Consciousness.—It may be well here to refer to one other factor in the problem, because it has somewhat recently been brought into prominence. This factor is consciousness on the part of the animal. Among plants and the lower animals this factor can have no significance, but consciousness certainly occurs among the higher animals. Just when or how it appeared are questions which are not answered, and perhaps never will be. But consciousness, after it had once made its appearance, became a controlling factor in the development of the machine. It must not be understood by this that animals have had any consciousness of the development of their body, or that they have made any conscious endeavours to modify its development. This has not always been understood. It has been frequently supposed that the claim that consciousness has an influence upon the development of an animal means that the animal has made conscious efforts to develop in certain directions. For example, it has been suggested that the tiger, conscious of the advantage of being striped, had a desire to possess stripes, and the desire caused their appearance. This is absurd. Consciousness has been a factor in the development of the machine, but an indirect one. Consciousness leads to effort, and effort has a direct influence in development. For example, an animal is conscious of hunger, and this leads to efforts on his part to obtain food. His efforts to obtain food may lead to migration or to the adoption of new kinds of food or to conflicts with various kinds of rivals, and all of these efforts are potent factors in determining the direction of development. Consciousness, again, may lead certain animals to take pleasure in each other's society, or to recognize that in mutual association they have protection against common enemies. Such a consciousness will give rise to social habits, and social habits are a very potent factor in determining the direction in which the inherited variations will tend; not, perhaps, because it effects the variations themselves, but rather because it determines which variations among the many shall be preserved and which rejected by natural selection. Consciousness may lead the antelope to recognize that he has no chance in a combat with a lion, and this will induce him to flee. The habit of flight would then develop the power of flight, not because the antelope desired such power, but because the animals with variations which gave increased power of flight would be the ones to escape the lion, while the slower ones would die without offspring. Thus consciousness would indirectly, though not directly, result in the lengthening of the legs of the animal and in the strengthening of his running muscles. Beyond a doubt this factor of consciousness has been a factor of no little moment in the development of the higher types of organic machines. We can as yet only dimly understand its action, but it must hereafter be counted as one of the influences in the evolution of the living machine.

But, after all, these are only questions of the method of the action of certain well demonstrated, fundamental factors. Whether by natural selection, or by the inheritance of acquired characters produced by the environment, or whether by the effect of isolation of groups of individuals, the machine building has always been produced in the same way. A machine, either through the direct influence of the environment, or as a result of sexual combination of germ plasm, shows a variation from its parents. This variation proves of value to its possessor, who lives and transmits it permanently to posterity. Thus step by step, one part is added to another, until the machine has grown into the intricately adapted structure which we call the animal or plant. This has been nature's method of building machines, all based upon the three properties possessed by the living cell—reproduction, variation, and heredity.

Summary of Nature's Power of Building Machines.—Let us now notice the position we have reached. Our problem in the present chapter has been to find out whether nature possesses forces adequate to explain the building of machines with their parts accurately adapted to each other so as to act harmoniously for certain ends. Astronomy has shown that she has forces for the building of worlds; geology, that she has forces for making mountain and valley; and chemistry, that she has forces for building chemical compounds. But the organism is neither a world, nor a mass of matter, nor a chemical compound. It is a machine. Has nature any forces for machine building? We have found that by the use of the three factors, reproduction, variation, and heredity, nature is able to produce a machine of ever greater and greater complexity, with the parts all adapted to each other. Now the difference between a machine and a mass of matter is simply in the adaptation of parts to act harmoniously for definite ends. Hence if we are allowed these three factors, we can say that nature does possess forces adequate to the manufacture of machines. These forces are not chemical forces, and the construction of the machine has thus been brought about by forces entirely different from those which produced the chemical molecule.

But we have plainly not reached the bottom of the matter in our attempt to explain the machinery of living things. We have based the whole process upon three factors. Reproduction, variation, and heredity are the properties of all living matter; but they are not, like gravity and chemism, universal forces of nature. They occur in living organisms only. Why should they occur in living organisms, and here alone? These three properties are perhaps the most marvellous properties of nature; and surely we have not finished our task if we have based the whole process of machine building upon these mysterious phenomena, leaving them unintelligible. We must therefore now ask whether we can proceed any farther and find any explanation of these fundamental powers of the living machine.

It must be confessed that here we are at present forced to stop. We can proceed no further with any certainty, or even probability. We may say that variation and heredity are only phases of reproduction, and reproduction is a property of the living cell. We may say that this power of reproduction is dependent upon the power of assimilation and growth, for cell division is a result of cell growth. We may further say that growth and assimilation are chemical processes resulting from the oxidation of food, and that thus all of these processes are to be reduced to chemical forces. In this way we may seem to have a chemical foundation for life phenomena. But clearly this is far from satisfactory. In the first place, it utterly fails to explain why the living cell has these properties, while no other body possesses them, nor why they are possessed by living protoplasms alone, ceasing instantly with death. Indeed it does not tell us what death can be. Secondly, it utterly fails to explain the marvels of cell division with resulting hereditary transmission. For all this we must fall back upon the structure of protoplasm, and say that the cell machinery is so adjusted that the machine, when acting as a whole, is capable of transforming the energy of chemical composition in certain directions. These fundamental properties are then the properties of the cell machine just as surely as printing is the property of the printing press. We can no more account for the life phenomena by chemical powers than we can for printing by chemical forces manifested in the burning of the coal in the engine room. To be sure, it is the chemical forces in the engine room that furnishes the energy, but it is the machinery of the press that explains the printing. So, while chemical forces supply life energy, it is the cell machinery that must explain the fundamental living factors. So long as this machine is intact it can continue to run and perform its duties. But it is a very delicate machine and is easily broken. When it is broken its activities cease. A broken machine can not run. It is dead. In short, we come back once more to the idea of the machinery of protoplasm, and must base our understanding of its properties upon its structure.

It is proper to state that there are still some biologists who insist that the ultimate explanation of protoplasm is purely chemical and that life phenomena may be manifested in mixtures of compounds that are purely physical mixtures and not machines. It is claimed that much of this cell structure described above is due to imperfection in microscopic methods and does not really exist in living protoplasm, while the marvellous activities described are found only in the highly organized cell, but do not belong to simple protoplasm. It is claimed that simple protoplasm consists of a physical mixture of two different compounds which form a foam when thus mixed, and that much of the described structure of protoplasm is only the appearance of this foam. This conception is certainly not the prevalent one to-day; and even if it should be the proper one, it would still leave the cell as an extremely complicated machine. Under any view the cell is a mechanism and must be resolved into subordinate parts. It may be uncertain whether these subordinate parts are to be regarded simply as chemical compounds physically mixed, or as smaller units each of which is a smaller mechanism. At all events, at the present time we know of no such simple protoplasm capable of living activities apart from machinery, and the problem of explaining life, even in the simplest form known, remains the problem of explaining a mechanism.

The Origin of the Cell Machine.—We have thus set before us another problem, which is after all the fundamental one, namely, to ask whether we can tell anything of nature's method of building the protoplasmic machine. The building of the higher animal and plant, as we have seen, is the result of the powers of protoplasm; but protoplasm itself is a machine. What has been its history?

We must first notice that no notion of chemical evolution helps us out. It has been a favourite thought with some that the origin of the first living thing was the result of chemical evolution. As the result of physical forces there was produced, from the original nebulous mass, a more and more complicated system until the world was formed. Then chemical phenomena became more and more complicated until, with the production of more and more complicated compounds, protoplasm was finally produced. A few years ago, under the impulse of the idea that protoplasm was a compound, or at least a simple mixture of compounds, this thought of protoplasm as the result of chemical evolution was quite significant. Physical forces, chemical forces, and vital forces, explain successively the origin of worlds, protoplasm, and organisms. This conception has, however, no longer much significance. We know of no such living chemical compound apart from cell machinery. A new conception of protoplasm has arisen which demands a different explanation of its origin. Since it is a machine rather than a compound, mechanical rather than chemical forces are required for its explanation.

Have we then any suggestion as to the method of the origin of this protoplasmic machine? Our answer must, at the present, be certainly in the negative. The complexity of the cell tells us plainly that it can not be the ultimate living substance which may have arisen from chemical evolution. It is made up of parts delicately adapted to act in harmony with each other, and its activity depends upon the relation of these parts. Whatever chemical forces may have accomplished, they never could have combined different bodies into linin, centrosomes, chromosomes, etc., which, as we have seen, are the basis of cell life. To account for this machine, therefore, we are driven to assume either that it was produced by some unknown intelligent power in its present condition of complex adjustment, or to assume that it has had a long history of building by successive steps, just as we have seen to be the case with the higher organisms. The latter assumption is, of course, in harmony with the general trend of thought. To-day protoplasm is produced only from other protoplasm; but, plainly, the first protoplasm on the earth must have had a different origin. We must therefore next look for facts which will enable us to understand its origin. We have seen that the animal and plant machines have been built up from the simple cell as the result of its powers acting under the ordinary conditions of nature. Now, in accordance with this general line of thought, we shall be compelled to assume that previous to the period of building machinery which we have been considering, there was another period of machine building during which this cell machine was built by certain natural forces.

But here we are forced to stop, for nothing which we yet know gives even a hint as to the method by which this machine was produced. We have, however, seen that there are forces in nature efficient in building machines, as well as those for producing chemical compounds; and this, doubtless, suggests to us that there may be similar forces at work in building protoplasm. If we can find natural forces by which the simplest bit of living matter can be built up into a complicated machine like the ox, with its many delicately adjusted parts, it is certainly natural to imagine that the same forces may have built this simpler machine with which we started. But such a conclusion is for a simple reason impossible. We have seen that the essential factor in this machine building is reproduction, with the correlated powers of variation and heredity. Without these forces we could not have advanced in this machine building at all. But these properties are themselves the result of the machinery of protoplasm. We have no reason for thinking that this property of reproduction can occur in any other object in nature except this protoplasmic machine. Of course, then, if reproduction is the result of the structure of protoplasm we can not use this factor in explaining the origin of this protoplasm. The powers of the completed machine can not be brought forward to account for its origin. Thus the one fundamental factor for machine building is lacking, and if we are to explain nature's method of producing protoplasm from simpler structures, we must either suppose that the parts of the cell are capable of reproduction and subject to heredity, or we must look for some other method. Such a road has however not yet been found, nor have we any idea in what direction to look. But the fact that nature has methods of machine building, as we have seen, may hold out the possibility that some day we may discover her method of building this primitive living machine, the cell.

It is useless to try to go further at present. The origin of living matter is shrouded in as great obscurity as ever. We must admit that the disclosures of the modern microscope have complicated rather than simplified this problem. While a few years ago chemists and biologists were eagerly expecting to discover a method of manufacturing a bit of living matter by artificial means, that hope has now been practically abandoned. The task is apparently hopeless. We can manipulate chemical forces and produce an endless series of chemical compounds. But we can not manipulate the minute bits of matter which make up the living machine. Since living matter is made of the adjustment of these microscopic parts of matter, we can not hope to make a bit of living matter until we find some way of making these little parts and adjusting them together. Most students of protoplasm have therefore abandoned all expectation of making even the simplest living thing. We are apparently as far from the real goal of a natural explanation of life as we were before the discovery of protoplasm.

General Summary.—It is now desirable to close this discussion of seemingly somewhat unconnected topics by bringing them together in a brief summary. This will enable us to see more clearly the position in which science stands to-day upon this matter of the natural explanation of living phenomena, and to picture to ourselves more concisely our knowledge of the living machine.

The problem we have set before us is to find out to what extent it is possible to account for vital phenomena by the application of ordinary natural laws and forces, and therefore to find out whether it is necessary to assume that there are forces needed to explain life which are different from those found in other realms of nature, or whether vital forces are all correlated with physical forces. It has been evident at a glance that the living body is a machine. Like other machines it consists of parts adjusted to each other for the accomplishment of definite ends, and its action depends upon the adjustment of its parts. Like other machines, it neither creates nor destroys energy, but simply converts the potential energy of its foods into some form of active energy, and, like other machines, its power ceases when the machine is broken.

With this understanding the problem clearly resolved itself into two separate ones. The first was to determine to what extent known physical and chemical laws and forces are adequate to an explanation of the various phenomena of life. The second was to determine whether there are any known forces which can furnish a natural explanation of the origin of the living machine. Manifestly, if the first of these problems is insolvable, the second is insolvable also.

In the study of the first problem we have reached the general conclusion that the secondary phenomena of life are readily explained by the application of physical and chemical forces acting in the living machine. These secondary phenomena include such processes as the digestion and absorption of food, circulation, respiration, excretion, bodily motion, etc. Nervous phenomena also doubtless come under this head, at least so far as concerns nervous force. We have been obliged, however, to exclude from this correlation the mental phenomena. Mental phenomena can not as yet be measured, and have not yet been shown to be correlated with physical energy. In other words, it has not yet been proved that mental force is energy at all; and if it is not energy, then of course it can not be included in the laws which govern the physical energy of the universe. Although a close relation exists between physical changes in the brain cells and mental phenomena, no further connection has yet been drawn between mental power and physical force. All other secondary phenomena, however, are intelligently explained by the action of natural forces in the machinery of the living organism.

While we have thus found that the secondary phenomena of life are intelligible as the result of the structure of the machine, certain other fundamental phenomena have been constantly forcing themselves upon our attention as a foundation of these secondary activities. The power of contraction, the power of causing certain kinds of chemical change to occur which result in metabolism, the property of sensibility, the property of reproduction—these are fundamental to all living activity, and are, after all, the real phenomena which we wish to explain. But these are not peculiar to the complicated machines. We can discard all the apparent machinery of the animal or plant and find these properties still developed in the simplest bit of living matter. To learn their significance, therefore, we have turned to the study of the simplest form of matter in which these fundamental properties are manifested. This led us at once to the study of the so-called protoplasm, for protoplasm is the simplest known form of matter that is alive. Protoplasm itself at first seemed to be a homogeneous body, and was looked upon as a chemical compound of high complexity. If this were true its properties would depend upon its composition and would be explained by the action of chemical forces. Such a conception would have quickly solved the problem, for it would reduce living properties to chemical powers. But the conception proved to be delusive. Protoplasm, at least the simplest form known to possess the fundamental life properties, soon showed itself to be no chemical compound, but a machine of wonderful intricacy.

The fundamental phenomena of life and of protoplasm have proved to be both chemical and mechanical. Metabolism is the result of the oxidation of food, and motion is an instance of transference of force. Our problem then resolved itself into finding the power that guides the action of these natural forces. Food will not undergo such an oxidation except in the presence of protoplasm, nor will the phenomena of metabolism occur except in the presence of living protoplasm. Clearly, then, the living protoplasm contains within itself the power of guiding this play of chemical force in such a way as to give rise to vital phenomena, and our search must be not for chemical force but for this guiding principle. Our study of protoplasm has told us clearly enough that we must find this guiding principle in the interaction of the machinery within the protoplasm. The microscope has told us plainly that these fundamental principles are based upon machinery. The cell division (reproduction) is apparently controlled by the centrosomes; the heredity by the chromosomes; the constructive metabolism by the nucleus in general, while the destructive metabolism is also seated in the cell substance outside the nucleus. Whether these statements are strictly accurate in detail does not particularly affect the general conclusion. It is clearly enough demonstrated that the activities of the protoplasmic body are dependent upon the relation of its different parts. Although we have got rid of the complicated machinery of the organism in general, we are still confronted with the machinery of the cell.

But our analysis can not, at present, go further. Our knowledge of this machine has not as yet enabled us to gain any insight as to its method of action. We can not yet conceive how this machine controls the chemical and physical forces at its disposal in such a way as to produce the orderly result of life. The strict correlation between the forces of the physical universe and those manifested by this protoplasm tells us that a transformation of energy occurs within it, but of the method of that transformation we as yet know nothing. Irritability, movement, metabolism, and reproduction appear to be not chemical properties of a compound, but mechanical properties of a machine. Our mechanical analysis of the living machine stops short before it reaches any foundation in the chemical forces of nature.

It is thus clearly apparent that the phenomena of life are dependent upon the machinery of living things, and we have therefore the second question of the origin of this machinery to answer. Chemical forces and mechanical forces have been laboriously investigated, but neither appear adequate to the manufacture of machines. They produce only chemical compounds and worlds with their mountains and seas. The construction of artificial machines has demanded intelligence. But here is a natural machine—the organism. It is the only machine produced by natural methods, so far as we know; and we have therefore next asked whether there are, in nature, simple forces competent to build machines such as living animals and plants?

In pursuance of this question we have found that the complicated machines have been built out of the simpler ones by the action of known forces and laws. The factors in this machine building are simply those of the fundamental vital properties of the simplest protoplasmic machine. Reproduction, heredity, and variation, acting under the ever-changing conditions of the earth's surface, are apparently all that are needed to explain the building of the complex machines out of the simpler ones. Nature has forces adequate to the building of machines as well as forces adequate to the formation of chemical compounds and worlds.

But here again we are unable to base our explanation upon chemical and physical forces. Reproduction, heredity, and variation are properties of the cell machine, and we are therefore thrown back upon the necessity of explaining the origin of this machine. Can we find a mechanical or chemical explanation of the origin of protoplasm? A chemical explanation of the cell is impossible, since it is not a chemical compound, but a piece of mechanism. The explanation given for the origin of animals and plants is also here apparently impossible. The factors upon which that explanation depended are factors of this completed machine itself, and can not be used to explain its origin. We are left at present therefore without any foundation for further advance. The cells must have had a history of construction, but we do not as yet conceive any forces which may be looked upon as contributing to that history. Whether life phenomena can be manifested by any mixture of compounds simpler than the cell we do not yet know.

The great problems still remaining for solution, which have hardly been touched by modern biology in all its endeavours to find a mechanical explanation of the living machine, are, therefore, three. First, the relation of mentality to the general phenomena of the correlation of force; second, the intelligible understanding of the mechanism of protoplasm which enables it to guide the blind chemical and physical forces of nature so as to produce definite results; third, the kind of forces which may have contributed to the origin of that simplest living machine upon whose activities all vital phenomena rest—the living cell.



INDEX.

A.

Absorption of food, 20.

Acquired characters, inheritance of, 164, 165, 166, 167, 171. —variations, 159, 160.

Amoeba, 73.

Anatomical evidence for evolution, 142.

Aquacity, 80.

Arm compared with wing, 144.

Aristotle, 1.

Assimilation, 80, 124, 149, 176.

Asters of dividing cells, 98.

B.

Barry, 63, 64.

Bathybias, 84.

Biology a new science, 1, 5, 15.

Blood, 35, 36, 38, 69, 73.

Blood-vessels, 35, 36.

Body as a machine, 22, 25, 49.

Bone cells, 69.

Building of the living machine, 131, 134, 136, 137, 167, 175, 180.

C.

Cartilage cells, 68. Cell as a machine, 126, 128. —description of, 69. —division, 95, 96, 101. —discovery of, 58. —doctrine, 60. —substance, 65, 125.

Cells, 56, 84, 86, 118, 119.

Cellular structure of organisms, 65.

Cell wall, 64, 72.

Centrosome, 94, 96, 97, 101, 103, 105, 110.

Challenger expedition, 83.

Chemical evolution, 179.

Chemical theory of vitality, 14; of life, 78, 116.

Chemism or mechanism, 57, 176.

Chemistry of digestion, 27, 28; of protoplasm, 76; of respiration, 38.

Chromatin, 92, 94, 96, 102, 149, 153.

Chromosomes, 97, 98, 101, 105, 108, 110, 113, 152.

Circulation, 34.

Colonies of cells, 85.

Comparison of the body and a machine, 22.

Congenital variations, 158, 160, 163; inheritance of, 164.

Connective-tissue cells, 70.

Conservation of energy, 7, 17.

Consciousness as a factor in machine building, 173.

Constructive chemical processes, 50, 51, 52, 124.

Continuity of germ plasm, 155.

Correlation of vital and physical forces, 13, 16, 22, 23, 24, 25.

Cytoblastema. 62.

Cytology, 10.

D.

Darwin, 81.

Death of the cell, 127.

Decline of the reign of protoplasm, 85.

Destructive chemical processes, 50, 51, 52, 125.

Dialysis, 29, 30, 31.

Digestion, 27.

E.

Egg, 103, 120, 152. division of, 63.

Egg, fertilization of, 102.

Embryological evidence for evolution, 140.

Energy of nervous impulse, 43, 54.

Environment, 171.

Evidence for evolution as a method of machine building, 139, 145.

Evolution, 9, 16, 81, 134.

Experiments with developing eggs, 121.

F.

Fat, absorption of, 32.

Female pronucleus, 110.

Fern cells, section of, 67.

Fertilization of the egg, 95, 102; significance of, 112.

Fibres in protoplasm, 87; —in spindle, 98, 101.

Forces at work in machine building, 148, 176, 181.

Formed material, 64.

Free cell formation, 64.

G.

Geological evidence for evolution, 139.

Germ plasm, 154.

H.

Heart as a pump, 35.

Heat, 24, 44, 45.

Heredity, 148, 150, 176; —explanation of, 152.

Hereditary traits, 113, 153.

Historical geology, 6.

History of the living machine, 133, 147.

Horses' toes, loss of, 172.

Huxley, 11, 75, 83, 84.

I.

Irritability, 54.

Isolation, theory of, 170.

K.

Karyokinesis, 96, 101.

Kidneys, 41.

L.

Leaf, section of, 66.

Life the result of a mechanism, 115, 177.

Linin, 92, 103.

Linnaeus, 1.

Lyell, 6.

Lymph, 36, 37.

M.

Machine defined, 20.

Machines the result of mechanical forces, 116.

Male cell, 104, 107.

—— pronucleus, 109.

Maturation of the egg, 104.

Mechanical nature of living organisms, 12.

Mechanical theory of life, 81, 144.

Membrane of the nucleus, 92, 101.

Mental phenomena, 47, 48.

Metabolism, 54.

Microsomes, 87.

Migration, theory of, 170.

Monera, 88.

Movement, 54.

Muscle, 36, 71.

N.

Natural selection, 167.

Nerve-fibre cell, 70.

Nervous energy, 42, 44.

—— system, 41.

New biological problems, 15.

Nucleolus, 65, 92, 94.

Nucleus, 65, 84, 87, 93, 101, 103, 113, 124, 149; formation of new, 101.

—— function of, 89, 90, 95.

—— presence of, 87, 88, 89.

—— structure of, 91.

O.

Organic chemistry, 78.

Organic compounds, artificial manufacture of, 78, 82.

Origin of cell machine, 178, 179, 180.

Origin of life, 81, 182.

Osmosis, 29.

Oxidation, 80, 176.

—— as a vital process, 39, 56.

P.

Philosophical biology, 4.

Physical basis of life, 75.

Polar cells, 107.

Potato, section of cells, 67.

Properties of chemical compounds, 79.

Protoplasm, 14, 74, 82, 83, 84, 114, 115, 179.

—— artificial manufacture of, 82.

—— as a machine, 86, 178.

—— discovery of, 74.

—— nature of, 76.

—— structure of, 86, 87.

Purpose vs. cause, 11, 12.

R.

Reaction against the cell doctrine, 117.

Reign of law, 4.

—— of the nucleus, 91.

—— of protoplasm, 81, 85.

Relationship, significance of, 143.

Removal of waste, 39, 40.

Reproduction, 54, 80, 124, 148, 176; —rapidity of, 149.

Respiration, 37.

Reticulum of cell, 87; —of nucleus, 92.

Root tip, section of, 66.

S.

Schultze, 74, 75.

Schwann, 61, 62, 72.

Secretion, 39, 40.

Segmentation nucleus, 110.

Sensations, 46.

Separation of chromosomes, 100.

Sexual reproduction, 102.

Spermatozoan, 107, 109, 154.

Splitting of chromosomes, 99.

Spindle fibres, 101.

Struggle for existence, 168.

Summary of Part I, 128.

—— general, 182.

U.

Undifferentiated protoplasm, 83.

Unicellular animals, 71.

Units of vital activity, 53.

Use and disuse, 171, 172.

V.

Variation, 148, 157, 160, 176.

Variation from sexual union, 162.

Variation in germ plasm, 161.

Vegetative functions, 41.

Villi, 31.

Vital force, vitality, 13, 15, 34, 37, 52, 80, 85.

Vital properties, 54; —located in cells, 123.

W.

Wing compared with arm, 144.

Wood cells, 68.

THE END.



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"This is a book which was needed.... Altogether, the book could hardly be better done. It is luminous, lucid, orderly, and temperate. Above all, it is entirely free from personal partisanship. Each chief actor is sympathetically treated, and friendship is seldom or never allowed to overweight sound judgment"—London Academy.

"We can assure the reader that he will find in this work a very useful guide to the lives and labors of leading evolutionists of the past and present. Especially serviceable is the account of Mr. Herbert Spencer and his share in rediscovering evolution, and illustrating its relations to the whole field of human knowledge. His forcible style and wealth of metaphor make all that Mr. Clodd writes arrestive and interesting."—London Literary World.

"Can not but prove welcome to fair-minded men.... To read it is to have an object-lesson in the meaning of evolution.... There is no better book on the subject for the general reader.... No one could go through the book without being both refreshed and newly instructed by its masterly survey of the growth of the most powerful idea of modern times."—The Scotsman.

D. APPLETON AND COMPANY, NEW YORK.

BOOKS ON SOCIAL SCIENCE.

Socialism New and Old.

By Prof. WILLIAM GRAHAM, 12mo. Cloth, $1.75.

"Professor Graham's book may be confidently recommended to all who are interested in the study of socialism, and not so intoxicated with its promises of a new heaven and a new earth as to be impatient of temperate and reasoned criticism."—London Times.

"Professor Graham presents an outline of the successive schemes of three writers who have chiefly influenced the development of socialism, and dwells at length upon the system of Rousseau, that of St. Simon, and on that of Karl Marx, the founder of the new socialism, 'which has gained favor with the working classes in all civilized countries,' which agrees with Rousseau's plan in being democratic, and with St. Simon's in aiming at collective ownership.... The professor is an independent thinker, whose endeavor to be clear has resulted in the statement of definite conclusions. The book is a remarkably fair digest of the subject under consideration."—Philadelphia Ledger.

Dynamic Sociology:

Or, Applied Social Science, as based upon Statical Sociology and the less Complex Sciences. By LESTER F. WARD, A.M. In 2 vols. 12mo. Cloth, $4.00.

"A book that will amply repay perusal.... Recognizing the danger in which sociology is, of falling into the class of dead sciences or polite amusements, Mr. Ward has undertaken to 'point out a method by which the breath of life can be breathed into its nostrils.'"—Rochester Post-Express.

"Mr. Ward has evidently put great labor and thought into his two volumes, and has produced a work of interest and importance. He does not limit his effort to a contribution to the science of sociology.... He believes that sociology has already reached the point at which it can be and ought to be applied, treated as an art, and he urges that 'the State' or Government now has a new, legitimate, and peculiar field for the exercise of intelligence to promote the welfare of men."—New York Times.

Criminal Sociology.

By Prof. E. FERRI. A new volume in the Criminology Series, edited by W. Douglas Morrison, 12mo. Cloth, $1.50.

In this volume Professor Ferri, a distinguished member of the Italian Parliament, deals with the conditions which produce the criminal population, and with the methods by which this anti-social section of the community may be diminished. He divides the causes of crime into two great classes, individual and social. The individual causes consist of physical and mental defects; the social causes consist of social disadvantages of every description. His view is that the true remedy against crime is to remove individual defects and social disadvantages where it is possible to remove them. He shows that punishment has comparatively little effect in this direction, and is apt to divert attention from the true remedy—the individual and social amelioration of the population as a whole.

D. APPLETON AND COMPANY, NEW YORK.



BOOKS FOR NATURE LOVERS.

Insect Life. (New Edition in Colors.)

By JOHN HENRY COMSTOCK, Professor of Entomology in Cornell University. With 12 full-page plates reproducing butterflies and various insects in their natural colors, and with many wood engravings by Anna Botsford Comstock, Member of the Society of American Wood Engravers, 12mo. Cloth, $1.75 net; postage, 20 cents additional.

"The volume is admirably written, and the simple and lucid style is a constant delight.... It is sure to serve an excellent purpose in the direction of popular culture, and the love of natural science which it will develop in youthful minds can hardly fail to bear rich fruit."—Boston Beacon.

Familiar Fish: Their Habits and Capture.

A Practical Book on Fresh-Water Game Fish. By EUGENE MCCARTHY. With an Introduction by Dr. David Starr Jordan, President of Leland Stanford Junior University, and numerous Illustrations, 12mo. Cloth, $1.50.

"One of the handsomest, most practical, most informing books that we know. The author treats his subject with scientific thoroughness, but with a light touch that makes the book easy reading.... The book should be the companion of all who go a-fishing."—New York Mail and Express.

The Art of Taxidermy.

By JOHN ROWLEY, Chief of the Department of Taxidermy in the American Museum of Natural History. Illustrated, 12mo. Cloth, $2.00.

"Mr. Rowley will long be gratefully remembered by taxidermists, amateurs, and others, for the care he has used in thus meeting a long-felt want."—Bangor, Me., Sportsman.

"The book is not an elaborate treatise upon the abstract principles which lie at the foundation of artistic taxidermy, but is rather a compendium full of practical hints and suggestions, recipes, and formulas for the working taxidermist."—The Dial.

Plants. (Plant Relations and Plant Structures in one volume.)

By JOHN M. COULTER, A.M., Ph.D., Head of Department of Botany, University of Chicago, 12mo. Cloth, $1.80 net. (One of the Twentieth Century Text-Books.)

D. APPLETON AND COMPANY, NEW YORK.

EVOLUTION OF MAN AND CHRISTIANITY.

New edition. By the Rev. HOWARD MACQUEARY. With a new Preface, in which the Author answers his Critics, and with some important Additions, 12mo. Cloth, $1.75.

"This is a revised and enlarged edition of a book published last year. The author reviews criticisms upon the first edition, denies that he rejects the doctrine of the incarnation, admits his doubts of the physical resurrection of Christ, and his belief in evolution. The volume is to be marked as one of the most profound expressions of the modern movement toward broader theological positions."—Brooklyn Times.

HISTORY OF THE CONFLICT BETWEEN RELIGION AND SCIENCE. By Dr. JOHN WILLIAM DRAPER. 12mo. Cloth, $1.75.

"The keynote to this volume is found in the antagonism between the progressive tendencies of the human mind and the pretensions of ecclesiastical authority, as developed in the history of modern science. No previous writer has treated the subject from this point of view, and the present monograph will be found to possess no less originality of conception than vigor of reasoning and wealth of erudition."—New York Tribune.

A CRITICAL HISTORY OF FREE THOUGHT IN REFERENCE TO THE CHRISTIAN RELIGION. By Rev. Canon ADAM STOREY FARRAR, D.D., F.R.S., etc. 12mo. Cloth, $1.50.

"A conflict might naturally be anticipated between the reasoning faculties of man and a religion which claims the right, on superhuman authority, to impose limits on the field or manner of their exercise. It is the chief of the movements of free thought which it is my purpose to describe, in their historic succession and their connection with intellectual causes. We must ascertain the facts, discover the causes, and read the moral."—The Author.

CREATION OR EVOLUTION? A Philosophical Inquiry. By GEORGE TICNOR CURTIS. 12mo. Cloth, $2.00.

"A treatise on the great question of Creation or Evolution by one who is neither a naturalist nor theologian, and who does not profess to bring to the discussion a special equipment in either of the sciences which the controversy arrays against each other, may seem strange at first sight; but Mr. Curtis will satisfy the reader, before many pages have been turned, that he has a substantial contribution to make to the debate, and that his book is one to be treated with respect. His part is to apply to the reasonings of the men of science the rigid scrutiny with which the lawyer is accustomed to test the value and pertinency of testimony, and the legitimacy of inferences from established facts."—New York Tribune.

D. APPLETON AND COMPANY, NEW YORK.

THE END