Part 6

—> Skeletal-cells (e) (a) Germ-cell —> Glandular-cells (e) —> Muscle-cells (e) —> Nerve-cells (e) | | | | | | | | II | | | | | | | | —> Skeletal-cells (f) v v v v —> Glandular-cells (f) (b) Germ-cell —> Muscle-cells (f) —> Nerve-cells (f) | | | | | | | | III | | | | —> Skeletal-cells (g) v v v v —> Glandular-cells (g) (c) Germ-cell —> Muscle-cells (g) —> Nerve-cells (g) | | | | | | | | v v v v (d) Germ-cell. ]

Scheme 2. =Illustrating the theory of Continuity of the Germ-Cells; pure germinal inheritance; and the non-transmissibility of acquired characters. The germ-cells are insulated from the body cells.= The germ-cell (a) develops into the body-cells, e, e, e, e, and the germ-cells (b), in animal I. The body-cells, e, e, e, e, do not influence in any way the germ-cells (b), as indicated by the absence of perpendicular arrows. The germ-cells (b) get all their heritages from the antecedent germ-cell (a), as indicated by the oblique arrow from (a) to (b). All heritages are purely through the germ-cells. The same with the animals II and III. Germ-cells (a), (b), (c), (d), are connected together by obliquely placed arrows, indicating the continuity of the germ-cells.

Scheme 3. =Illustrating the theory of Continuity with Modified Pangenesis.= A germ-cell (a) develops into the body-cells, e, e, e, e, and the germ-cells (b) of animal I. The germ-cells (b) get their heritages directly from the germ-cell (a), as indicated by the long, obliquely-situated arrow (continuity of the germ-cells). The germ-cells (b) are, moreover, modified by influences extending from the body-cells, e, e, e, e, as indicated by the perpendicular arrows. A modified germ-cell (b) can develop into a modified animal II, and the body-cells of this animal can influence and modify the germ-cells (c); and so on, indefinitely. The perpendicular arrows indicate that acquired characters are transmitted, and that, too, through the germ-cells.

Professor Morgan, of England, has advanced the ingenious theory, which may reconcile the above-mentioned antagonistic views, that somatic variations, in the direction of adaptation, pave the way for germinal variations, so that, while somatic modifications _as such_ are not inherited, they are yet the _favoring conditions_ under which germinal variations are preserved by the great principle of natural selection. If this is true, as we think it is, then we can safely state that each man in his totality is the resultant of two great factors—_heredity_ and _environment_, the latter including not only food, water, climate, occupation, etc., but also the character of the civilization, the state of morals in society, the ideals and examples most frequently seen, etc., etc.

Heredity brings down to him the streams of tendency of former generations, often of a healthy and beneficent character, but also often surcharged with lust and passion, and reeking with disease.

Environment is the coöperating and, to us, vitally important factor, inasmuch as it may supplement and thus reënforce the hereditary tendencies, whether good or bad; or it may even tend to turn them into new channels, correcting the evil or vitiating the good.

Man is not simply a creature of the present, but profoundly a product of the past. Bodily structure, moral and intellectual tendencies, disease, vices, and virtues are all in the marvelous stream of heritage that comes to him from the past. “Diseases that no facts in the individual life can account for point gaunt fingers of blame from one generation to another. Not a murderer is hung, not a daughter starts on the downward way, but a great company, like those who were present at the stoning of Stephen, stand by inaugurating and consenting to the ruin.”[4]

Truly has it been said that the past is at work in the present, its powers reaching down through the ages, to all the race, largely molding every human life, touching and influencing every individual’s thought and will, and, more than any other force, coloring history.

Studies in heredity illustrate most luridly that the continuity of the human race is a terrible but remorseless reality.

If the ignorance and the perverted pleasures of one generation may produce the vices and the crimes and the diseases of another, a question of tremendous import arises: Is heredity as potent in the direction of virtue and health as of vice and disease? At the first look one is almost tempted to answer Nay! for the most striking examples of heredity seem to be in the direction of evil. But this is perfectly natural. Decay is always more rapid than growth. A cherry rots much more quickly than it ripens. Vice and disease spread much more quickly and widely than virtue and health. But all history and all social and medical science teach that vice and disease carry within themselves the seeds of decay, and virtue and health the seeds of endurance and growth.

Through the great Darwinian principle of natural selection, or survival of the fittest, vice and disease will become less and less predominant, and virtue and hygienic constitutions more and more disseminated.

As influencing a man’s life and character,[5] which is the stronger factor, heredity or environment? Fatalism or choice? In our opinion, as the result of long study and reading, where we have an average man of “_mens sana in corpore sano_,” environment will be the stronger factor whether for good or for evil—that is, in men in general, who have no organic defect, such as insanity or idiocy, and allied affections, the stronger force is environment; but in those having such defect, heredity is the controlling power, and, we may add, the destroying power.

It must be recalled, though, that the average man with a “sound mind in a sound body,” in his development to his present estate, has become possessed of a vast aggregate of diverse heritages, of varying age, strength and dignity. Some of them are so old and strong that they seem to be cast in unyielding molds, while others are so weak and recent that they fluctuate with every passing circumstance. The most dignified and important of all his heritages is that of rational volition. It is the play of this volition upon many of his other heritages that gives him the power of selecting, to a limited extent, his environment.

Every man is born into the world with a certain physical constitution, and, therefore, with a given temperament; with certain passions; with the power of judgment; and with a certain strength of will. If the power of his will be not equal to the strength of his passions, the latter will surely predominate and will display him as the slave of heredity. If he has such an organization of his nervous system that his volition is superior to his passions, he will be none the less the servant of heredity, though a being now possessed of the power of Free-Will.

Man is, to a far greater degree than is ordinarily realized, the servant of heredity. It seems to us an incontrovertible fact that every living creature, at any given moment, is swayed infinitely more by the _totality of its heritages_ than by its environment. No one can possibly deny this so far as plants and most animals are concerned. Nor, if one look below the surface, can it be denied of the higher animals and of man. Happily, the average man, with his present constitution, has his diverse heritages so proportioned that we may repeat that his life and character (in customs, morals, and religion) are vastly more influenced by environment than by heredity.

The standards for estimating the life and character of men, namely, human customs, morals, and religions, are such recent acquisitions, _geologically_ speaking, that they have, as yet, very slightly if at all influenced the germ-cells. They are acquired (somatic) characteristics, and not congenital (germinal) qualities. They are preëminently the creations of environment. If the infants of a Catholic family which is descended from a long line of Catholic ancestors were to be placed and retained in a purely Mohammedan environment, heredity would carry no Christian customs, morals or religion into that environment, but, on the contrary, the Mohammedan surroundings would instill new customs, different ethical ideas, and a different religion. This illustrates how very feebly indeed are germ-cells correspondingly impressed by pure acquired characters. _It is almost certain that the translation of somatic changes into germinal changes is appallingly slow._ As far, then, as social customs, morals, and religion are concerned, the average man is, in our opinion, infinitely more the creature of nurture than of nature. But, as far as his temperament, his emotional nature, his judgment, his strength of will, in short, his physical and therefore his mental constitution, are concerned, he is _almost_ absolutely the creature of heredity. The equilibrium of qualities or heritages in the average man, resident in a given, stable community, is in harmony with the average customs, ethical ideas, and religious beliefs of that community. But in all stable communities there are men whose resultant of heritages, some in one direction and some in another, places them out of harmony with the average of their social environment, and they are looked upon, some as idiots, some as geniuses, some as criminals, and others as saints, and so on. So that again we may say that a man’s character in a community is the resultant of an hereditary physical constitution, and his environment. Some men may inherit such a physical constitution that in spite of the best environment they are much debased below the average man; others may possess such heritages that, notwithstanding adverse circumstances, they reach a level of character much above the average man. And there are all gradations between the two extremes.

SECTION III.

UNSTABLE ENVIRONMENT.

UNSTABLE ENVIRONMENT.

Where living creatures are in harmony with their surroundings,—where, in other words, they are adapted to their environment,—and where, further, this environment is apparently in a state of equilibrium; there we find the fewest and least marked variations in the living creatures. To the casual observer the face of nature maintains the same guise from year to year. The earth seems solid and unyielding; the mountains appear to be everlasting; the restless waters of rivers and brooks seemingly move and throb in the same channel; the tides ebb and flow in apparently unchanging ocean beds; the birds and flowers and woodlands look alike from year to year; and all the varied phenomena of nature appear completed and permanent, as if the present world were constructed in an unyielding mold.

But nothing is fixed and rigid in nature. The earth itself travels rapidly through space and brings in due season spring, summer, autumn and winter; revolves upon its axis and alternates the starry night with sunshine; and periodically changes its orbit so that at one time the northern pole has a temperate climate where water lilies may grow, and at another period presents an arctic climate with impassable barriers of ice. Ice and frost and other forces are breaking up the rocks of mountains, making larger and smaller fragments and even powder; the rains descend and the mountain brooks are swollen to resistless torrents which carry the fragments and mud to the rivers, and these latter take the mud on to the ocean.

Thus, by degrees, the mountains, hills and all the earth are being eroded and the great bulk of the detritus carried by the rivers to the sea and deposited along the sea margins. Thus sedimentation goes along with erosion, and gradually marginal sea bottoms of immense thickness are formed, which will in time be consolidated into rocks and uplifted as dry land. The ceaseless grinding of waves and tides erodes the coast line and adds _débris_ to the marginal sea bottom. The finest sediment is carried out by the tides so far as to reach the ocean currents, and thus is strewn broadcast over portions of deep-sea bottom, and will also in due time be consolidated into rock.

Myriads of animals that form calcareous shells live and die in the ocean. The shells of the dead animals are falling like a perpetual shower on certain ocean bottoms, year after year, so that immense accumulations of calcareous substances occur there, which will also in time be consolidated into limestone rocks, and uplifted as dry land.

Deltas are forming at present at the mouths of certain rivers, and estuaries at others. Lands are now gradually emerging from the sea in some places and at others sinking into the sea. The entire coast of Scandinavia, both on the Baltic and Atlantic sides, is rising out of the sea, and has been doing so for a long time. It is rising at the rate of more than two feet in a hundred years. During an immense period of time there has been a gradual elevation of all the southern part of the South American continent. Sometimes a large elevation takes place rapidly. In 1822, and again in 1835, the southwest coast of South America, after severe earthquakes, was elevated several feet along a distance of several hundred miles. It is known that the coast of Greenland, for five hundred miles, is subsiding. From a study of coral barriers and atolls it is believed that an area of the mid-Pacific sea bottom covering over ten million square miles is sinking and has been doing so for a long time.

The foregoing facts tend to illustrate the truth that nothing is permanent in the environment of living creatures at present. All surroundings are perpetually changing, though apparently ever so slowly. The changes that are now going on were also taking place yesterday, last week, last century, last æon, and so on throughout geologic time. Gradual oscillations of the earth’s crust on a grand scale and affecting whole continents, but usually so slowly as to escape popular observation, have been taking place ceaselessly through inconceivable ages. These oscillations have produced all the great inequalities of the earth’s surface, such as ocean basins, continents and mountain chains. The oscillations are probably due to the slow cooling and unequal shrinking of the whole earth which has been progressive through all geologic time.

The state of the contest between the eroding and the uplifting agencies of the world at any time determines the height of mountains and continents, the depths of seas, the distribution of land and water, for that period.

Knowing that the present physical agencies at work on the globe have been acting through long ages,[6] it can readily be appreciated how small effects have been accumulated and low elevations, for instance, have become immense, high mountain ranges. The growing mountain ranges alter the climate and the meteorological conditions. The rainfall on one side differs from that on the other. The temperature varies with the altitude, and so on.

Although continents have gradually and steadily grown from the earliest times, there have been many local alterations of land and sea. Marginal sea bottoms have become great mountain ranges. Islands have appeared and sunk from view. Lakes have been gradually converted into solid land or into peat bogs. Fresh water bodies have become brackish. Dry lands have become marshes, and forests have been buried beneath the waves. Geologic changes have caused great alterations in climate at given times and in given areas.

These statements may be illustrated and emphasized by a brief reference to the =development of the Continent of North America=. This Continent has grown from comparatively a small beginning to its present great proportions. In doing so it has passed through eras of stupendous duration. These eras in the order of their occurrence are as follows:

(1) =Archæan era=; (2) =Palæozoic era= (subdivided into =Cambrian=, =Silurian=, =Devonian= and =Carboniferous= periods); (3) =Mesozoic era= (subdivided into =Triassic=, =Jurassic= and =Cretaceous= periods); (4) =Cenozoic era= (subdivided into =Tertiary= and =Quaternary= periods); the Tertiary is subdivided into =Eocene=, =Miocene= and =Pliocene= epochs; the Quaternary is subdivided into =Glacial=, =Champlain= and =Terrace= epochs; (5) =Psychozoic era=, or recent epoch.

The physical geography of the continent at the close of that early geologic era known as the =Archæan= is shown on the map (Fig. 11). At this time the vast portion of the continent, whose outlines nevertheless existed, was submerged under a shallow sea, as indicated by the dark shading on the figure. The white V-shaped mass, starting just above the site of the great lakes and extending on the one hand in a northeasterly direction to Labrador, and on the other in a northwesterly direction to the Arctic Ocean, is the emerged land of this _Archæan_ time. Smaller masses of Archæan land are also seen at the site of the Blue Ridge Mountains in the east and at that of the Rocky Mountains in the west. Around these lands as a nucleus the North American Continent has been built. Therefore, at the close of the Archæan or beginning of the next, or =Palæozoic era=, the whole interior portion of the continent was covered by a shallow sea which beat against the Canadian Archæan land on the north, the Blue Ridge Archæan land on the east, and the Rocky Mountain Archæan land on the west. This shallow sea is known as the _Palæozoic Sea_. Throughout the vast ages of the Palæozoic era, immense sediments were being deposited along the marginal sea bottoms. The deposition of these sediments was simultaneous with a further sinking of the submerged continent, so that the shallowness of the Palæozoic Sea was maintained; finally, the uplifting forces predominated, and the submerged land along the margins of the Canadian Archæan appeared as dry land, and thus increased the area of the infant continent. During all this period there was a steady and slow growth of the land southward from the Canadian Archæan, so that towards its close the visible continent had increased nearly, though not exactly, to the proportions attained in a still later (=Cretaceous=) period (Fig. 12).

At the close of the Palæozoic era the slow, steady changes that had been going on were replaced by more rapid and comparatively revolutionary changes, which caused great alterations in the physical geography and climate. Hitherto the continent had been comparatively low. Now the vast sedimentary accumulations constituting the marginal sea bottom of the eastern portion of the Palæozoic Sea, which had been accumulating through all Palæozoic time, were uplifted into the great Appalachian chain of mountains.