Again, to know living animals thoroughly it is necessary also to be acquainted with extinct animals, so we cannot have an adequate conception of the world of plants without an acquaintance with its fossil forms-forms some of which afford evidence of startling climatic changes, as do the fossil vines and magnolias of the Arctic region.

But it may be asked, if the multitude of living forms is so great, why should the Natural History of plants and animals be treated simultaneously? Has not the progress of science been accompanied by an increasing division of labor, and is it not wise of naturalists to devote their whole lives to some special group? To this it may be replied, that modern science tends both to unite and to separate the several departments of inquiry. The area to be explored is so vast, and contains such rich variety, that no human mind can hope to master the whole study of either animals or plants. On this account some naturalists are no longer content with being exclusively ornithologists or entomologists, or with devoting themselves to single primary groups of birds or insects, but spend their whole time and wisely so-upon some still more subordinate section of zoology. Nevertheless, such students should also give time to wider study, without which they cannot really understand the special groups to which they are devoted. Such subdivision moreover has, as Goethe remarked, a narrowing tendency. Indeed, the necessity for each student to understand various branches of science is constantly increasing.

A certain knowledge of astronomy and chemistry has become necessary to the geologist, and of geology and chemistry to the biologist. Again, the progress of knowledge has more and more revealed the intimate connection which exists between the two great groups of living creatures-animals and plants. So intimate, indeed, is this connection now seen to be that, in spite of the manifest differences between most animals and plants, the position, or even the existence, of the line which is to divide these organisms is a matter of dispute. It has thus become manifestly impossible to understand adequately the creatures belonging to one of these groups without a certain acquaintance with those

a

belonging to the other group. The powers which animals possess cannot be satisfactorily understood without knowledge of the corresponding powers of plants. Our knowledge, for example, of animal nutrition and reproduction would be very incomplete unless we had a conception of these processes generally, and therefore of the modes in which they take place in plants also. On these accounts it is desirable that both the great groups of living creatures should be considered conjointly, and the study of living organisms treated as one great whole.

An objection of an opposite nature may, however, be made to the plan here advocated. It may be objected that plants and animals should not be considered separately from minerals, but that all terrestrial productions should be treated of as one whole, and their substantial composition and powers exhibited as diverging manifestations of one great unity. In support of this objection may be urged that very increasing inter-relation and cross-dependency between the sciences which have been just referred to. It may be contended that, though animals and plants do indeed require to be treated as one whole, yet they do not form a really isolated group for the following reasons. mineral aggregation in crystals are imitated in the growth of certain animals. The ultimate constituents of the organic and inorganic worlds are the same. The physical forces-light, heat, and electricity-are both needed by and are given off from living organisms, as manifestly by fire-flies, warm-blooded animals, and the electric eel. The diverse manifestations of life are thus, it may be said, merely due to the play of physical forces upon very complex material conditions.

The laws of

To this it may be replied that, at least practically, the living world does constitute a domain apart, and the Natural History of animals and plants (or Biology) a very distinct science, for all that it reposes upon and is intimately connected with the sciences of non-living matter. It may also be contended that there really is a fundamental distinction between the activities of even the lowest living creature and all merely physical forces. For even if the several separate actions of organisms can be performed

by inorganic bodies, yet no inorganic body displays that combination of forces which characterises any living being. The very composition, again, of the organic world differs strikingly in its complexity from that of the inorganic.

Assuming then, provisionally, that animals and plants may together be reasonably separated off from the non-living world and treated as one whole, we find that whole to present remarkable characters of both change and permanence. Individual organisms, at longer or shorter intervals, disappear and are replaced by others like them, and such succession has in some cases endured for very prolonged periods. In most cases, however, kinds as well as individuals have arisen, had their day and died, and have been succeeded by kinds more or less divergent; and this process of replacement has occurred again and again. Has the whole series of successions also had its beginning, or has vegetable life eternally flourished on our planet and eternally nourished race after race of diverse animal tribes? The answer to this question (as far as it can be answered by Physical Science) is, of course, to be sought in the Natural History, not of organic beings, but of the earth and other planets of our system. But let it be granted that the duration of terrestrial life is only, when estimated by sidereal epochs, as the up-growth of a day; yet measured by any more familiar standard its antiquity is such as the imagination refuses to picture. More than this: even the various kinds of animals and plants have had, and have, at least a relative constancy and permanence. Na ture, as we see it, does not present a scene of confused and evanescent forms in a state of Protean change. Were such the case our existing classifications could not have been devised. Our minds perceive that the living world possesses certain permanent characters, and it suggests conceptions not only of "order," "causation," "utility," "purpose," but also of "types" and "creative ideas," to attempt to estimate the value of which would be to enter upon philosophy; for the value to be assigned to such conceptions depends upon the system of philosophy which any one may deem the more reasonable. The advocacy of any system of philoso

phy would be quite out of place in this Essay. Here a single observation must suffice. Those who believe that the First Cause of all creatures which live or have lived is a Divine Intelligence having a certain relation of analogy with the intelligence of man, must also believe that all creatures respond to the ideas of such creative Intelligence. They must also further believe that in so far as the ideas we derive from the study of creatures are true ideas-that is, truly correspond with their objects— such ideas must respond, however imperfectly, to the eternal ideas of such a Divine Intelligence, since things which agree with the same thing must in so far agree with one another.

Remote as such questions may appear to be from the study of Natural History, they have during the present century much occupied the attention of distinguished naturalists. They have also been the occasion of investigations which, as we shall shortly see, have borne fruit the value of which all scientific men now admit. These investigations have called forth a new conception as to the whole mass of living creatures, and of their relations one to another-a conception which renders inadequate all previous pictures of the world of organic life.

From our present standpoint, that world, and indeed the entire universe, may be not inaptly symbolized by a waterfall, such as that of Terni, with its look of changelessness due to unceasing changes, themselves the result of a permanence not at first apparent. The well-known rainbows above the great clouds of sun-lit spray look like fixed and almost solid structures. Though the spectator knows that the same falling water cannot be seen for many seconds, and that the persistence of the elements of color must be even less, yet an impression of persistence and stability remains which, though in some respects an illusion, is not altogether false. Though the physical elements are fleeting, yet both the cascade and its iridescent arcs are persistent-ideally in the mind which apprehends them, and really in those natural laws and that definite arrangement of conditions which continually reproduce the ceaseless flux accompanying their persistence.

Similarly the ocean, with its obvious changes of tides and currents, storms and calms, has been a type of changefulness; and yet viewed in comparison with the upheavals and depressions of the earth's solid surface there is a relative, though by no means absolute, truth in the words :

"Time writes no wrinkle on thy azure brow Such as creation's dawn beheld, thou rollest now!"

But science reveals a succession of changes far from obvious which have taken place since the first fluid film condensed from the hot vapor of the earth's primeval atmosphere. Such are, changes in its composition, its temperature and its living inhabitants, from the time when it swarmed with extinct predecessors of our present crabs, cuttle-fishes, and star-fishes; and afterwards, when huge reptiles dominated in it, till they yielded place to the whales and dolphins of a later epoch, and till at last, after untold ages, the canoes of the earliest races of mankind began at last to ripple its waters.

With the advent of man began a succession of ideal changes. For the growth of knowledge causes our ideas of each part of the universe to alter and grow more exact, just as the aspects of objects change as they may be viewed through a succession of less refracting and more transparent media. How different was the ancient conception of the ocean as a fluid boundary encircling the flat plane of the earth, from that obtained by Columbus when, having traversed an unknown ocean and reached a new world, he exclaimed "Il mondo e poco!" To-day deep-sea explorations are giving us new conceptions, and its Natural History needs re-writing from a fresh standpoint.

The whole universe of fixed-stars and nebulæ may also be conceived as a vast fountain of light and motion. For though (save for the occasional temporary brightness of some world in conflagration, and save for the apparent diurnal revolution of the heavens) it is apparently changeless; yet reason exhibits it to us as an area of ceaseless change. Indeed, as races of living beings succeed each other, so we may fancy that the falling together of worlds and systems

may generate new suns and worlds, like the fresh flowers of a new spring.

But if the image of the ocean as reflected in the mind of man has repeatedly changed in the course of ages, this is still more the case as regards the starry vault. A collection of visible divinities; a hieroglyphic to be puzzled over by the soothsayer; a concentric series of starstudded crystal spheres; and finally, the more and more consistent mind-pictures of Copernicus and Galileo, Kepler and Newton! If it is difficult now to realize the change of view introduced by the discovery of Columbus, it is almost impossible to do so with respect to that which was occasioned by the acceptance of heliocentric astronomy, and which of course rendered a new description of the heavens inevitable.

These considerations may serve to prepare us for analogous changes with respect to our present subject-organic nature. This likewise has not only its real elements of permanence and change, but also its ideal changes, due to the different modes in which it has presented itself to men's minds at different stages of discovery. Such changes render necessary fresh descriptions at successive epochs, and one such epoch is that in which we live.

Animals and plants must always, to a greater or less extent, have occupied the attention of mankind. It is probable that a certain amount of pleasure was felt even in primeval times in observing living beings. The child of to-day delights in the companionship and observation of animals, and in the childhood of the human race animals were regarded as objects of interest and curiosity as well as of utility in furnishing food and clothing. That such was the case seems evident from the portraits which have come down to us of the reindeer and the mammoth (the extinct woolly elephant), traced on bones by the flint-workers, their contemporaries.

Indeed, the earliest of our race could not avoid a certain study of animals the capture of which they needed for their food or clothing. But in addition to attention due to such needs, many phenomena of animal life are well fitted to strike a savage mind, and this the more from that sharpness of the senses which the ruder races of men possess.

The

earliest hunters must have observed the habits of their prey, and have incidentally noticed in their pursuit peculiarities of other creatures, which were not those they pursued, but were related to them as enemies or dependents.

In temperate regions certain phenomena of animal and plant life must very early have forced upon man's attention their regular recurrence, coincidently with that of the seasons. For with the annual reappearance of certain constellations men must have noticed such orderly recurrence of flowers and fruits, and the return of migrating birds. The obtrusive note of the cuckoo, and the quick gliding flight of the swallow, must have early been welcomed as the harbingers of approaching summer.

In this way a series of recurring changes a cycle of phenomena-must have come to be observed. In other words, both permanence and change must have been noted as existing simultaneously in the organic world.

Such conceptions must, of course, have been of the most incomplete and rudimentary character, since the mind can only bring back from the observation of the external world that which it has gained the power of apprehending. The traveller who is ignorant of history and natural science comes back from imperial Rome or sacred Athens, from the impressive solitude of Carnac or the busy quays of Trieste, but little the richer intellectually for the many instructive objects which have met his unappreciating gaze. Thus, with the cultivation or debasement of men's minds, the mental images and intellectual conceptions they form of Nature necessarily undergo corresponding changes, and the surrounding conditions of scene and climate must also largely influence their interest in, and their conceptions of, natural objects. The ancient Egyptians, enclosed in their narrow limestone valley, bounded by desert sands and the hot and riverless Red Sea, do not seem to have been favorably circumstanced for the development of a great love of Nature. Yet their frescoes show that apes, antelopes, leopards, giraffes, and other strange beasts were objects of careful attention; and Solomon's taste for natural knowledge may have found its parallel amongst

Egyptian priests long anterior to the scientific glory of Alexandria.

The Greeks, more happily situate in their beautiful land, botanically so wealthy, and which is split up into so many islands, and has a coast line so irregular through many estuaries, can hardly have failed to appreciate organic nature, seeing that they loved not only human beauty, but that of earth, sea, and sky also. But, however that may be, it is certain that it was there that Natural History first attained a considerable development under an august master. It was congruous that the people who so early attained a social culmination in art, the drama, history, rhetoric, and poetry, constituting them the models and teachers of mankind for thousands of years to come, should have also led the way in Biological Science.

Aristotle, the first-known true man of science, must be considered (from his knowledge of recondite points of anatomy, and from his sketch of animal classification) to have been one who bore within him in germ the biology of later ages. Such a man could not have arisen among a people to whom the investigation of Nature was new or unwelcome.

The legal Roman spirit seems to have had little inclination for the study of Nature, yet in Pliny we meet with the proto-martyr of science. The great song of Lucretius is full of sympathy with organic life in all its forms; and poetry like that of the Georgics must have been intended for minds alive to rustic beauty and the harmonies of rural life.

Whether such incipient scientific culture as existed in classical times would or would not, if left to itself, have soon ripened into that of the modern world, cannot be proved. The fall of the Roman Empire, however, made retrogression inevitable. It may be that such retrogression has had its scientific compensation. For, judging of the source by the outcome, the tribes which issued from the glades of the great Hyrcanian forest must have brought with them a deep, innate love of natural beauty. As the floods of tumultuous invasion subsided, and were succeeded by disturbances comparatively local, Teutonic homesteads began to appear on sites

which seem to have been in part chosen from a love for the picturesque. Soon, one by one, also arose the monastic cradles of medieval civilisation, sometimes nestling in leafy dells by streams or lakes, sometimes perched on mountain crags with difficulty accessible.

With the advent of the thirteenth century came the first pale dawn of that renaissance which, rapidly maturing, burst on the world in its full blaze three centuries later.

It was then that the naturalistic spirit began to assume that predominance which it has ever since retained. Discovery on discovery in every department of science opened out fresh vistas on all sides to the gaze of eager students, and the immensity of the task before inquirers became more manifest to them at each step made in advance.

The past also began to acquire a new significance, for the study of it (as made known in terrestrial deposits) suggested the modern view of the mutability of the earth's surface. No doubt in very early times the occasional discovery of fossil shells and bones-disclosed by some land-slip may have led to vague surmises, as the finding of elephants' bones (many of which so much resembled human bones) may have given rise to tales of giants. With the advance from primeval to classical times clearer notions arose, and Pythagoras (according to Ovid) promulgated the most rational view as to the excavating action of rivers, the upheaval and submergence of land and similar phenomena.

But in the Middle Ages these views seem to have faded from view, so that when in the sixteenth century fossil remains began to be collected in Italy and their significance correctly appreciated, an important revolution in men's minds commenced.

In spite, however, of the gradually clearer apprehension of the fact that many living forms had become extinct, the belief in the fixity of the different kinds of animals and plants was accepted as a matter of course.

There were, however, exceptions to this belief as to fixity which continued to be made, as they had been made during the Middle Ages. During those ages creatures, such as worms and flies, had been supposed to be spontaneously generated by

the action of the sun on mud and in other ways, and creatures which were erroneously supposed to be hybrids had also been supposed to have been occasionally generated. With these exceptions, however, all animals were supposed to have existed unchanged and without fresh creations since their first formation after the beginning of the world.

The interest felt in all the natural sciences continued to increase through the seventeenth and eighteenth centuries, and therewith went on a rapid augmentation in the number of known species of animals and plants.

Much gratitude is due from us to the great compilers of those centuries whose ponderous works were treasure-houses of the natural history of their day. Conspicuous above all was Aldrovandus, whose thirteen folios began to appear in 1640, to be followed in the next century by the richly illustrated folios of Seba.

Thus the way was gradually prepared for a decisive step in advance, marking the first great epoch in the modern natural history of living beings. Such a step was the introduction of a good classification.

It is, of course, difficult to acquire, and impossible to retain and propagate, a thorough knowledge of any very numerous set of objects, unless they are systematically grouped according to some definite plan of classification. On this account the study of living creatures (to the vast number of which attention. has been directed) stood in especial need of some convenient arrangement, if only for the purpose of serving as a memoria technica.

Attempts at a classification of living beings had been made by many naturalists from Aristotle downwards, and amongst the more recent, that of John Ray* (1628-1705) may be honorably distinguished. But it was not till 1735 that a classification was put forward which marked that epoch in the study of natural history above adverted to. It was promulgated by the publication of the Systema Natura of Linnæus. His genius also did away with that obstacle

*See his Methodus plantarum nova, 1682, and his Animalium quadrupedum et serpentini generis, 1693.