sisting of but two cavities or chambers: the whale, he finds, has warm blood, and a heart constructed on the same type as that of the biologist himself, and consisting of four chambers. The fish is covered with scales: the whale's body-covering consists typically of hairs; and whilst the fish out of water dies, as a rule, because its gills are then removed from the medium from which they derive the oxygen for breathing, the whale breathes by lungs, and, as every one knows, requires to ascend periodically to the surface of the water to inhale the air directly from the atmosphere, like ourselves. The whole internal economy of the fish, albeit that it exhibits the same general type as that of the whale, is of much less complex kind. And, not to penetrate more deeply into the distinctions which separate the whale race from the fish tribe, we may lay stress on one last fact of primary importance in distinguishing the two animals— namely, that whilst the fish was developed from an egg which was hatched externally to the parent body, the whale was born alive and was nourished in its early life by the milk-secretion of its parent. Now, all of these characteristics infallibly demonstrate to the merest tyro in zoology that, so far from a whale being in any sense a fish, it is a true "quadruped" or mammal like ourselves. It finds refuge in the same class which includes the kangaroos and their neighbours as its lowest members or democracy, and apes and man as its aristocrats. The whale, in short, is a mammal with but two well-developed limbs, and occasionally rudiments of two other members; the two front and developed limbs being converted into swimming-paddles or "flippers." It is a quadruped modified for an aquatic life, and resembles the fish only in the fact that its body is built up on one and the same general type, and in its outward modification as a tenant of the " vasty deep." Thus clearly do we observe that the true position of an animal or plant in the living series can only be determined by a reference to the facts of structure. Classification, in other words, is the natural termination to the work begun by the anatomist and the student of development.

Turning to the second question asked by biological science regarding every living being "How does it live?" we find the science of Physiology credited with furnishing the reply to this latter query. Physiology is the "science of functions," a term translatable into meaning that branch of inquiry which shows us how the living mechanism works, and how life is supported in virtue of defined actions which it is the duty of that mechanism to perform. The watchmaker or other artificer who, setting the mechanism he has constructed in motion, professed to instruct us in the manner of its working, would be showing us the "physiology" of the machinejust as previously, when describing its structure, he taught us its "morphology." We may go further still, and add, that, without a

preliminary knowledge of structure, the intelligent appreciation of function, or working, is impossible of attainment. The exact manner in which a watch performs its duties can only be comprehended after an examination of its anatomy or the disposition of its parts. Hence, in living beings," how life is carried on" is a question only to be answered from the knowledge and by the aid of the considerations which the examination of their structure affords and supplies.

Summing up the history of the living being in action which physiology writes for us, we may say that three great functions are performed by every animal and by every plant. The living being has first to nourish itself; to provide for the continual wear and tear to which, in the mere act of living and being, its frame is subjected. The first function of Nutrition thus provides for the support of the individual animal or plant. But death is continually thinning the ́ranks of animal and plant species. As local death, or the decay of the particles of the individual body, is a constant concomitant of individual life, no less true is it that general death is an invariable accompaniment of the life of the race or species. As nutrition-the act of taking and assimilating food-repairs individual loss, so the function of Reproduction repairs the loss and fills the gaps which death has made in the ranks of the race. New beings, through the exercise of this latter function, are brought into the world to take the place on the stage of life of the actors whose parts in the biological drama have already been played out.

Lastly, in the exercise of its living powers, the animal or plant is found to possess certain means for acquiring relations of more or less definite kind with its surroundings. An amoeba-in its way a mere speck of protoplasm-is seen under the microscope to contract its jelly-like body when a food-particle touches its substance; and, as the result of the contact, the protoplasmic speck engulfs the atom in question and duly assimilates it. But for this property of sensitiveness, the life of the animalcule would be equivalent to the existence of the mineral; its power of nourishing its frame and of receiving food really depends on its sensitiveness to the outward impressions produced by the chance contact with its body of the external particles on which it feeds. Withdraw from the protoplasm this sensitiveness, and your animalcule would starve. Sensation and a power of acting, like human units of official nature, upon "information received" through sensation, is a universal attribute of life. Even the fixed plant may, as in the Venus's fly-trap (Dionæa), develop a more sensitive and elaborate apparatus for the capture of prey than many animals of tolerably high grade; and in all plants. there exists living protoplasm which, as its first characteristic, exhibits. sensitiveness and a power of contraction. A snail, irritated by touching the tip of its tentacles, withdraws into the obscurity of

private life for a while, and indicates that it possesses not merely a nervous apparatus analogous to our own, but that such apparatus is used in an exactly similar fashion. A broad likeness exists between a snail's retirement into its shell when touched, and the human act of withdrawing the head from a threatened blow. And so we find that from the animalcule to man, from the lowest plant to the highest member of the vegetable kingdom, there exist means whereby the living being, through the property of sensitiveness or "irritability" (as we may term the general function of nervous tissue or its representative), is brought into relation with its surroundings. This act of relating itself to the outer world in which it lives, constitutes the third function of life wherever found. The nerve-acts whereby man is enabled to think, feel, and move; the actions whereby a daisy closes its florets when the chill of evening falls upon the world; the act of a Venus's fly-trap or a sundew in capturing the insects on which, like vegetable spiders, these plants feed; and the humbler manifestations of sensation seen in the sluggish movement of an animalcule or in the cells of a seaweed-are bound together in one harmonious function, which we name that of Relation, Innervation, or Irritability. To nourish itself, to reproduce its kind, and to maintain relations with the world in which it lives-such is the whole physiological duty of man and animalcule alike; and in the survey of these three functions is comprehended the answer to our second question, "How does the animal or plant live?"

The third inquiry of the biologist, as we have seen, relates to the place and position of the living being on the surface of the worldwhether it be found on the earth itself or in the waters under the earth, whence by deep-sea research the knowledge of its habitat has been drawn. Every animal and every plant, besides a name and designation, possesses a "local habitation" on the earth's surface. The study of structure and the knowledge afforded by physiology take no account of the dwelling-places of animals and plants. "Where is it found?" is thus a question which must also be asked of the biologist; and for the answer we depend upon a third branch of biology, to which the name of Distribution has been given.

The purport of the inquiry, "Where is it found?" requires no explanation. The most natural of queries concerning a living being is that which the child might ask concerning the native habitation of an animal or plant. Outward nature appeals too forcibly to us to render the question, "Where does it come from?" an unnatural one when applied to the animal or plant; the difference between our own land and habitation and those of other men being included in some such interrogation as that involved in the questions which the science of Distribution professes to answer. No more interesting queries can well be imagined within the whole range of natural-history study

than those included within the sphere of this third division of biology. Why, for instance, are kangaroos and animals of like grade only found in Australia and adjacent islands? Why are the opossumsnear relations of the kangaroos-absent from the Australian home of their nearest kith and kin? and why do they occur in America, when natural expectation would have placed them in Australia? Why are antelopes well-nigh confined to Africa, which has no true deer, whilst the deers are otherwise world-wide in their distribution? Why are humming-birds only found in the New World, over the length and breadth of which they are widely distributed? Why are the monkeys of America absolutely different from those of the Old World? and why are those found in Madagascar, in turn, so varied from their neighbours of Asia and Africa? Why are sloths and armadillos only found in South America? Such are a very few of the queries which Distribution asks, and to which this science endeavours to supply an answer.

We thus perceive, clearly enough, that the situation and position of an animal or plant on the surface of the earth is no mere matter of chance, but is as much the result of law, and has been as clearly brought about by the circumstances which regulate existence as a whole, as its structure is the result of laws of development acting in definite fashion and ordered sequence. Distribution, it is true, is a biological science as yet in its infancy. It presents us, we may note, with two aspects, under one of which we settle the place and position of an animal in space, that is, in the world as it now exists-such is Geographical Distribution. Through the other aspect of this science, we determine, by the aid of the history of fossils, whether it had an existence in the past history of our earth, and if so, under what conditions it lived. This latter phase of the subject is named Geological Distribution, or distribution in time. The importance of distribution as a branch of biology grows and increases daily, as we perceive that the answers to many puzzles and problems of life are bound up in the replies we are able to furnish to the question, "Where is the animal (or plant) found ?"

has

At this stage of biological investigation many naturalists might be tempted to call a halt. Having ascertained, as fully as may be, the structure, physiology, and distribution of an animal or plant, the investigation of the living form might be regarded as complete. Contrariwise, however, the tendency of the biology of past years been to lay increasing stress on a fourth inquiry concerning every living thing-namely, "How has it come to be what it is?" Such a question is tantamount to the inquiry, "How and why was the living being created so?"—an interrogation which, even a few years back, would have sounded as an attempt to probe the mystery of divine intent, and which, as such, would have been relegated to the domain

of the unscientific, if not to that of the impious as well. But considerations of theoretical impiety have no effect in face of the need for knowledge. If the speculation how any planet was framed, and if the formation of a nebular hypothesis, or the promulgation of a theory of elliptical orbits, was a warrantable procedure-nay, even necessity of astronomical knowledge, one may well be excused for failing to discover the unwarrantableness of speculation concerning the origin of animals and plants. Especially, too, if the way of creation, as biological science believes, has not been through successive acts of supernatural interference with the matter of life and the manner of living, but through the modification-slow, gradual, natural, and prolonged-of pre-existing species, the justification for the query, "How has this animal or that plant assumed its form and place in the world?” lies on the face of nature itself. If, as is apparent to all biologists at least, the way of creation is traceable in the forms and developments of living beings, we are bound to investigate that history, as a part of the duty laid upon scientific truth-seeking and upon biological investigation.

The impiety so much talked of in past years, but of which one happily hears but little now, if it exists at all, is illustrated solely in the absolute scepticism of those who refuse to admit and believe in the right of man to read and construe, as reason dictates, the records written in the fair face of creation itself. Persons who deem it impious in the scientist to assert that he can trace the evolution of this animal or that plant, present the best possible frame of mind for the development of the very scepticism the existence of which they are the first to deplore. The wilful folding of the hands in deprecation of scientific investigation, and the shutting of the eyes in a so-called "orthodox" and slumbering ignorance of the facts of nature, is the procedure of all others best calculated to sap the foundations of religion itself. It is such ideas which Dr. Martineau, with his accustomed ability, has ably denounced when he says, "What, indeed, have we found by moving out along all radii into the Infinite ?-that the whole is woven together in one sublime tissue of intellectual relations, geometric and physical-the realised original, of which all our science is but the partial copy. That science is the crowning product and supreme expression of human reason. . . Unless, therefore, it takes more mental faculty to construe a universe than to cause it, to read the Book of Nature than to write it, we must more than ever look upon its sublime face as the living appeal of thought to thought." These are words worth reflecting upon; and they certainly admit from the side of liberal theology the full, free, and unrestrained right of science to investigate fully and hopefully whatever facts or aspects of Nature lie to her hand. They present, if need exists for such apology, the fullest justification of the scientific investigator's work,