A Course of Elementary Instruction in Practical Biology. By T. H. Huxley, LL.D., F.R.S., assisted by H. N. Martin, M.A., M.D., D.Sc., F.R.S. Revised Edition. Extended and Edited by G. B. Howes, Assistant Professor of Zoology, Normal School of Science and Royal School of Mines; and D. H. Scott, M.A., Ph.D., Assistant Professor of Botany, Normal School of Science and Royal School of Mines. With a Preface by Prof. Huxley, F.R.S. ([London: Macmillan and Co., 1888.)
The appearance of the first edition of "A Course of Elementary Instruction in Practical Biology" in 1875 marked an epoch in biological education. The great effects which the doctrine of evolution had been gradually producing in the general system of biological education were then set forth, and widely extended, by means of a clearly written volume containing an account of thirteen types of the organic kingdom. On the appearance of a greatly extended edition of the work, it may not be out of place to say a few words upon the "type-system" of biological education for which the book in its earlier form has done so much. The immense educational success of the work may perhaps be best judged by the fact that, since its publication, an ever-increasing demand has rendered necessary the production of quite a number of new books following the "type-system," and constructed on an identical plan, but dealing with other forms of life.
The important changes in teaching which have followed these publications are seen in the far smaller amount of systematic and classificatory work which is now imposed upon beginners, and its replacement by the acquisition of a thorough knowledge of well-selected types. Remembering that classifications are no more than a condensed abstract of the opinion of the day upon the relative affinities of organic forms, it is clear that no one of the suggested schemes of arrangement can be regarded as real, except as perhaps expressing in the best way the results of a limited state of knowledge. We know that opinion on the subject of affinity has greatly changed in the past, and as long as new facts are revealed by biological research, so long will opinion continue to change in the future. From its necessarily shifting character, and from the fact that the teacher cannot fairly insist upon the accuracy of its conclusions, classificatory biology is eminently unsuited to the needs of a beginner. And there is also another reason, in that classification, if properly taught, is far too advanced a subject to be made an element in early education. If classification is the concise expression of biological opinion, it should nevertheless represent an opinion arrived at after the consideration of all the facts and arguments which bear upon the question. The true and only vindication for any suggested modification of existing schemes of affinity must lie in the decided proofs of a better accordance with existing facts. Whoever suggests a modification is under a great responsibility, for, if the alteration is not an improvement, it will certainly be pernicious in adding to our present state of confusion. It is to be hoped that the whole subject will be treated in a more serious spirit in the future than has been accorded to it in the past.
If, then, classification must be dethroned from the high educational position it has held for so long, and which it still maintains to a considerable extent in botanical teaching, what is to be put in its place? Under the type-system a beginner is set to acquire a thorough knowledge of certain central forms of life, each of which is an example of, and a key to, the understanding of an important organic group. At first the types only represent the very largest groups, such as the sub-kingdoms, so that the amount of implied classification is extremely small. As the student progresses, the number of types increases, and the less important organic groups are represented, so that at the end of his course the advanced student finds himself a master of the solid framework of classification, and then the filling in of the details can be carried on in an intelligent and satisfactory manner. It is at this advanced stage of education that advantage can be gained by means of the celebrated "Hunterian system." The comparative study of long series of homologous structures, considered out of relation to the organisms in which they occur, can only confuse the beginner who is not well acquainted with the organisms themselves. But just as the type system prepares the way for, and in fact culminates in, all that is educationally important in classification, so, when a large number of types has been thoroughly learnt, and the varied relations of organ to organ, and of isolated structure to the whole organism, have been grasped in very many instances, then, and not till then, can great advantage be gained by the Hunterian method. And the extensive use of this system will be wisely postponed to a very late period; in fact, until the student is beginning to make use of the training which he has received in the wide fields of biological research. The Hunterian system must always form the backbone of a large part of biological research, although it would be most unwise to make it a fundamental part of biological education. It must, however, be conceded that there are certain systems of structures (such as the osteological and dental systems) which especially lend themselves to this mode of teaching, but on account of this very facility such subjects are liable to assume too great a relative importance in biological training.
One incidental, but by no means necessary or even natural, result of the prevalence of the type-system is to be greatly deplored. This result, which is especially found among students of botany, follows from the habit of rejecting the good as well as the bad points in a disused system. Just as the introduction of section-cutting has led to a too great neglect of dissection and the examination of solid structures, so the prevalence of the type-system seems to threaten the existence of the field naturalist and botanist. Those who follow the old, and, upon the whole, the very foolish system of botanical education which a few years ago was the only system taught, have at least one great advantage: they have keen and intelligent interest in any country walk, while if they possess a little originality and perseverance, they can contribute something towards the solution of some of the most difficult biological problems. But it is not at all uncommon for the successful student of the newer  system to speak of field botany with utter contempt, as a subject unworthy of notice. This is a very unfortunate thing, for there are many most interesting questions which can only be settled by field-observation; and field-observation is in itself a most important, and at the same time a most enjoyable, side of biological training. The same contrast also holds, although to a less extent, on the zoological side. It is much to be hoped that we may be able to correct this great error which has unfortunately attended a healthy, and, upon the whole, highly beneficial educational reaction. It is to be observed that the excellent general descriptions of the types which form so important a feature of the work are in every way calculated to avert this error.
The most striking thing in the revised form of "Practical Biology" is the reversal of the old arrangement, so that the student is now led to begin with a Vertebrate type, and from this to work his way down to the lowest forms of life, and from these, again, upwards to a type of the flowering-plants. There is little doubt that such a change will be met by conflicting criticisms. I believe, however, that the majority of those who have had the widest experience of biological teaching, and especially those who have instructed students in the first use of the microscope, will heartily agree with Prof Huxley's defence of the alteration, in the preface to the revised edition. The process by which a student first learns to see with the microscope is almost like the education of a new sense-organ suddenly conferred upon a mature organism. We know that under such circumstances it would be a very long time before the impressions conveyed by the new organ could be harmonized with the well-known experiences resulting from the stimulation of other organs. Accustomed to judge of the shapes of objects by their appearance in three dimensions, the student is suddenly provided with a field of vision in which shapes have to be nearly always inferred from the appearance of solid three-dimensional objects when seen under conditions which prevent them from being examined in more than two dimensions at any one time. For it is a long time before the student can accustom himself, by focussing at successive depths, and by making the most of the limited third dimension of depth which the high powers of the microscope provide, to judge accurately of the forms of objects. And the novel conditions under which a student sees with the microscope effectually prevent him from making the best of the impressions he receives. Thus, if the section of a solid object presented the appearance of a circle 1 inch in diameter, and if two other sections at right angles to each other and to the first section presented the appearance of a rectangular figure 3 feet by 1 inch, nearly everyone would readily infer that the shape was that of a cylinder 3 feet long by 1 inch in diameter. But precisely similar data, when presented in the field of the microscope, do not readily lead the student to any definite conclusions as to the forms of objects, and in reality a long course of discipline is necessary in order to make him form any clear conception of the actual shape of the object at which he is looking. I therefore think that it is expedient to begin the course of biological teaching with organisms which only require the use of a microscope for the/ investigation of part of their structure, and thus to gradually work downwards to the minutest organisms, in which the whole investigation depends upon high microscopic powers. Thus the gradual training in the use of the microscope will proceed parallel with its gradually increasing necessity.
The addition of the earthworm, the snail, and of Spirogyra is a great improvement upon the former edition of the work. If a choice were necessary, the snail is in many respects a more suitable type than the Anodon. In spite of the greater structural simplicity of the latter form, the anatomical details are more difficult to demonstrate by dissection and more difficult to see when dissected than those of the snail. This objection to the Anodon of course only applies to its selection in preference to the snail in the earlier edition; it is in every way desirable that the Lamellibranchs, as well as the Gastropods, should be represented by a well-known type. These newly added types and the additions to the descriptions of those in the previous edition, and to the practical directions, so increase the size of the volume that it contains almost exactly twice the number of pages present in the earlier form of the work. The practical directions given in the appendix appear to be excellent, and to contain in a very small compass an immense amount of information upon the most recent and approved methods. There are a few slips and indefinite statements which should be modified in succeeding editions, which will doubtless be called for at no distant date.
Thus, on p. 383 we are told that one or two per cent. of the sugar is unaccounted for in fermentation; but for the rest it is only loosely stated that the greater part is resolved into carbonic anhydride and alcohol and a small part into glycerine and succinic acid. On pp. 384 and 386 it would be well to represent the numerical proportions of the formulæ by the same method. On p. 462 it is wrongly stated that the cotyledons become green in the type selected. They are in reality hypogeal.. On p. 467 no phosphorus is mentioned ¹n the culture solution in which it is stated that the bean-plant will grow. It should read: "potassium phosphate, iron sulphate." instead of "potassium and iron sulphate." In the note on p. 475, "discolour" is used for "decolorize." On p. 483 the student is advised to procure 2 ounces of microscopic slides and half a gross of cover-slips!
Such slight errors can easily be put right, and they would in most cases be detected by the student in reading the book for the first time. They cannot be considered as seriously detracting from so excellent a book, and one which, in the extreme clearness of its style. is so admirably adapted to the needs of the beginner.
C. Blinderman & D. Joyce