the Geological Society; and his Certificate, in Henslow's handwriting, is dated September 8th, 1836, being signed from personal knowledge by Henslow and Sedgwick. He was proposed on November 2nd and elected November 30th, being formally admitted to the Society by Lyell, who was then President, on January 4th, 1837, on which date he also read his first paper. Darwin did not become a Fellow of the Linnean Society till eighteen years later (in 1854).

An estimate of the value and importance of Darwin's geological discoveries during the voyage of the "Beagle" can best be made when considering the various memoirs and books in which the author described them. He was too cautious to allow himself to write his first impressions in his Journal, and wisely waited till he could study his specimens under better conditions and with help from others on his return. The extracts published from his correspondence with Henslow and others, while he was still abroad, showed, nevertheless, how great was the mass of observation, how suggestive and pregnant with results were the reasonings of the young geologist.

Two sets of these extracts from Darwin's letters to Henslow were printed while he was still abroad. The first of these was the series of "Geological Notes made during a survey of the East and West Coasts of South America, in the years 1832, 1833, 1834 and 1835, with an account of a transverse section of the Cordilleras of the Andes between Valparaiso and Mendoza". Professor Sedgwick, who read these notes to the Geological Society on November 18th, 1835, stated that "they were extracted from a series of letters (addressed to Professor Henslow), containing a great mass of information connected with almost every branch of natural history," and that he (Sedgwick) had made a selection of the remarks which he thought would be more especially interesting to the Geological Society. An abstract of three pages was published in the "Proceedings of the Geological Society" (Vol. II. pages 210-12.), but so unknown was the author at this time that he was described as F. Darwin, Esq., of St John's College, Cambridge! Almost simultaneously (on November 16th, 1835) a second set of extracts from these letters—this time of a general character—were read to the Philosophical Society at Cambridge, and these excited so much interest that they were privately printed in pamphlet form for circulation among the members.

Many expeditions and "scientific missions" have been despatched to various parts of the world since the return of the "Beagle" in 1836, but it is doubtful whether any, even the most richly endowed of them, has brought back such stores of new information and fresh discoveries as did that little "ten-gun brig"—certainly no cabin or laboratory was the birth-place of ideas of such fruitful character as was that narrow end of a chart-room, where the solitary naturalist could climb into his hammock and indulge in meditation.

The third and most active portion of Darwin's career as a geologist was the period which followed his return to England at the end of 1836. His immediate admission to the Geological Society, at the beginning of 1837, coincided with an important crisis in the history of geological science.

The band of enthusiasts who nearly thirty years before had inaugurated the Geological Society—weary of the fruitless conflicts between "Neptunists" and "Plutonists"—had determined to eschew theory and confine their labours to the collection of facts, their publications to the careful record of observations. Greenough, the actual founder of the Society, was an ardent Wernerian, and nearly all his fellow-workers had come, more or less directly, under the Wernerian teaching. Macculloch alone gave valuable support to the Huttonian doctrines, so far as they related to the influence of igneous activity—but the most important portion of the now celebrated "Theory of the Earth"—that dealing with the competency of existing agencies to account for changes in past geological times—was ignored by all alike. Macculloch's influence on the development of geology, which might have had far-reaching effects, was to a great extent neutralised by his peculiarities of mind and temper; and, after a stormy and troublous career, he retired from the society in 1832. In all the writings of the great pioneers in English geology, Hutton and his splendid generalisation are scarcely ever referred to. The great doctrines of Uniformitarianism, which he had foreshadowed, were completely ignored, and only his extravagances of "anti-Wernerianism" seem to have been remembered.

When between 1830 and 1832, Lyell, taking up the almost forgotten ideas of Hutton, von Hoff and Prevost, published that bold challenge to the Catastrophists—the "Principles of Geology"—he was met with the strongest opposition, not only from the outside world, which was amused by his "absurdities" and shocked by his "impiety"—but not less from his fellow-workers and friends in the Geological Society. For Lyell's numerous original observations, and his diligent collection of facts his contemporaries had nothing but admiration, and they cheerfully admitted him to the highest offices in the society, but they met his reasonings on geological theory with vehement opposition and his conclusions with coldness and contempt.

There is, indeed, a very striking parallelism between the reception of the "Principles of Geology" by Lyell's contemporaries and the manner in which the "Origin of Species" was met a quarter of a century later, as is so vividly described by Huxley. ("L.L." II. pages 179-204.) Among Lyell's fellow-geologists, two only—G. Poulett Scrope and John Herschel (Both Lyell and Darwin fully realised the value of the support of these two friends. Scrope in his appreciative reviews of the "Principles" justly pointed out what was the weakest point, the inadequate recognition of sub-aerial as compared with marine denudation. Darwin also admitted that Scrope had to a great extent forestalled him in his theory of Foliation. Herschel from the first insisted that the leading idea of the "Principles" must be applied to organic as well as to inorganic nature and must explain the appearance of new species (see Lyell's "Life and Letters", Vol. I. page 467). Darwin tells us that Herschel's "Introduction to the Study of Natural Philosophy" with Humboldt's "Personal Narrative" "stirred up in me a burning zeal" in his undergraduate days. I once heard Lyell exclaim with fervour "If ever there was a heaven-born genius it was John Herschel!")—declared themselves from the first his strong supporters. Scrope in two luminous articles in the "Quarterly Review" did for Lyell what Huxley accomplished for Darwin in his famous review in the "Times"; but Scrope unfortunately was at that time immersed in the stormy sea of politics, and devoted his great powers of exposition to the preparation of fugitive pamphlets. Herschel, like Scrope, was unable to support Lyell at the Geological Society, owing to his absence on the important astronomical mission to the Cape.

It thus came about that, in the frequent conflicts of opinion within the walls of the Geological Society, Lyell had to bear the brunt of battle for Uniformitarianism quite alone, and it is to be feared that he found himself sadly overmatched when opposed by the eloquence of Sedgwick, the sarcasm of Buckland, and the dead weight of incredulity on the part of Greenough, Conybeare, Murchison and other members of the band of pioneer workers. As time went on there is evidence that the opposition of De la Beche and Whewell somewhat relaxed; the brilliant "Paddy" Fitton (as his friends called him) was sometimes found in alliance with Lyell, but was characteristically apt to turn his weapon, as occasion served, on friend or foe alike; the amiable John Phillips "sat upon the fence." Only when a new generation arose—including Jukes, Ramsay, Forbes and Hooker—did Lyell find his teachings received with anything like favour.

We can well understand, then, how Lyell would welcome such a recruit as young Darwin—a man who had declared himself more Lyellian than Lyell, and who brought to his support facts and observations gleaned from so wide a field.

The first meeting of Lyell and Darwin was characteristic of the two men. Darwin at once explained to Lyell that, with respect to the origin of coral-reefs, he had arrived at views directly opposed to those published by "his master." To give up his own theory, cost Lyell, as he told Herschel, a "pang at first," but he was at once convinced of the immeasurable superiority of Darwin's theory. I have heard members of Lyell's family tell of the state of wild excitement and sustained enthusiasm, which lasted for days with Lyell after this interview, and his letters to Herschel, Whewell and others show his pleasure at the new light thrown upon the subject and his impatience to have the matter laid before the Geological Society.