The Fitness of the Environment

The original of tliis book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. Darwinian fitness is compounded of a mutual relationship between the organism and the environment. Of this, fitness of en- vironment is quite as essential a component as the fitness which arises in the process of or- ganic evolution ; and in fundamental charac- teristics the actual environment is the fittest possible abode of life. Such is the thesis which the present volume seeks to establish. This is not a novel hypothesis. In rudimen- tary form it has already a long history behind it, and it was a familiar doctrine in the early nineteenth century. It presents itself anew as a result of the recent growth of the science of physical chemistry.

About fifteen years ago I first beca^me inter- ested in the connection between physical and chemical properties of simple substances and the organic functions which they serve. At that time the applications of the new physical chemistry to physiology were only just begin- ning, and the older speculations of natural theology upon such subjects had long since passed into oblivion. It was a time of very little interest in such matters, for many lines of development of natural science during the preceding quarter century had conspired to divert attention to other problems. The im- mediate occasion of my interest was, I well remember, the chance reading of Maly's im- portant but almost forgotten papers upon the diffusion and dialysis of phosphates, re- counting phenomena which, in the light of the modern theory of ionization, appeared simple enough, though to their discoverer they had been in some respects inexplicable. A series of researches have grown out of this interest, and since that time, whenever freedom has permitted, I have been occupied with various aspects of the problem of the neutrality or faint alkalinity of the organism. For it soon appeared that the key to the peculiar condi- tions of equilibrium between acids and bases in blood and protoplasm is to be found in such characteristics of phosphate solutions as Maly had observed, and in like behavior of similar solutions containing carbonic acid. When at length it became possible quantitatively to describe the chemical equilibra in such sys- tems, it was at once clear that, of all known substances, phosphoric acid and carbonic acid possess the greatest power of automatic regu-

lation of neutrality (the concentration of ion- ized hydrogen and hydroxy! at the neutral point) . One does not like to accept a fact of such far-reaching importance as mere chance, and yet no other explanation was at hand. For, after the briefest consideration, it was obvious that here, at least, natural selection could not be involved. But it was also certain that this is no unique instance of a property of a simple substance automatically serving a very useful purpose in the processes of life. Like every one who has received a chemical training, I was vaguely conscious of numerous other simi- lar cases ; like every one who has any acquaint- ance with the general properties of matter, I knew that the remarkable thermal properties of water are of great importance to living or- ganisms. However, in spite of the fact that I had been brought face to face with a definite problem whose solution now appears to be perfectly* patent, so great is the natural inertia of the mind, and so firmly established was the belief that natural selection is, on the whole, quite adequate to account for biological fit- ness, that for a number of years I made no further progress.

Then, finally, after a long period of uncer- tainty, came the realization of the reciprocal character of Darwinian fitness, and at once the whole difficulty was resolved. On all sides instances of environmental fitness were manifest, and casual search brought many other cases to hght. The forgotten literature of natural theology is crammed with illustra- tions, and the recent biological developments of physical chemistry have provided still others. It is, indeed, a very curious episode in the history of thought that these well- known facts should have been so long forgot- ten or misconstrued. But, though forgotten, they have, so to speak, lain dormant in the minds of physical scientists, and I have found both chemists and physicists ready to accept them without hesitation. In the following pages an attempt has been made to collect and to interpret such facts, in so far as they arise among the compounds of carbon, hydro- gen, and oxygen, especially in the cases of water and carbonic acid. This restriction has been adopted in order to facilitate the logical discussion, and it should be borne in mind that other phenomena, dependent upon the properties of other substances, such as the above-mentioned characteristics of phosphate solutions, belong in the same category.

The argument which has been thus devel- oped is comparatively rigid and closely woven. That is, perhaps, in some respects unfortunate, because the impression which must be pro- duced is unlike that of the facts themselves, and the argument is certainly very different from the mental process through which I have myself passed in reaching the conclusion. But it would be very difficult indeed in any other manner to set forth all the necessary consid- erations, so that they should be intelligible to any one but the physico-chemical biologist, and on the whole there seems to be no choice but to follow a logical rather than a descrip- tive method. The reader will find, however, that in the main Chapters III, IV, V, and VI are concerned with evidence alone. This taken together, as a whole, is the only true ground for a conclusion, and it is upon the general character of the evidence rather than upon an argument which only serves as a means to the end that I should wish to rest my case. To many, on the other hand, as to any biologist who may not care to examine the difficult facts of physics and chemistry, Chapters I, II, VII, and VIII will be sufficient to explain both the purpose of the book and the outcome of the investigation.

There has been a constant effort to restrict all discussions to the utmost, because at the pres- ent time encyclopaedic handbooks covering all departments of science have so multiplied that hardly any facts or theories which come within the scope of this work are inaccessible to the general reader. On the other hand, it has been deemed necessary to explain every sub- ject as it has arisen, for many of the readers of this volume will perhaps be unfamiliar even with the rudiments of all the departments of science which have necessarily been touched upon.

Much of the content of the following pages has already been set forth in lectures. The general conclusion was presented last February to the members of the Harvard Seminary of Logic ; later in the academic year I delivered the substance of the book as part of a college course to my students of biological chemistry in Harvard College. I am indebted to many of my colleagues in Harvard for valuable assistance, criticism, and expressions of opinion. Without such assurances that I have not fallen into gross blunders, and that the conclusions appear rea- sonable to experienced men of science, I should not have dared to undertake a task which overtaxes my knowledge, or positively to as- sert a proposition which is in conflict with much of the scientific thought of the last half century. Especial thanks are due to Professor

Josiah Royce. His learning and generosity have in the past aided me to reach an under- standing of the philosophical problems of sci- ence, and in the preparation of this book they have repeatedly guided me aright. V. Gbnebai Cosmogbaphical Conclusions . . 60 VI. The Pbimabt Constituents op the Envibon- D. Expansion before Freezing .... 106 n. The Action op Water upon Other Substances 110 IDEAS of purpose and order are among the first concepts regarding their en- vironment which appear, as vague antici- pations of philosophy and science, in the minds of men. In truth, when the manifold phenomena and experiences of daily life stored in the memory are critically scruti- nized, purpose and order seem naturally to suggest themselves as explanations of the universe. Day and night, the changing but recurring seasons, the fertilizing sunshine and rain, the flight of birds, the powers of the human hand, and all the beauties and mysteries of nature cannot fail of such in- terpretation by the simple and untrained mind. Alike anthropology and the history of primitive civilizations bear witness to this natural tendency of thought. Such ideas pre-

cede exact knowledge and civilization, and arise spontaneously among savage peoples. They are the solvent of the chaos, as which the outer world first presents itself to our eyes and hands, and they are the fabric of all theologies. As civilization has progressed, these early hypotheses have received endless criticism, and their definition has been continually sharpened. Meantime natural science has sought and provided ever more accurate accounts of the phenomena which first sug- gested them to man, and of countless other forms and transformations of matter and energy, and the discovery of laws of nature has steadily changed once quite mysterious order and 'purpose into the plainest of neces- sary results.

Upon the advent of modern science Order speedily began to receive its true account when, after only a half century of progress, dynamics through Newton provided a formu- lation of the laws which govern the most striking of all the orderly phenomena of nature.^ Since Newton's day the explana- ' " Die Newton'schen Principien sind geniigend, um ohne Hinzuziehung eines neuen Princips jeden praktisch vorkom- menden mechanischen Fall, ob derselbe nun der Statik oder der Dynamik angehort, zu durchschauen. Wenn sich hierbei Schwierigkeiten ergeben, so sind dieselben immer nur mathe-

tion of natural order as the automatic result of natural law has not ceased, and at length has become so nearly complete that the ap- pearance of order under any circumstances is now taken as proof of the existence of a law, "* The fate of the hypothesis of purpose in nature has been less simple, because the dis- covery of law, or even of the possibility of law, underlying adaptation and fitness was more difficult. Until the middle of the nine- teenth century the countless adaptations of organisms to the environment and the mani- fest fitness of nature for the activities of living things seemed to many biologists only explicable as the result of some directing force.^ Even skeptics were nearly or quite

mathischer (formeller) und keineswegs mehr principieller Natur." — Mach, "Die Mechanik in Ihrer Entwickelung Historisch-Kritisch Dargestellt." Leipzig, 1897, 3d ed., p. 257. "Dann hat er auch die Aufstellung der heute angenom- men Principien der Mechanik zu einem Abschluss gebracht." — Mach, ibid. p. 181. * See for example that remarkable series of works, the Bridgewater Treatises "On the Power, Wisdom, and Goodness of God, as manifested in the Creation ; illustrating such work by all reasonable arguments, as for instance the variety and formation of God's creatures in the animal, vegetable, and mineral kingdoms; the efifect of digestion, and thereby of conversion; the construction of the hand of man, and an infinite variety of other arguments ; as also by discoveries ancient and modern, in arts, sciences, and the whole extent of literature." — Whewell, "Astronomy and General Phys-

unable, however strong their desire, to ac- count for the facts with a plausible theory. The dogma of final .causes had led a thou- sand times to the truth by teaching the investigator that the true description of an organ or physiological process was to be found in its utility to the organism as a whole. Such considerations were far too numerous and too patent for science to shirk some explanation, and the only weighty explana- tion at hand seemed the teleological one.

With a suddenness which to many seemed catastrophic Darwin's hypothesis of natural selection changed the whole aspect of the problem. Law appeared as the basis of purpose just as it had appeared as the basis of order, and adaptations became, in the judg- ment of most men, the necessary results of* an automatic process. To-day, after a half century, there is no longer room for doubt that the fitness of organic beings for their life in the world has been won in whole or in part

ics Considered with Reference to Natural Theology." Lon- don, 1834, 4th ed., p. ix. To this series such men as Whewelland Sir Charles Bell contributed. by an almost infinite series of adaptations of life to its environment, whereby, througb a corresponding series of .transformations, pres- ent complexity has grown out of former sim- plicity.^ The great and fruitful ideas which Darwin brought to the attention of the whole world have long since been incorporated into hu- man thought. Not the least important among them is the new scientific concept of fitness, as it emerges from the discussion of natural selection. Before Darwin, this concept possessed all the vagueness of an idea which, though in part founded on observation, was not to be explained with the help of existing scientific theories. But although Darwin's fitness involves that which fits and that which is fitted, or more correctly a reciprocal rela- tionship, it has been the habit of biologists since Darwin to consider only the adaptations of the living organism to the environment.^

* The ideas which are associated with the names of de Vries, as well as the very dififerent hypotheses of Driesch, Bergson, and others are, of course, concerned with the manner, not with the fact of adaptation and organic evolution. ' Far different was the earlier point of view. An examina- tion of Whewell's Bridgewater Treatise at once reveals im- portant, if often fallacious, discussions of environmental fit- ness; e.g. "It has been shown in the preceding chapters that a great number of quantities and laws appear to have been selected in the construction of the universe ; and that by the

For them, in fact, the environment, in its past, present, and future, has been an inde- pendent variable, and it has not entered into any of the modern speculations to consider if by chance the material universe also may be subjected to laws which are in the largest sense important in organic evolution. Yet fitness there must be, in environment as well as in the organism. How, for example, could man adapt his civilization to water power if no water power existed within his reach ?

adjustment to each other of the magnitudes and laws thus selected, the constitution of the world is what we find it, and is fitted for the support of vegetables and animals in a manner in which it could not have been, if the properties and quan- tities of the elements had been different from what they are. We shall here recapitulate the principal of the laws and magnitudes to which this conclusion has been shown to apply. 1. The Length of the Year, which depends on the force of the attraction of the sun, and its distance from the earth.

3. The Mass of the Earth, which depends on its magni- tude and density. 9. The Law and Rate of the Expansion of Water by Cold, below 40 degrees. At first sight it may well seem that inquiry into such a problem must end unsuccessfully in vague and unprofitable guesses. Indeed the past has brought forth no lack of such vain attempts, usually guided by a devotion to the doctrine of design in the service of the- ology. Yet other sciences have grown since 1859, and physical and chemical data in abundance are now at hand to aid in a recon- sideration of the environment's fitness, if

10. The Law and Quantity of tlie Expansion of Water by Freezing. 15. The Quantity of Heat absorbed in the Expansion of Air by Heat. 16. The Law and Rate of the Passage of Aqueous Vapor through Air. 17. The Laws of Electricity; its relations to Air and Moisture. 18. The Fluidity, Density, and Elasticity of the Air, by means of which its vibrations produce Sound. "' 19. The Fluidity, Density, and Elasticity of the Ether, by means of which its vibrations produce Light." — Whe- WBLL, "Astronomy and General ' Physics Considered with Reference to Natural Theology." London, 1834, 4th ed., pp. 141-143.

It is hard to understand how such ideas could have fallen into oblivion. such exist. Clearly it is well to seek among these data for a more precise formulation of the problem, which may then perchance lead to some more ambitious quest, or at least to new understanding of the old failure. The world of our senses is a world of matter and energy, space and time. After centuries of philosophical and scientific study, these, the very logical elements of science, are no doubt still without a final description. None the less is there sound foundation for the belief that our preliminary accounts of all four possess completeness in some respects and for certain purposes. Nor are we to-day less confident of the finality of some of our ideas regarding the nature of life and the vital processes, as they exist in this world. But both of these conclusions call for further consideration.

Many facts contribute to the belief, uni- versal among chemists, that the known ele- ments constitute by far the greatest part of a system of materials out of which the uni- verse is formed, within which all chemical changes (except certain phenomena of radium and a few other anomalies, including perhaps unknown changes in the interiors of the celestial bodies) take place. It is certain that nearly all the chemical transformations upon the earth consist of rearrangements of the atoms of the known elements. A century and a half of scientific chemistry guarantee that conclusion with a security rarely attained in descriptive science. And the testimony of the spectroscope is equally conclusive that the visible stars, like the sun itself, are made up almost or quite exclusively of the same chemical ele- ments. Such facts, so familiar that they re- quire no comment or explanation, might sufficiently justify the acceptance of the chem- ist's known elements as the only important matter in the universe. But even more weighty evidence is at hand; I mean the so-called periodic classification of the ele- ments.

It has long been evident that simple rela- tionships exist in some cases between the atomic weights of similar elements. For ex- ample, the atomic weights of bromine, stron- tium, and selenium are approximately equal to the means of the atomic weights of chlorine and iodine, of calcium and barium, and of sulphur and tellurium respectively. More general relationships between the atomic weights and properties of the elements were first pointed out by Newlands in 1864 and were extended by Mendeleeff and Lothar Meyer a little later. Out of these studies has arisen the law that the properties of the elements are periodic functions of their atomic weights.

The essential characteristics of tliis law are best illustrated by a consideration of the relative volumes occupied by atoms of the various elementary substances, the so-called atomic volumes, which may be expressed by dividing atomic weights by specific gravities. The facts are graphically represented upon the accompanying diagram, where atomic weights are plotted horizontally, atomic vol- umes vertically. Beginning with lithium the volumes fall to boron and carbon, then rise irregularly to sodium. A second fall leads to aluminium, a second rise to potassium, and then the rises and falls of the curve are repeated until, among the elements of higher atomic weight, gaps break the continuity of the relationship. On the whole curve similar elements occupy

similar positions. Thus the alkali metals, lithium, sodium, potassium, rubidium, and caesium, occupy the crests of the waves; the halogens, fluorine, chlorine, bromine, and iodine, fall about midway between crests and troughs, and a little further study dis- closes a host of other corresponding relation- ships. Similar periodic variations may be shown to occur in other physical properties of the elements ; — the melting points, the boiling points, the magnetic characteristics, etc. Even more striking are the periodic varia- tions in chemical properties, including the general characteristics which first led to the idea of rational classification, and more spe- cific qualities like the combining powers for hydrogen, oxygen, and other elements.

The clearest proof of the value of the periodic classification has been the predic- tion of "new" elements, and accurate fore- knowledge of their properties. Thus when Mendeleeff first described the system, the element germanium, discovered by Winkler in 1886, was unknown ; but from the proper- ties of the elements surrounding a gap in the system the Russian chemist was able to predict its properties with almost incredible exactness, as the following table shows.

Atomic weight . . . Specific gravity . . . Atomic volume . . . Formula of oxide . . Specific gravity of oxide Formula of chloride . Boiling point of chloride Specific gravity of chloride Formula of fluoride . . Formula of ethyl compound Specific gravity of ethyl compound Finally it is to be especially noted that, upon arranging the known elements in a table rationally constructed upon the basis of the above recorded facts, comparatively few spaces within the range of known atomic weights remain to be filled. The conclusion is obvious that very few elements now un- known are possible unless they possess very high atomic weights. But the apparent transmutation of radium into helium is a pretty clear indication that elements of very high atomic weight may be unstable. If they have existed in number and large quan- tity, they probably have long since ceased so to exist, except perhaps in the interior of celestial bodies, and they are not likely elsewhere to complicate natural phenomena by their unknown properties.

The behavior of radium and the classifica- tion jtself suggest one further idea: the hy- pothesis that the elements are genetically related, that they have been evolved by some unknown process according to unknown laws. Certain it is that the properties of matter are no chance phenomena, and that transmuta- tion has ceased to be merely a philosopher's dream. All of these familiar facts of chemical science fully justify us in dealing, with matter as a known factor in the study of life conditions in the universe. For, whatever may be the fate of present theories, our present practical knowledge of the behavior of matter cannot fail us in the future.

Contemporary with the work of Darwin and of Mendeleeff were the feats of Mayer, Joule, Helmholtz, Kelvin, and Clausius, whereby ideas of energy assumed their mod- ern aspect. In the revolution wrought by these men imponderables and fluids vanished from this domain, and energy became that which, not being matter, is conserved. The new principles of the 'fifties have held their own until to-day. Meantime they have made of thermodynamics (the department of science which is especially concerned with the laws of energy transformation) a sub- ject which few who cultivate the physical sciences may disregard. Countless develop- ments and achievements of thermodynamics give very real ground for the belief that we may speculate about the transformations of energy in the universe with the same assur- ance that we have in discussing chemical changes.

Our reasons for confidence in the truth of current general notions of energy, and in their adequacy to account for any phenomena so far as energy is concerned, wherever life exists in the universe, are manifold, and not unlike those which have been reviewed in dis- cussing the elements. Centuries of search have revealed, in addi- tion to that most obvious form which is studied in dynamics, a very small number of varieties or manifestations of energy, such as heat, electricity, magnetism, optical energy, and chemical energy. Such manifestations of energy are by no means confined to the earth or to the solar system. Indeed Newton first worked out the general laws of dynamics and erected them into a complete science with the aid, not of terrestrial, but of astro-