and clothing, and for delight. Their evil influence is almost restricted to that of disease germs and poisonous herbs.

Animals likewise furnish food (perhaps to an unwholesome extent); and parts of their bodies are used (sometimes carelessly) in manifold ways. Among those which are domesticated, some, such as canary and parrot, cat and dog, are kept for the pleasure they give to many; others, such as dog, horse, elephant, and falcon, are used in the chase; others, notably the dog, assist in shepherding; horse and ass, reindeer and cattle, camel and elephant, are beasts of burden; others yield useful products, the milk of cows and goats, the eggs of birds, the silk of silkworms, and the honey of bees.

Formerly of much greater importance for good and ill as direct rivals, animals have, through man's increasing mastery of life, become less dangerous and more directly useful. Only in primitive conditions of life and in thinly-peopled territories is something of the old struggle still experienced. Their influence for ill is now for the most part indirect,-on crops and stocks. Parasites are common enough, but rarely fatal. The serpent, however, still bites the heel of progressive man.

Man's relations with living creatures are so close that systematic knowledge about them is evidently of direct use. Indeed it is in practical lore that both botany and zoology have their primal roots, and from these, now much strengthened, impulses do not cease to give new life to science.

If increase of food-supply be desirable, biology has something to say about soil and cereals, about fisheries and oyster-culture. The art of agriculture and breeding has been influenced not a little by scientific advice, though much more by unrationalised experience. If wine be wanted, the biologist has something to say about grafting and the Phylloxera, about mildew and Bacteria. It is enough to point to the succession of discoveries by which Pasteur alone has enriched science and benefited humanity.

But if we take higher ground and consider as an ideal the healthfulness of men, which is one of the most obvious and useful standards of individual and social conduct, the practical justification of biological science becomes even more apparent.

Medicine, hygiene, physical education, and good-breeding (or "eugenics ") are the arts which correspond to the science of biology, just as education is applied psychology, as government is applied sociology, and as many industries are applied chemistry and physics. It would be historically untrue to say that the progress in these arts was due to progress in the parallel sciences; in fact the progressive impulse has often been from art to science. "La pratique a partout devancé la théorie," Espinas says, and all

historians of science would in the main confirm this. But it is also true that science reacts on the arts and sometimes improves them.

There may be peculiar aberrations of the art of medicine due to the progress of the science thereof, but these are because the science is partial, and hardly affect the general fact that scientific progress has advanced the art of healing. The results of science have likewise supplied a basis to the endeavours to prevent disease and to increase healthfulness, not only by definite hygienic practice but perhaps still more by diffusing some precise knowledge of the conditions of health.

The generalisations of biology, realised in men's minds, must in some measure affect practice and public opinion. Spencer's induction that the rate of reproduction varies inversely with the degree of development sheds a hopeful light on the population question; the recognition of the influence which function and surroundings have upon the organism suggests criticism of many modes of economic production; a knowledge of the facts and theory of heredity must have an increasing influence on the art of eugenics. Nor can I believe that the theory of evolution which men hold, granting that it is in part an expression of their life and social environment, does not also react on these.

In short, the direct application of biological knowledge in the various arts of medicine, hygiene, physical education, and eugenics, helps us to perfect our environment and our relations with it, helps us to discover-if not the "elixir vitæ "—some not despicable substitute. And likewise, a realisation of the facts and principles of biology helps us to criticise, justify, and regulate conduct, suggesting how the art of life may be better learned, how human relations may be more wisely harmonised, how we may guide and help the ascent of man.

8. Intellectual Justification of Biology.—But another partial justification of Biology is found in our desire to understand things, in our dislike of obscurities, in our inborn curiosity. There is an intellectual as well as a practical and ethical justification of the study of organic life.

Through our senses we become aware of the world of which we form a part. We cannot know it in itself, for we are part of it and only know it as it becomes part of us. We know only fractions of reality-real at least to us—and these are unified in our experience.

(1) In the world around us we are accustomed to distinguish four orders of facts. "Matter" and "energy" we call those which seem to us fundamental, because all that we know by our senses are forms of these. The study of matter and energy—or perhaps we may say the study of matter in motion-considered apart from

life, we call Physics and Chemistry, of which astronomy, geology, etc., are special departments.

(2) But we also know something about plants and animals, and while all that we know about them is still dependent upon changes of matter and motion, yet we recognise that the activities of the 、 organism cannot at present be expressed in terms of these. Therefore we find it convenient to speak of life as a new reality, while believing that it is the result of some combination of matters and energies, the secret of which is hidden.

(3) But we are also aware of another reality, our own mind. Of this we have direct consciousness and greater certainty than about anything else. And while some would say that what we are conscious of when we think is a protoplasmic change in our brain cells or is a subtle kind of motion, it is truer to say that we are conscious of ourselves. It is our thought that we know, it is our feeling that we feel, and as we cannot explain the thought or the feeling in terms of protoplasm or of motion, we find it convenient to speak of mind as a new reality, while believing it to be essentially associated with some complex activity of protoplasm the secret of which is hidden. For our knowledge of our own mental processes, and of those inferred to be similar in our fellows, and of those inferred to be not very different in intelligent animals, we establish another science of Psychology.

(4) But we also know something about the life of the human society of which we form a part. We recognise that it has a unity of its own, and that its activities are more than those of its individual members added up. We find it convenient to regard society as another synthesis or unity-though less definite than either organism or mind-and to our knowledge of the life and growth of society as a whole, we apply the term sociology. Thus we recognise four orders of facts and four great sciences— 4. Society Sociology.

3. Mind

2. Life

1. Matter and Energy

Psychology.
Biology.

Physics and Chemistry.

Each of these sciences is dependent upon its predecessor. The student of organisms requires help from the student of chemistry and physics; mind cannot be discussed apart from body; nor can society be studied apart from the minds of its component members. Each order of realities we may regard as a subtle synthesis of those which we call simpler. Life is a secret synthesis of matter and energy; mind is a subtle form of life; society is a unity of minds.

But it must be clearly recognised that the "matter and energy" which we regard as the fundamental realities are only known to us

And

through what is for us the supreme reality-ourselves—mind. as in our brain activity we know matter and energy as thought, I have adopted throughout this book what may be called a monistic philosophy.

Having recognised the central position of Biology among the other sciences, we have still to inquire what its task precisely is.

Our scientific data are (1) the impressions which we gather through our senses about living creatures, and (2) the deductions which we directly draw in regard to these. Our scientific aim is to arrange these data so that we may have a mental picture of the life around us, so that we may be better able to understand what that life is, and how it has come to be what it seems to be. Pursuing what are called scientific methods, we try to make the world of life and our life as organisms as intelligible as possible. We seek to remove obscurities of perception, to make the world translucent, to make a working thought-model of the world.

But we are apt to forget how ignorant we are about the realities themselves, for all the time we are dealing not with realities, but with impressions of realities, and with inferences from these impressions. On the other hand, we are apt to forget that our deep desire is not merely to know, but to enjoy the world, that the heart of things is not so much known by the man as it is felt by the child.

APPENDIX II

SOME OF THE "BEST BOOKS" ON ANIMAL LIFE

To recommend the "best books" on any subject is apt to be like prescribing the "best diet." Both depend upon age, constitution, and opportunities. The best book for me is that which does me most good, but it may be tedious reading for you. Moreover, books are often good for one purpose and not for another; that which helps us to realise the beauty and marvel of animal life may be of little service to those who are preparing for any of the numerous examinations in science. But the greatest difficulty is that we are often too much influenced by contemporary opinion, so that we lose our power of appreciating intellectual perspective.

The best way to begin the study of Natural History is to observe animal life, but the next best way is to read such accounts of observation and travel as are to be found in the works of Gilbert White, Thoreau, Richard Jefferies, and John Burroughs, or in Bates's Naturalist on the Amazons, Belt's Naturalist in Nicaragua, and Darwin's Voyage of the "Beagle." Sooner or later the student will seek more systematic books, but it is not natural that he should begin with a text-book of elementary biology.

In introducing you to the literature devoted to the study of animals, I shall avoid the bias of current opinion by following the history of zoology. I shall first name some of the more technical books; secondly, some of the more popular; thirdly, some of the more theoretical. If I may make the distinction, I shall first mention books on zoology, secondly those on natural history, thirdly those on biology.

A. Zoology.

(1) We can form a vivid conception of the history of zoology by comparing it with our own. In our childhood we knew and