This Magazine is published bi-monthly, and is conducted by a Com- J. W. DAWSON, LL.D., F.R.S., Principal of McGill College. T. STERRY HUNT, A.M., F.R.S., Chemist to Geological Survey of Cana la. Elementary views of the Classification of Animals; By J. W. On the Occurrence of Pieris Rape in Canada; By G. J. THE CANADIAN NATURALIST, SECOND SERIES. ELEMENTARY VIEWS OF THE CLASSIFICATION OF ANIMALS. By J. W. DAWSON, LL.D. F.R.S. [The matter of the following pages has been prepared principally for the benefit of students, who are in general much more apt to learn names and details than to attain to general views. It is introductory to the printed synopsis of lectures which I annually prepare for my classes, and is now published under the impression. that, though but elementary and general, the views which it contains may prove interesting to naturalists, and useful to some of those who may be struggling with the difficulties incident to the study of zoology under the heterogeneous methods of classification. which are found in most elementary books. Should time permit, it may be followed by illustrations of the details of some of the classes and orders of animals. The writer acknowledges his obligations, as sources of recent information, to Agassiz's Essay on Classification, Dana's Remarks on the Classification of Animals based on Cephalisation, and Huxley's Lectures on Classification, though he cannot follow throughout the systems of any of these authors.] 1. INTRODUCTORY REMARKS. No subject is at present more perplexing to the practical zoölogist or geologist, and to the educator, than that of zoological classification. The subject in itself is very intricate, and the views given as to certain groups by the most eminent naturalists so conflicting, that the student is tempted to abandon it in despair, as incapable of being satisfactorily comprehended. The reasons of this, it seems to the writer, are twofold. First, zoology is so extensive, that it has become divided into a number of subordinate branches, the cultivators of which attach an exagVOL. I. No. 4. gerated value to their own specialties, and are unable to appreciate those of others. Thus we find naturalists subdividing one group more minutely than others, or raising one group to a position of equivalency with others, to which, in the opinion of the students of these others, it is quite subordinate. So also we have some zoologists basing classification wholly on embryology or on mere anatomical structure, or even on the functions of some one class of organs. Secondly, there is a failure to perceive that, if there is any order in the animal kingdom, some one principle of arrangement must pervade the whole; and that our arrangement must not be one merely of convenience, or of a desultory and uncertain character, but uniform and homogeneous. The writer of these pages does not profess to be in a position to escape from these causes of failure; but as a teacher of some experience, and as a student of certain portions of the animal kingdom, he has endeavoured carefully to eliminate from his own views the prejudices incident to his specialties, and to take a general view of the subject; and is therefore not without hope that the results at which he has arrived may be found useful to the young naturalist. Classification in any department of Natural History is the arranging of the objects which we study in such a manner as to express their natural relationship. In other words, we endeavour in classification to present to our minds such a notion of the resemblances and differences of objects as may enable us to understand them, not merely as isolated units, but as parts of the system of nature. Without such arrangement there could be no scientific knowledge of nature, and our natural history would be merely a mass of undigested facts. At first sight, and to a person knowing only a few objects, such arrangement may appear easy; but in reality it is encompassed with difficulties, some of which have not been appreciated by the framers of systems. The more important of these difficulties we may shortly consider. 1. There are in the animal kingdom a vast number of kinds or species. To form a perfect classification it would be necessary to know the characters or distinctive marks of all these species. To make even a tolerable approximation to a good system, requires an amount of preparatory labour which can be estimated only by those who have carefully worked up at least a few species in these respects. 2. So soon as we have ascertained the characters of a considerable number of species, we find that in their nearest resemblances these do not constitute a linear series, but arrange themselves in groups more or less separated from each other like constellations in the heavens, and having relationships tending with more or less force in different directions. This not only introduces complexity into our systems, but renders it impossible to represent them adequately in written or spoken discourse, or even by tables or diagrams. We think and speak of things in series, but nature's objects are not so arranged, but in groups radiating from each other like the branches of a tree; and our imperfect modes of thought and expression are severely tested in the attempt to understand nature, or to convey ideas of classification to the minds of others. 3. The considerations above stated oblige us to enquire what leading characters we may take as the principal thread of our arrangement, so as to make this as natural as possible and at the same time intelligible. It is simplest to take only one obvious character, as if for example we were to arrange all animals according to their colour or to the number of their limbs; but the greater the number of characters we can use, or the more completely we can represent the aggregate of resemblances and differences, the more natural will our arrangement be, and consequently also the more scientific and useful. In attempting to weigh the several characters presented by any object, we find some that are of leading importance, others that are comparatively unimportant, though still not to be neglected; and we find that some indicate grades of complexity, others are connected with adaptations to certain uses, and others indicate plan of construction. Due weight must be given to all these kinds and degrees of characters. It is perhaps in the proper. estimation and value of their relative importance and different modes of application that the greatest failures have been made. Keeping in view these difficulties of the subject, we may now proceed to the consideration of the more elementary of the groups in which we arrange animals. 2. THE SPECIES IN ZOOLOGY. We cannot consider the animals with which we are familiar without perceiving that they constitute kinds or Species, which do not appear to graduate into each other, and which can be distin |