anatomy could be applied to the classification of animals according to their whole organisation in a far more natural manner than by the easier method of Linnæus. Later on, when improved microscopes and refined optical and chemical tests became available, the study of anatomy was carried beyond the knowledge of the parts and organs of the bodysuch as bones, muscles, blood-vessels, and nerves-to the investigation of the tissues, fibres, and cells of which these are composed; while the physiologists devoted themselves to an inquiry into the mode of action of this complex machinery, so as to discover the use of every part, the nature of its functions in health and disease, and, as far as possible, the nature of the forces which kept them all in action.

Down to the middle of the present century the study of nature advanced with giant strides along these separate lines of research, while the vastness and complexity of the subject led to a constantly increasing specialisation and division of labour among naturalists, the result being that each group of inquirers came to look upon his own department as more or less independent of all the others, each seemed to think that any addition to his body of facts was an end in itself, and that any bearing these facts might have on other branches of the study or on the various speculations as to the "system of nature" or the "true method of classification" that had at various times been put forth was an altogether subordinate and unimportant matter. And, in fact, they could hardly think otherwise. For, while there was much talk of the "unity of nature," a dogma pervaded the whole scientific world which rendered hopeless any attempt to discover this supposed unity amid the endless diversity of organic forms and structures, while so much of it as might be detected would necessarily be speculative and unfruitful. This dogma was that of the original diversity and permanent stability of species, a dogma which the rising generation of naturalists must find it hard to believe was actually held, almost universally, by the great men they look up to as masters in their several departments, and held for the most part with an unreasoning tenacity and scornful arrogance more suited to politicians or theologians than to men of science. Although the doctrine of the special and independent creation of every

species that now exists or ever has existed on the globe was known to involve difficulties and contradictions of the most serious nature, although it was seen that many of the facts revealed by comparative anatomy, by embryology, by geographical distribution, and by geological succession were utterly unmeaning and even misleading, in view of it; yet, down to the period we have named, it may be fairly stated that nine-tenths of the students of nature unhesitatingly accepted it as literally true, while the other tenth, though hesitating as to the actual independent creation, were none the less decided in rejecting utterly and scornfully the views elaborated by Lamarck, by Geoffroy St. Hilaire, and at a much later date by the anonymous author of the Vestiges of Creation that every living thing had been produced by some modification of ordinary generation from parents more or less closely resembling it. Holding such views of the absolute independence of each species, it almost necessarily followed that the only aspect of nature of which we could hope to acquire complete and satisfactory knowledge was that which regarded the species itself. This we could describe in the minutest detail; we could determine its range in space and in time; we could investigate its embryology from the rudimental germ, or even from the primitive cell, up to the perfect animal or plant; we could learn every point in its internal structure, and we might hope, by patient research and experiment, to comprehend the use, function, and mode of action of every tissue and fibre, and ultimately of each cell and organic unit. All this was real knowledge, was solid fact. But, so soon as we attempted to find out the relations of distinct species to each other, we embarked on a sea of speculation. We could, indeed, state how one species differed from another species in every particular of which we had knowledge; but we could draw no sound inferences as to the reason or cause of such differences or resemblances, except by claiming to know the very object and meaning of the creator in producing such diversity. And, in point of fact, the chief inference that was drawn is now proved to be erroneous. It was generally assumed, as almost self-evident, that the ultimate cause of the differences in the forms, structures, and habits of the organic productions of different countries, was

that each species inhabiting a country was specially adapted to the physical conditions that prevailed there, to which it was exactly fitted. Even if this theory had been true, it was an unproductive ultimate fact, for it was never pretended that we could discover any reason for the limitation of humming-birds and cactuses to America, of hippopotami to Africa, or of kangaroos and gum-trees to Australia; and we were obliged to believe either that these countries possessed hidden peculiarities of climate or other conditions, or that this was only one out of many unknown and unknowable causes determining the special action of the creative power. All this was felt to be so unsatisfactory that the majority of naturalists openly declared that their sole business was to accumulate facts, and that any attempt to co-ordinate these facts and see what inferences could be drawn from them was

altogether premature. In this frame of mind, year after year passed away, adding its quota to the vast mass of undigested facts which were accumulating in every branch of the science. The remotest parts of the globe were ransacked to add to the treasures of our museums, and the number of known species became so enormous that students began to confine themselves not merely to single classes, as birds or insects, but to single orders, as beetles or land-shells, or even to smaller groups, as weevils or butterflies. All, too, were so impressed with the belief in the reality and permanence of species, that endless labour was bestowed on the attempt to distinguish them—a task whose hopelessness may be inferred from the fact that, even in the well-known British flora, one authority describes sixty-two species of brambles and roses, another of equal eminence only ten species of the same groups; and it is by no means uncommon for two, five, or even ten species of one author to be classed as a single species by another. All this time geologists had been so assiduously at work in the discovery of organic remains that the extinct species often equalled, and, in some groupsas the Mollusca-very far exceeded, those now living on the earth, and these were all found to belong to the very same classes and orders as the living forms, and to form part of one great system. Much attention was now paid to the geological succession of the different groups of animals, which

were found to exhibit a progressive advancement from ancient to recent times, while the breaks in the series between each great geological formation were held to show that the older forms of life had been destroyed, and were replaced by a new creation of a more advanced organisation suited to the altered conditions of the world.

And thus, perhaps, we might have gone on to this day, ever accumulating fresh masses of fact, while each set of workers became ever more and more occupied in their own departments of study, and, for want of any intelligible theory to connect and harmonise the whole, less and less able to appreciate the labours of their colleagues, had not Charles Darwin made his memorable voyage round the world, and thenceforth devoted himself, as so many had done before him, to a life of patient research in the domain of organic nature. But how different was the object attained! Others have added greatly to our knowledge of details, or created a reputation by some important work; he has given us new conceptions of the world of life, and a theory which is itself. a powerful instrument of research; has shown us how to combine into one consistent whole the facts accumulated by all the separate classes of workers, and has thereby revolutionised the whole study of nature. Let us endeavour to see by what means he arrived at this vast result.

The Voyage of the BEAGLE

Passing by the ancestry and early life of Darwin, which have been made known to the whole reading public by many biographical notices and recently by the publication of his Life and Letters, we may begin with the first event to which we can distinctly trace his future greatness-his appointment as naturalist to the Beagle, on the recommendation of his friend and natural-history teacher, Professor Henslow, of Cambridge University. It was in 1831, when Darwin, then twenty-two years of age, had just taken his B.A. degree, that he left England on his five years' voyage in the Southern Hemisphere. It is probably to this circumstance that the world owes the great revolution in our conception of the organic world so well known as the Darwinian theory. The opportunity of studying nature in new and strange lands;

of comparing the productions of one country with those of another; of investigating the physical and biological relations of islands and continents; of watching the struggle for existence in regions where civilisation has not disturbed the free action and reaction of the various groups of animals and plants on each other; and, what is perhaps more important still, the ample leisure to ponder again and again on every phase of the phenomena which presented themselves, free from the attractions of society and the disturbing excitement of daily association with contemporary men of science,these are the conditions most favourable to the formation of habits of original thought, and the months and years which at first sight appear intellectually wasted in the companionship of uncivilised man, or in the solitary contemplation of nature, are those in which the seed was sown which was destined to produce in after years the mature fruit of great philosophical conceptions. Let us then first glance over the Journal of Researches, in which are recorded the main facts and observations which struck the young traveller, and see how far we can detect here the germs of those ideas and problems to the working out of which he devoted a long and laborious life.

The Journal of Researches

The question of the causes which have produced the distribution and the dispersal of organisms seems to have been a constant subject of observation and meditation. At an early period of the voyage he collected infusorial dust which fell on the ship when at sea, and he notes the suggestive fact that in similar dust collected on a vessel 300 miles from land he found particles of stone above the thousandth of an inch square, and remarks: "After this fact, one need not be surprised at the diffusion of the far lighter and smaller sporules of cryptogamic plants." He records many cases of insects occurring far out at sea, on one occasion when the nearest land was 370 miles distant. He paid special attention to the insects and plants inhabiting the Keeling or Cocos, and other recently formed coralline or volcanic islands; the contrast of these with the peculiar productions of the Galapagos evidently impressed him profoundly; while the remarkable facts pre