them in the anatomical theatre. In the first case the knowledge is hearsay, in the second it is the result of close individual observation, and is therefore real.

Now it is the acquisition of a real and substantial basis of facts -facts which must be verified again and again by the observing eye and sensitive touch-to which physical and biological science, as an engine of education, should first prompt the student. In other studies words come to him invested with the authority conferred by the name of some master. In these he is to believe what he sees and can prove by experiment.

If it be asked why two such nearly related subjects as Anatomy and Physiology should be studied so differently, and with such different results, we think the answer is near at hand. Comparative anatomy, as a branch of scientific education, has, until recently, been almost entirely neglected, and even now is not extensively taught. Comparative physiology cannot be studied without a preliminary groundwork of comparative anatomy. While, thirdly, almost all advance in human physiology must depend on experiments made on the lower animals. In these three statements we have indicated what we conceive to be the true answer. Students cannot themselves work out the physiological problems connected with the nerves in question, or any other similar part, because they are not sufficiently familiar with their relative position in the only bodies on which experiment is possible, viz. those of the lower animals. When a course of comparative anatomy, carried out not merely by dry lectures, but by actual dissections and demonstrations on familiar representative animals, be considered an integral part of a medical education, and not till then, will physiology be generally studied according to a better method.

But if an English student of medicine of to-day desires to fit himself for pursuing physiological studies after the manner indicated, or by practical dissection to enlarge his knowledge of those empirical laws which underlie animal forms, whither is he to look for a guide -such a guide as books on anthropotomy afford him in his practical study of the human body? Except the book before us, we do not know any that would serve his purpose. There are many books of great value which give the results of comparative anatomy; as, for example, Professor Owen's great work; or the remarkably lucid and able Introduction to the Classification of Animals,' by Professor Huxley. But their scope and aim are different. Professor Rolleston's book does then, we think, supply a real want.

By the aid of its very clear descriptions, and, if possible, still clearer figures, the student is enabled to dissect and recognize all the salient points in the anatomy of a rat, pigeon, frog, and many another familiar and typical animal. The volume is not intended for the mere reader of comparative anatomy, and will do him no good

or at least no more good than any other able treatise on the subject. It is designed as an aid to the practical worker; not to burden his memory and confirm him in the enervating habit of receiving on trust statements which ought to be verified by observation, but to educate him into the way of educating himself. Though written primarily for the benefit of students of the University of Oxford, in the museum of which institution an illustrative series of preparations exists, we think we have said enough already to prove that its advantages need by no means be limited to them; but that it will prove most useful to all those who desire, like we did in our own student days, a reliable guide by which to work. To go through the book as the author designs it to be gone through, and as the reader for his own sake should make up his mind to go through it, will involve both time and labour; but they will be time and labour well expended.

There are three parts to the work. First, an introduction, "giving a classification of the animal kingdom, with a zootomical account of the various sub-kingdoms and their subordinate divisions and classes." Secondly, a "description of certain readily procurable specimens, which illustrate in the concrete a very large number of the systematic descriptions contained in the introduction;" and thirdly, descriptions of figures supplementary to the descriptions of specimens, and designed to aid those specimens in "furnishing that groundwork of particular facts, without which it is impossible to obtain any real knowledge or permanent hold of general principles." This endeavour to erect the principles of the science on a firm basis of fact, which the student is taught how to observe for himself, is the unique and most valuable feature of the book.

Of the three parts, the first consists of 168 pages, and is recommended in the preface to be studied after the preparations and specimens whose descriptions succeed it. We do not quite see, as these are to be read first (as they undoubtedly should be, and that too as a commentary on actual specimens; all the better if actually made by the reader), why they should be placed second. This is a matter of small moment perhaps, except that a book is generally written in the order in which it is intended to be read; and that a good many people either pass over prefaces altogether, or read them just as authors write them, namely, after they have finished the works to which they are intended to be the real introductions. One of the most striking features of this first part is its extreme truthfulness. No attempt is made to construct a completer system than Nature herself has given. Everything in it is reliable, because in everything Nature has been followed, not led. Nothing is easier than to fix on some one character as a basis, on which a zoological system can be constructed, whose symmetry and philosophic completeness shall captivate the mere reader of zoology-nothing, except the readiness

with which this symmetry can be shown to be unreal. We could point to more than one book, whose numerous editions testify to their numerous readers, written on this principle. In the "Introduction" before us, if we miss a little of the charm of a completeness, easily attained when men construct animal kingdoms out of their own imaginings, we recognize in every page the far more substantial advantage of a severely conscientious truthfulness. Scarcely a fact of broad and general application is stated, that has not the "but," which introduces all the exceptions to it, immediately after; and it will be a great satisfaction to the student of the book to know that, however much he may have to supplement the knowledge it affords him as the science of comparative anatomy may advance, he will have little or nothing to unlearn.

The admirable calmness and temper displayed when the passing discussion of any biological theory is rendered necessary; the carefulness with which conclusions which are merely probable are distinguished from others that bear the stamp of certainty; the evenness with which the balance is held between opposing probabilities-as for example at pp. xxv. and clxii. respectively, where the theories of evolution and of the existence of a regnum protisticum are reviewed; and the readiness everywhere manifested to accept any new truth when proved, coupled with a cautiousness in disparaging the old simply because it is so, cannot fail to exercise a wholesome influence on the mind of the reader.

In two ways we venture to think the value of this part might be enhanced. First, by the addition to it of some such glossary as that appended by Dr. Pye Smith to Professor Huxley's "Introduction." Secondly, by the devotion of a single figure and about a page of description to the elucidation of the constituent parts of a complete vertebra; in the absence of which the student is referred, at p. 9, Part II., to Professor Owen's 'Descriptive Catalogue,' a work not easily obtained, except by those living in Metropolitan or University

towns.

The second part consists of the descriptions of fifty preparations obtained from representative, and for the most part easily procurable animals, such as the rat, pigeon, common fowl, frog, perch, crayfish, &c. While they are so clear as to enable the student easily to recognize in the preparation before him its anatomical details, or to make the preparation for himself if he has not access to a museum containing it, they are something more than mere descriptive sketches of the particular animals under consideration. Each serves as a text for a discourse on the entire class, and side by side with the account of every organ are allusions to homologous organs of creatures in allied orders. With the descriptive anatomy of the common crayfish, for example, are frequent comparisons of its different parts with those of other Decapods, both brachyurous and macrourous; of Iso

pods, Amphiopods, and many others; so that by being thus grouped around one central and familiar figure, the resemblances and differences can be better appreciated and more easily remembered.

In the third part are twelve plates containing drawings of nine dissections of common animals, executed from the dissections themselves, by Mr. G. Crozier, formerly draughtsman to the Radcliffe Library, Oxford; and sixteen diagrams taken from the best sources. In the descriptions, which serve as comments on these figures, there is necessarily at times some amount of repetition of what has been gone over in the previous part. Nobody, however, who knows how much the impressions of facts upon the mind are deepened by their being presented in different manners, will regret this. The facts of anatomy, as every teacher or learner of it knows, have to be reiterated many times before they become retained.

A certain amount of preliminary knowledge is necessary before this book, or indeed before any book on comparative anatomy, can be beneficially studied. It is not much. One session's steady work will give any average student a fair knowledge of human osteology and visceral anatomy, and then he will be prepared to enter with advantage on such a study of comparative anatomy as Professor Rolleston has here so admirably sketched out for him.

OTHER WORLDS THAN OURS.*

THE first sentiment of a thoughtful man untrammelled by the influences of doctrinal theology, when he hears the question, "Are the celestial spheres intended as the abode of life?" is one of profound astonishment. The more natural inquiry, it seems to him, would be, "Why should the other worlds not be the seats of living organisms?" and the very question reminds him at once of the littleness of his race, and of the restricted mental capacity which can seriously entertain such a doubt. Imagine a colony of ants, who have raised, what appears to them, a vast monument of their enterprise and industry in the shape of a little mound, upon some islet in a vast lake; and conceive of the complacency with which the antphilosophers will gaze upon the neighbouring islets, from which they are separated by an impassable barrier, and of their grave deliberations as to whether those other vast regions are peopled with beings like themselves, or what can have been the object Nature had in view when she raised up other lands besides their own? This is precisely the position of our philosophers who cling to the idea that

*Other Worlds than Ours: the Plurality of Worlds studied under the Light of Recent Scientific Researches.' By Richard A. Proctor, B.A., F.R.A.S. Longmans, Green, & Co.

ours is the only habitable world, and that the rest are but shining lights placed in the heavens to give us light by night.

If we thought that many of our readers continued to hold this doctrine, we should indeed lay down our pen in despair, and descend to themes which come within the scope of the utilitarian understanding; but thanks to the rapidly advancing strides of science, we may fairly assume that a large proportion of the readers who consult these pages are quite prepared to consider with the author of the work before us, not whether other worlds are the seats of organized existence, but whether we have any, and, if any, what kind of evidence concerning the nature of the living forms which now inhabit, or are destined in future to reside upon, the other celestial spheres.

In considering the question from this point of view, we are compelled still to admit our profound ignorance; but we may do so without shame or humiliation, for in this case it is no longer the unreasoning ignorance of the lower animals-we are no longer antphilosophers-it is the darkness which precedes light; the gloom that is being dispelled, slowly but surely, by the efforts of philosophical research, through that quality of the human mind which distinguishes us from inferior intelligences. We know very little indeed of the conditions of existence in spheres other than our own, and although Mr. Proctor has managed to write a book of more than 300 pages on the subject (a great portion of which, however, deals with matters interesting enough in themselves, but completely alien to the main inquiry), all that has been ascertained with anything approaching to certainty as bearing upon the habitability of the heavenly bodies, might easily be compressed into a dozen sentences. So that if we were strictly to obey the injunction which is given to young lawyers, that before they begin to consider the law in any particular case upon which they are consulted, they should thoroughly master the facts; if, we say, we were to apply this safe method to the question, what kind of beings are living or destined to live upon the heavenly spheres, the consideration of the subject might be long deferred, and we should have to pronounce upon it with great doubt and hesitancy.

Around Mercury there is probably some kind of atmosphere, but the planet is too near the sun to admit of a satisfactory examination with our present philosophical instruments. Venus almost certainly possesses an atmosphere, and the inclination of her axis leads us to infer the existence of seasons.

Mars is the great pièce de résistance in this light intellectual banquet. That planet has almost certainly an atmosphere heavily laden with clouds, two poles similar to our own, capped with snow which encroaches upon and recedes from its more temperate zones according to the seasons of the Martial year of 687 days; those seasons being, like our own, the consequence of an inclination in