CHAPTER X_The Whence and the Whither of Man A Brief History of His Origin and Development through Conformity to Environment; Being the Morse Lectures of 1895

PRESENT ASPECTS OF THE THEORY OF EVOLUTION

In all our study we have taken for granted the truth of the theory

of evolution. If you are not already persuaded of this by the

writings of Darwin, Wallace, and many others, no words or arguments

of mine would convince you. We have used as the foundation of our

argument only the fundamental propositions of Mr. Darwin's theory.

But while all evolutionists accept these propositions they differ

more or less in the weight or efficiency which they assign to each.

In a sum in multiplication you may gain the same product by using

different factors; but if the product is to be constant, if you

halve one factor, you must double another. Evolution is a product of

many factors. One evolutionist lays more, another less, emphasis on

natural selection, according as he assigns less or more efficiency

to other forces or processes. Furthermore, evolutionists differ

widely in questions of detail, and some of these subsidiary

questions are of great practical importance and interest. It may be

useful, therefore, to review these propositions in the light of the

facts which we have gathered, and to see how they are interpreted,

and what emphasis is laid on each by different thinkers.

The fundamental fact on which Mr. Darwin's theory rests is the

"struggle for existence." Life is not something to be idly enjoyed,

but a prize to be won; the world is not a play-ground, but an arena.

And the severity of the struggle can scarcely be overrated. Only one

or two of a host of runners reach the goal, the others die along the

course. Concerning this there can be no doubt, and there is little

room for difference of interpretation.

The struggle may take the form of a literal battle between two

individuals, or of the individual with inclemency of climate or

other destructive agents. More usually it is a competition, no more

noticeable and no less real than that between merchants or

manufacturers in the same line of trade.

The weeds in our gardens compete with the flowers for food, light,

and place, and crowd them out unless prevented by man. And when the

weeds alone remain, they crowd on each other until only a few of the

hardiest and most vigorous survive. And flowers, by their nectar,

color, and odor, compete for the visits of insects, which insure

cross-fertilization. And fruits are frequently or usually the

inducements by which plants compete for the aid of animals in the

dissemination of their seeds. So there is everywhere competition and

struggle; many fail and perish, few succeed and survive.

In a foot-race it is often very difficult to name the winner. Muscle

alone does not win, not even good heart and lungs. Good judgment,

patience, coolness, courage, many mental and moral qualities, are

essential to the successful athlete. So in the struggle for life.

The race is not always to the swift, nor the battle to the strong.

The total of "points" which wins this "grand prize" is the

aggregate of many items, some of which appear to us very

insignificant. Hence, when we ask, "Who will survive?" the answer is

necessarily vague. Mr. Darwin's answer is, Those best conformed to

their environment; and Mr. Spencer's statement of the survival of

the fittest means the same thing.

The judges who pronounce and execute the verdict of death, or award

the prize of life, are the forces and conditions of environment. We

have already considered the meaning of this word. Many of its forces

and conditions are still unknown, or but very imperfectly

understood. But known or unknown, visible or invisible, the result

of their united action is the extinction or degradation of these

individuals which deviate from certain fairly well-marked lines of

development. We must keep clearly before our minds the fact that the

world of living beings makes up by far the most important part of

the environment of any individual plant or animal. Two plants may be

equally well suited to the soil and climate of any region; but if

one have a scanty development of root or leaf, or is for any reason

more liable to attacks from insects or germs, other things being

equal, it will in time be crowded out by its competitor. Worms are

eaten by lower vertebrates, and these by higher. An animal's

environment, like that of a merchant or manufacturer, is very

largely a matter of the ability and methods of its competitors. And

man, compelled to live in society, makes that part of the

environment by which he is most largely moulded.

This process of extinction Mr. Darwin has called "natural

selection." Natural selection is not a force, but a process,

resulting from the combined action of the forces of environment. It

is not a cause in any proper sense of the word, but a result of a

myriad of interacting forces. The combination of these forces in a

process of natural selection leading directly to a moral and

spiritual goal demands an explanation in some ultimate cause. This

explanation we have already tried to find.

It is a process of extinction. It favors the fittest, but only by

leaving them to enjoy the food and place formerly claimed, or still

furnished, by the less fit. In any advancing group, as the less fit

are crowded out, and the better fitted gain more place and food and

more rapid increase, the whole species becomes on an average better

conformed. More abundant nourishment and increased vigor seem also

to be accompanied by increased variation. And by the extinction of

the less fit the probability is increased that more fit individuals

will pair with one another and give rise to even fitter offspring,

possessing perhaps new and still more valuable variations.

But if, of a group of weaker forms, those alone survive which adopt

a parasitic life, those which in adult life move the least will

survive and reproduce; there will result the survival of the least

muscular and nervous. This degeneration will continue until the

species has sunken into equilibrium, so to speak, with its

surroundings. Here natural selection works for degeneration. Sessile

animals have had a similar history. But these parasitic and sessile

forms had already been hopelessly distanced in the race for life.

Their presence cannot impede the leaders; indeed their survival is

necessary to directly or indirectly furnish food for the better

conformed. In the animal and plant world there is abundant room and

advantage at the top.

Once more, natural selection works as a rule for the survival of

individuals, only indirectly for that of organs composing, or of

species including, these individuals. It may work for the

development of a trait or structure which, while of no immediate

advantage to the individual, increases the probability of its

rearing a larger number of fitter offspring. Thus defence of the

young by birds may be a disadvantage to the parent, but this is more

than counterbalanced in the life of the species by the number of

young coming to maturity and inheriting the trait. Even here natural

selection favors the survival of the trait indirectly by sparing the

descendants of the individual possessing it. Natural selection may

always work on and through individuals without always working for

their sole and selfish advantage.

In human society we find the selection of families, societies,

nations, and civilizations going on, but mainly as the result of the

survival of the fittest individuals.

There may very probably be a struggle for existence between organs

or cells in the body of each individual. The amount of nutriment in

the body is a more or less fixed quantity; and if one organ seizes

more than its fair share, others may or must diminish for lack. But

the limit to this usurpation must apparently be set by the crowding

out of those individuals in which it is carried too far. Natural

selection, so to speak, leaves the individual responsible for the

distribution of the nutriment among the organs, and spares or

destroys the individual as this usurpation proves for its advantage

or disadvantage.

It makes its verdict much as the judges at a great poultry or dog

show count the series of points, giving each one of them a certain

value on a certain scale, and then award the prize to the individual

having the highest aggregate on the whole series. Any such

illustration is very liable to mislead; I wish to emphasize that

fitness to survive is determined by the aggregate of the qualities

of an individual.

But an animal having one organ of great value or capacity may thus

carry off the prize, even though its other organs deserve a much

lower mark. This is the case with man. In almost every respect,

except in brain and hand, he is surpassed by the carnivora, the cat,

for example. But muscle may be marked, in making up the aggregate,

on a scale of 500, and brain on a scale of 5,000, or perhaps of

50,000. A very slight difference in brain capacity outweighs a great

superiority in muscle in the struggle between man and the carnivora,

or between man and man.

The scale on which an organ is marked will be proportional to its

usefulness under the conditions given at a given time. During the

period of development of worms and lower vertebrates much muscle

with a little brain was more useful than more brain with less

muscle. Hence, as a rule, the more muscular survived; the brain

increasing slowly, at first apparently largely because of its

correlation with muscle and sense-organs. At a later date muscle,

tooth, and claw were more useful on the ground; brain and hand in

the trees. Hence carnivora ruled the ground, and certain arboreal

apes became continually more anthropoid. At a later date brain

became more useful even on the ground, and was marked on a higher

scale, because it could invent traps and weapons against which

muscle was of little avail. Just at present brain is of use to, and

valued by, a large portion of society in proportion to its

efficiency in making and selfishly spending money. But slowly and

surely it is becoming of use as an organ of thought, for the sake of

the truth which it can discover and incarnate.

Natural selection works thus apparently for the survival of the

individuals possessing in the aggregate the most complete conformity

to environment. Let us now imagine that an animal is so constructed

as to be capable of variation along several disadvantageous or

neutral lines, and along only one which is advantageous. The

development would of course proceed along the advantageous line. Let

us farther imagine that to the descendants of this individual two,

and only two, advantageous lines of variations are allowed by its

structure. Then natural selection would probably favor the decidedly

advantageous line, if such there were. But as long as the structure

of the animal allows variation along only a few lines, the

two advantageous variations would, according to the law of

probabilities, frequently occur in the same individual. The eggs and

spermatozoa of two such individuals might not infrequently unite,

and thus in time the two characteristics be inherited by a large

fraction of the species.

And now let me quote from Mr. Spencer:

"But in proportion as the life grows complex--in proportion as a

healthy existence cannot be secured by a large endowment of some

one power, but demands many powers; in the same proportion do

there arise obstacles to the increase of any particular power, by

'the preservation of favored races in the struggle for life.' As

fast as the faculties are multiplied, so fast does it become

possible for the several members of a species to have various

kinds of superiorities over one another. While one saves its life

by higher speed, another does the like by clearer vision, another

by keener scent, another by quicker hearing, another by greater

strength, another by unusual power of enduring cold or hunger,

another by special sagacity, another by special timidity, another

by special courage; and others by other bodily and mental

attributes. Now it is unquestionably true that, other things

equal, each of these attributes, giving its possessor an extra

chance of life, is likely to be transmitted to posterity. But

there seems no reason to suppose that it will be increased in

subsequent generations by natural selection. That it may be thus

increased, the individuals not possessing more than average

endowments of it must be more frequently killed off than

individuals highly endowed with it; and this can happen only when

the attribute is one of greater importance, for the time being,

than most of the other attributes. If those members of the

species which have but ordinary shares of it, nevertheless

survive by virtue of other superiorities which they severally

possess, then it is not easy to see how this particular attribute

can be developed by natural selection in subsequent generations.

The probability seems rather to be that, by gamogenesis, this

extra endowment will, on the average, be diminished in

posterity--just serving in the long run to compensate the

deficient endowments of other individuals whose special powers

lie in other directions, and so to keep up the normal structure

of the species. The working out of the process is here somewhat

difficult to follow; but it appears to me that as fast as the

number of bodily and mental faculties increases, and as fast as

the maintenance of life comes to depend less on the amount of any

one, and more on the combined action of all, so fast does the

production of specialties of character by natural selection alone

become difficult. Particularly does this seem to be so with a

species so multitudinous in its powers as mankind, and above all

does it seem to be so with such of the human powers as have but

minor shares in aiding the struggle for life--the æsthetic

faculties for example."--Spencer, "Principles of Biology," § 166.

Can thus natural selection, acting upon fortuitous variations, be

the sole guiding process concerned in progress? Must there not be

some combining power to produce the higher individuals which are

prerequisites to the working of natural selection?

We are considering the efficiency of natural selection in enhancing

useful variations through a series of generations. Let us return to

the distinction between productiveness and prospectiveness of social

capital. Applied to variations productiveness means immediate

advantage, prospectiveness the greater future and permanent returns.

Now all persisting variations must, in animals below man, apparently

be somewhat productive, else they would not continue, much less

increase. Now the immediate return from prospective variations is

often smaller than from productive. It looks at first as if

productive variations would always be preserved by natural

selection, and that prospective variations would not long advance.

Yet in the muscular system variations valuable largely for their

future value are neither few nor unimportant. How can the brain in

its infancy develop until it gains supremacy over muscle, or muscle

have done the same with digestion? Now a partial explanation of this

is to be found in the correlation of organs. This is therefore a

factor of vast importance in progress through evolution.

Progress in any one line demands correlated changes in many organs.

Thus in the advance of annelids to insects the muscular system

increases in relative bulk, and absolutely in complexity. But a

change or increase in the muscle must be accompanied by

corresponding changes in the motor-nerve fibrils; and these again

would be useless unless accompanied by increased complexity and more

or less readjustment of the cells and fibrils of the nerve-centres.

And all these additions to, and readjustments of, the nerve-centres

must take place without any disturbance of the other necessary

adjustments already attained. This is no simple problem.

We will here neglect the fact that many other changes are going on

simultaneously. Legs are being formed or moulded into jaws, the

anterior segments are fusing into a head, and their ganglia into a

brain; an external skeleton is developing. Furthermore the increase

of the muscular and nervous systems must be accompanied by increased

powers of digestion, respiration, and excretion. Practically the

whole body is being recast. We insist only on the necessity of

simultaneous and parallel changes in muscles, nerves, and

nerve-centres; though what is true of these is true, in greater or

less degree, of all the other organs.

You may answer that this is to be explained by the law of

correlation of organs; that when changes in one organ demand

corresponding changes in another, these two change similarly and

more or less at the same time and rate. But this is evidently not an

explanation but a restatement of the fact. The question remains,

What makes the organs vary simultaneously so as to always correspond

to each other? The whole series of changes must to some extent be

effected at once and in the same individual, if it is to be

preserved by natural selection. Fortuitous variations here and there

along the line of the series are of little or no avail. That the

whole series of variations should happen to occur in one animal is

altogether against the law of probabilities; if the favorable

variation occurs in only a part of the series it remains useless

until the corresponding variation has taken place in the other

terms. And while the variation is thus awaiting its completion, so

to speak, it is useless, and cannot be fostered by natural

selection.

Evolution by means of fortuitous variations, combined and controlled

only through natural selection, seems to me at least impossible; and

this view is, I think, steadily gaining ground.

Natural selection, while a real and very important factor in

evolution, cannot be its sole and exclusive explanation. It

presupposes other factors, which we as yet but dimly perceive. And

this does not impeach the validity of Mr. Darwin's theory any more

than Newton's theory of gravitation is impeached by the fact that it

offers no explanation as to why the apple falls or how bodies

attract one another.

For natural selection explains the survival, but not the origin, of

the fittest. Given a species or other group composed of more and

less fit individuals and the fittest will survive. How does it come

about that there are any more and less fit individuals? This brings

us to the consideration of the subject of variation.

Let us begin with a simple case of change in the adult body. The

workman grasps his tools day after day, and his hands become horny.

The skin has evidently thickened, somewhat as on the soles of the

feet. This is no mere mechanical result of pressure alone.

Continuous pressure would produce the opposite result. But under the

stimulus of intermittent pressure the capillaries, or smallest blood

vessels, furnish more nutriment to the cells composing the lowest

layer of the outer skin or epidermis. These cells, being better

nourished, reproduce by division more rapidly, and the epidermis,

becoming composed of a greater number of layers of cells, thickens.

The outer-most layers, being farthest from the blood supply, dry up

and are packed together into a horny mass.

If I go out into the sunshine I become tanned. This again is not a

direct and purely chemical or physical result of the sun's rays, but

these have stimulated the cells of the skin to undergo certain

modifications. Any change in the living body under changed

conditions is not passive, but an active reaction to a stimulus

furnished by the surroundings. The same stimulus may excite very

different reactions in different individuals or species.

Early in this century a farmer, Seth Wright, found among his lambs a

young ram with short legs and long body. The farmer kept the ram,

reasoning that his short legs would prevent him from leading the

flock over the farm-walls and fences. From this ram was descended

the breed of ancon, or otter, sheep. Now the stimulus which had

excited this variation must have been applied early in embryonic

life, or perhaps during the formation or maturing of the germ-cells

themselves. Such a variation we call a congenital variation.

These cases are merely illustrations of the general truth that in

every variation there are two factors concerned: the living being

with its constitution and inherent tendencies and the external

stimulus.

The courses of the different balls in a charge of grape-shot, hurled

from a cannon, are evidently due to two sets of forces--1, their

initial energy and the direction of their aim; 2, the deflecting

power of resisting objects or forces--or the different balls might

roll with great velocity down a precipitous mountain-side. In the

first case velocity and direction of course would be determined

largely by initial impulse; in the second, by the attraction of the

earth and by the inequalities of its surface.

In evolution, environment, roughly speaking, corresponds to these

deflecting or attracting external objects or forces; inherent

tendencies to initial impulse. If we lay great weight on initial

tendencies, inherent in protoplasm from the very beginning, we shall

probably lay less stress on natural selection as a guiding,

directing process.

The great botanist, Nägeli, has propounded a most ingenious and

elaborate theory of evolution, as dependent mainly on inherent

initial tendency. We can notice only one or two of its salient

points. All development is, according to his view, due to a tendency

in the primitive living substance toward more complete division of

labor and greater complexity. This tendency, which he calls

progression, or the tendency toward perfection, is the result of the

chemical and molecular structure of the formative controlling

protoplasm (idioplasm) of the body, and is transmitted with other

parental traits from generation to generation. And structural

complexity thus increases like money at compound interest.

Development is a process of unfolding or of realization of the

possibilities of this tendency under the stimulus of surrounding

influences. Environment plays an essential part in his system. But

only such changes are transmissible to future generations as have

resulted from modifications arising in the idioplasm. Descendants of

plants which have varied under changed conditions revert, as a rule,

to the old type, when returned to the old surroundings. And in the

animal world effects of use and disuse are, according to his view,

not transmissible.

Natural selection plays a very subordinate part. It is purely

destructive. Given an infinity of place and nourishment--do away,

that is, with all struggle and selection--and the living world would

have advanced, purely by the force of the progressive tendency, just

as far as it now has; only there would have survived an indefinite

number of intermediate forms. It would have differed from our

present living world as the milky way does from the starry

firmament.

He compares the plant kingdom to a great, luxurious tree, branching

from its very base, whose twigs would represent the present stage of

our different species. Left to itself it would put out a chaos of

innumerable branches. Natural selection, like a gardener, prunes the

tree into shape. Children might imagine that the gardener caused the

growth; but the tree would have been broader and have branched more

luxuriantly if left to itself.[A]

[Footnote A: See Nägeli, "Theorie der Abstammungslehre," p. 18;

also pp. 12, 118, 285.]

Every species must vary perpetually. Now this proposition is

apparently not in accord with fact; for some have remained unchanged

during immense periods. And natural selection, by removing the less

fit, certainly appears to contribute to progress by raising the

average of the species. The theory seems extreme and one-sided. And

yet it has done great service by calling in question the

all-sufficiency of natural selection and the modifying power of

environment, and by emphasizing, probably overmuch, the importance

of initial inherent tendency, whose value has been entirely

neglected by many evolutionists.

Lack of space compels us to leave unnoticed most of the exceedingly

valuable suggestions of Nägeli's brilliant work.

It is still less possible to do any justice in a few words to

Weismann's theory. Into its various modifications, as it has grown

from year to year, we have no time to enter. And we must confine

ourselves to his views of variation and heredity.

In studying protozoa we noticed that they reproduced by fission,

each adult individual dividing into two young ones. There is

therefore no old parent left to die. Natural death does not occur

here, only death by violence or unfavorable conditions. The protozoa

are immortal, not in the sense of the endless persistence of the

individual, but of the absence of death. Heredity is here easily

comprehensible, for one-half, or less frequently a smaller fraction,

of the substance of the parent goes to form the new individual.

There is direct continuity of substance from generation to

generation.

But in volvox a change has taken place. The fertilized egg-cell,

formed by the union of egg and spermatozoon, is a single cell, like

the individual resulting from the conjugation or fusion of two

protozoa. But in the many-celled individual, which develops out of

the fertilized egg, there are two kinds of cells. 1. There are other

egg-cells, like the first, each one of which can, under favorable

conditions, develop into a multicellular individual like the

parent. And the germ-cells (eggs and spermatozoa) of volvox are

immortal like the protozoa. But, 2, there are nutritive, somatic

cells, which nourish and transport the germ-cells, and after their

discharge die. These somatic cells, being mortal, differ altogether

from the germ-cells and the protozoa. The protoplasm must differ in

chemical, or molecular, or other structure in the two cases, and we

distinguish the germ-plasm of the germ-cells, resembling in certain

respects Nägeli's idioplasm, from somatoplasm, which performs most

of the functions of the cell. The somatoplasm arises from, and hence

must be regarded as a modification of, the germ-plasm. The

germ-plasm can increase indefinitely in the lapse of generations,

increase of the somatoplasm is limited.

When a new individual develops, a certain portion of the germ-plasm

of the egg is set aside and remains unchanged in structure. This,

increasing in quantity, forms the reproductive elements for the next

generation. The germ-plasm, which does not form the whole of each

reproductive element, but only a part of the nucleus, is thus an

exceedingly stable substance. And there is a just as real continuity

of germ-plasm through successive generations of volvox, or of any

higher plants or animals, as in successive generations of protozoa.

In certain plants there is an underground stem or rootstock, which

grows perennially, and each year produces a plant from a bud at its

end. This underground rootstock would represent the continuous

germ-plasm of successive generations; the plants which yearly arise

from it would represent the successive generations of adult

individuals, composed mainly of somatoplasm. Or we may imagine a

long chain, with a pendant attached to each tenth or one-hundredth

link. The links of the chain would represent the series of

generations of germ-cells; the pendants, the adults of successive

generations.

But any leaf of begonia can be made to develop into a new plant,

giving rise to germ-cells. Here there must be scattered through the

leaves of the plant small portions of germ-plasm, which generally

remain dormant, and only under special conditions increase and give

rise to germ-cells.

A large part of the germ-plasm of the fertilized egg is used to give

rise to the somatoplasm composing the different systems of the

embryo and adult. Weismann's explanation of this change of

germ-plasm into somatoplasm is very ingenious, and depends upon his

theory of the structure of the germ-plasm; and this latter theory

forms the basis of his theory of evolution. It would take too long

to state his theory of the structure of germ-plasm, but an

illustration may present fairly clear all that is of special

importance to us.

The molecules of germ-plasm are grouped in units, and these in an

ascending series of units of continually increasing complexity,

until at last we find the highest unit represented in the nucleus of

the germ-cell. This grouping of molecules in units of increasing

complexity is like the grouping of the men of an army in companies,

regiments, brigades, divisions, etc.

To form the somatoplasm of the different tissues of the body, this

complicated organization breaks up, as the egg divides, into an

ever-increasing number of cells. First, so to speak, the corps

separate to preside over the formation of different body regions.

Then the different divisions, brigades, and regiments, composing

each next higher unit, separate, being detailed to form ever

smaller portions of the body. The process of changing germ-plasm

into somatoplasm is one of disintegration. The germ-plasm

contains representatives of the whole army; a somatic cell only

representatives of one special arm of a special training. Germ-plasm

in the egg is like Humpty-Dumpty on the wall; somatoplasm, like

Humpty-Dumpty after his great fall.

I use these rude illustrations to make clear one point: Germ-plasm

can easily change into somatoplasm, but somatoplasm once formed can

never be reconverted into germ-plasm, any more than the fallen hero

of the nursery rhyme could ever be restored.

The germ-plasm is, according to Weismann, a very peculiar, complex,

stable substance, continuous from generation to generation since the

first appearance of life on the globe. It is in the body of the

parent, but scarcely of it. Its relation to the body is like that of

a plant to the soil or of a parasite to its host. It receives from

the body practically only transport and nourishment. It is like a

self-perpetuating, close corporation; and the somatoplasm has no

means of either controlling it or of gaining representation in it.

Says Weismann[A]: "The germ-cells are contained in the organism, and

the external influences which affect them are intimately connected

with the state of the organism in which they lie hid. If it be well

nourished, the germ-cells will have abundant nutriment; and,

conversely, if it be weak and sickly, the germ-cells will be

arrested in their growth. It is even possible that the effects of

these influences may be more specialized; that is to say, they may

act only upon certain parts of the germ-cells. But this is indeed

very different from believing that the changes of the organism which

result from external stimuli can be transmitted to the germ-cells

and will redevelop in the next generation at the same time as that

at which they arose in the parent, and in the same part of the

organism."

[Footnote A: Essays upon Heredity, p. 105.]

But if the germ-plasm has this constitution and relation to the rest

of the body, how is any variation possible? Different individuals of

any species have slightly different congenital tendencies. Hence in

the act of fertilization two germ-plasms of slightly different

structure and tendency are mingled. The mingling of the two produces

a germ-plasm and individual differing from both of the parents.

Thus, according to Weismann's earlier view, the origin of variation

was to be sought in sexual reproduction through the mingling of

slightly different germ-plasms.

But how did these two germ-plasms come to be different? How was the

variation started? To explain this Weismann went back to the

unicellular protozoa. These animals are undoubtedly influenced by

environment and vary under its stimuli. Here the variations were

stamped upon the germ-plasm, and the commingling of these variously

stamped germ-plasms has resulted in all the variations of higher

animals.

Of late Weismann has modified and greatly improved this portion of

his theory. He now accepts the view that external influences may act

upon the germ-plasm not only in protozoa but also in all higher

animals. Variation is thus due to the action or stimulus of

external influences, supplemented by sexual reproduction.

But the very constitution of the germ-plasm and its relation to the

body absolutely forbids the transmission of acquired somatic

characteristics and of the special effects of use and disuse.

Muscular activity promotes general health, and might thus conduce to

better-nourished germ-cells and to more vigorous and therefore

athletic descendants. The exercise of the muscles might possibly

cause such a condition of the blood that the portion of the

germ-plasm representing the muscular system of the next generation

might be especially nourished or stimulated. Thus an athletic parent

might produce more athletic children.

But let us imagine twin brothers of equal muscular development. One

from childhood on exercises the lower half of his body; the other,

the upper. Both take the same amount of exercise, and have perhaps

equal muscular development, but located in different halves of the

body. Now it is hard to conceive that it can make any difference in

the nourishing or stimulating influence of the blood, whether the

muscular activity resides in one half of the body or the other. The

children might be exactly alike.

One man drives the pen, a second plays the piano, and a third wields

a light hammer. All three use different muscles of the hand and arm.

How can this use of special muscles stamp itself upon the germ-cells

in such a way that the offspring will have these special muscles

enlarged? Granting that external influences of environment and

bodily condition may effect the germ-cells; granting even that some

of the most general effects of use and disuse might be transmitted,

what warrant have we for believing that the special acquired

characteristic can be transmitted? Weismann answers, None at all.

The somatoplasm can only in the most general way affect the

self-perpetuating, close corporation of the germ-plasm.[A]

[Footnote A: Weismann, Essays, p. 286.]

There is thus, according to Weismann, nothing to direct variation to

certain organs, or to guide and combine the variations of these

organs along certain lines, except natural selection. To a certain

extent variation may be limited by the very structure of the animal.

But within these limits there are wide ranges where one variation is

apparently just as likely to occur as another.

Within these wide limits variation appears to be fortuitous. Natural

selection must wait until the individuals appear in which these

variations occur already correlated, and then seize upon these

individuals. It is apparently the only guiding, directing force.

Linear variation, that is, a variation advancing continuously along

one or very few straight lines, would appear to be impossible.

In Nägeli's theory initial tendency is overwhelmingly dominant; in

Weismann's, natural selection is almighty.

Weismann's followers have received the name of Neo-Darwinians. The

so-called Neo-Lamarckian school believes in the transmissibility of

acquired characteristics, and of at least particular effects of use

and disuse. The one theory is neither more nor less Darwinian than

the other. For while Darwin emphasized natural selection, he

accepted to a certain extent the transmission of special effects of

use and disuse.

A special theory of heredity, pangenesis, has been accepted by many

of the Neo-Lamarckian school. The theory of pangenesis, as

propounded by Mr. Darwin, may be very briefly stated as follows: The

cells in all parts of the body are continually throwing off germinal

particles, or "gemmules." These become scattered through the body,

grow, and multiply by division. On account of mutual attraction they

unite in the reproductive glands to form eggs or spermatozoa. The

germ-cells are thus the bearers of heredity because they contain

samples, so to speak, of all the organs of the body.

In heredity, according to Weismann's theory, the egg is the centre

of control, the continuous germ-plasm the source of all transmitted

changes; according to Darwin's theory, the body is the source, and

the egg is derived in great part at least from it. If you put to the

two the time-honored question, Which is first, the owl or the egg?

Weismann would announce, with emphasis, The egg; Darwin would say,

The owl. One proposition is the converse of the other, and most

facts accord almost equally well with both theories.

In any family, devoted for generations to literary or artistic

pursuits, the children show, as a rule, an aptitude for such

pursuits not manifested by those of other families. According to the

Neo-Lamarckian view, this inherited aptitude is to a certain extent

the result of the constant exercise of these faculties through a

series of generations. The active efforts and voluntary disposition

of the parents have given an increased predisposition to the child.

"Quite the reverse," says Weismann, "the increase of an organ in the

course of generations does not depend upon the summation of

exercise taken during single lives, but upon the summation of more

favorable predispositions in the germ." "An organism cannot acquire

anything unless it already possesses the predisposition to acquire

it."[A]

[Footnote A: Weismann, Essays, pp. 85 and 171.]

We may accept or deny this last statement, but it is evident

that facts like these, and indeed the origin of most or all

characteristics involving use or disuse, may be explained almost

equally well by either theory.

But as far as the transmission of effects of somatic changes is

concerned, if protozoa undergo special modifications under the

influence of external conditions, will not the germ-cells undergo

special modification under the influence of changes in the

somatoplasm which forms their immediate environment? We must never

forget the close relationship between all the cells of the body, and

how slight a change in the body or its surroundings may conduce to

sterility or fertility. Such isolation and independence in the body,

on the part of the germ-cells, is opposed to all that we know of the

organic unity of the body, whose cells have arisen by the

differentiation of, and division of labor between, cells primitively

alike. The facts of bud-variation, of changes in the parent stock

due to grafting, and others, of which Mr. Darwin has given a summary

in the eleventh chapter of the first volume of his "Plants and

Animals under Domestication," have never been adequately explained

by Weismann in accordance with his theory. He has perhaps succeeded

in parrying their force by showing that some such explanation is

conceivable; they still point strongly against him.

Wilson has good reason for his "steadily growing conviction that

the cell is not a self-regulating mechanism in itself, that no cell

is isolated, and that Weismann's fundamental proposition is false."

But, granting the force of these criticisms, the question still

remains, Is the special effect of use or disuse transmissible? Would

the blacksmith's son have a stronger right arm?

1. The isolation and independence of the germ-cells, which Weismann

postulates as opposing this, can hardly be as great as he thinks. 2.

It is in his view impossible to conceive how these acquired

characteristics can in any way reach and affect the germ-cells in

such a manner as to reappear in the next generation. 3. All

variations can be explained by his own theory without such

transmission. Why then believe that acquired characteristics can in

some inconceivable way affect the germ-cells so as to reappear in

the next generation, as long as all the facts can be explained in a

more simple and easily conceivable manner?

As to his second argument, I would readily acknowledge that it is at

present difficult or impossible for me to conceive how any cell can

act upon another, except through the nutrient or other fluids which

it can produce. But though I cannot conceive how one cell can affect

another, I may be compelled to believe that it does so. And this

Weismann readily acknowledges.

Driesch changed by pressure the relative position of the cells of a

very young embryo, so that those which in a normal embryo would have

produced one organ were now compelled, if used at all, to form quite

a different one. And yet these displaced cells formed the organ

required of cells normally occupying this new position, not the one

for which they were normally intended. And the organ which they

would have builded in a normal embryo was now formed by other cells

transferred to their rightful place.

What made them thus change? Not change of substance or structure,

for the slight pressure could hardly have modified this. Not change

of nutriment. The only visible or easily conceivable change was in

position relative to other cells of the embryo.

Let us in imagination simplify Driesch's experiment, for the sake of

gaining a clearer view of its meaning. In a certain embryo at an

early stage are certain cells whose descendants should form the

lining of the intestine and be used in the adult for digestion. A

second set of cells should form muscle endowed mainly with

contractility. When these two sets of cells, or some of them,

exchange positions in the embryo, they exchange lines of

development. The first set now form muscle, the second digestive

tissue. The only change has been in their relative positions.

Driesch maintains, therefore, that the goal of development in any

embryonic cell is determined not by structure or nutriment but by

position. And this would seem to be true of the cells of the

earliest embryonic stages.

Certain other experiments point in the same direction. Cut a hydra

into equal halves and each half will form a complete animal. The

lower half forms a new top, with mouth and tentacles; the upper

half, a new base. Cut the other hydra a hair's-breadth farther up.

The same layer of cells which in the first animal formed the lower

exposed surface of the upper half now forms the upper exposed

surface of the lower half. And with this change of position it has

changed its line of development; it will now give rise to a new

upper half, not a base as before. The same experiment can be tried

on certain worms with similar results, only head and tail differ far

more than top and base of hydra. Difference in the position of cells

has made vast difference in their line of development. Now in both

embryo and adult there must be some directing influence guiding

these cells. What is it?

An army is more than a mob of individuals; it is individuals plus

organization, discipline, authority. A republic is not square miles

of territory and thousands or millions of inhabitants. It is these

plus organization, central government. Webster claimed that the

central government was, and had to be, before the states. The

organism cannot exist without its parts; it has a very real

existence in and through them. It can coerce them. The state may be

an abstraction, but it is one against which it is usually fatal to

rebel, and which can say to a citizen, Go and be hanged, and he

straightway mounts the scaffold. Now these are analogies and prove

nothing. But in so far as they throw light on the essential idea of

an organism, they may aid us in gaining a right view of our "cell

republic."

Says Whitman in a very interesting article on the "Inadequacy of the

Cell-Theory": "That organization precedes cell-formation and

regulates it, rather than the reverse, is a conclusion that forces

itself upon us from many sides." "The structure which we see in a

cell-mosaic is something superadded to organization, not itself the

foundation of organization. Comparative embryology reminds us at

every turn that the organism dominates cell-formation, using for

the same purpose one, several, or many cells, massing its material

and directing its movements, and shaping its organs as if cells did

not exist, or as if they existed only in complete subordination to

its will, if I may so speak. The organization of the egg is carried

forward to the adult as an unbroken physiological unity, or

individuality, through all modifications and transformations." And

Wilson, Whitman, Hertwig, and others urge "that the organism as a

whole controls the formative processes going on in each part" of the

embryo. And many years ago Huxley wrote, "They (the cells) are no

more the producers of the vital phenomena than the shells scattered

along the sea-beach are the instruments by which the gravitative

force of the moon acts upon the ocean. Like these, the cells mark

only where the vital tides have been, and how they have acted."[A]

[Footnote A: See articles by Whitman and Wilson, Journal of

Morphology, vol. viii., pp. 649, 607, etc.]

"Interaction of cells" can help us but little. For how can

neighboring cells direct others placed in a new position? The

expression, if not positively misleading and untrue, is at the best

only a restatement of fact. It certainly offers no explanation.

Flood-tide is not due to the interaction of particles of water,

though this may influence the form of the waves.

The centre of control is therefore not to be sought in individual

cells, whether germ-cells or somatic, but in the organism. And it is

the whole organism, one and indivisible, which controls in germ,

embryo, and adult, in egg and owl. This individuality, or whatever

you will call it, impresses itself upon developing somatic cells,

moulding them into appropriate organs, and upon germ-cells in

process of formation, moulding them so that they may continue its

sway. The muscle, modified by use or disuse, is a better expression

of the individuality of its possessor, and the same individuality

moulds similarly and simultaneously the germ-cells. Both are

different expressions or manifestations of the same individuality.

Only slowly does the individuality mould the muscles and nerves of

the adult body to its use. Still more slow may be the moulding of

the still more refractory germ-plasm, if such there be. But the

moulding process goes on parallel in the two cases.

But Weismann's argument rests not merely upon any difficulty or

impossibility of the transmissibility of acquired characteristics.

His argument is rather that all facts can be better explained by his

theory without postulating or accepting such transmission, cases of

which have never been absolutely proven. But the question is not

whether his theory offers a possible explanation of the facts, but

whether it is the most probable explanation of all the facts. No one

would deny, I think, that the continuity of the germ-plasm offers

the best and most natural explanation of heredity; and that

variations could be produced by the influence on the germ-plasm of

external conditions seems entirely probable.

But when we consider the aggregation of these variations in a

process of evolution, his theory seems unsatisfactory. We have

already seen that what we commonly call a variation involves not one

change, but a series of changes, each term of which is necessary.

Muscle, nerve, and ganglion must all vary simultaneously and

correspondingly. Correlation and combination are just as essential

as variation. And evolution often demands the disappearance of less

fit structures just as much as the advance of the fittest. Says

Osborne, "It is misleading to base our theory of evolution and

heredity solely upon entire organs; in the hand and foot we have

numerous cases of muscles in close contiguity, one steadily

developing, the other degenerating." Weismann offers the explanation

that "if the average amount of food which an animal can assimilate

every day remains constant for a considerable time, it follows that

a strong influx toward one organ must be accompanied by a drain upon

others, and this tendency will increase, from generation to

generation, in proportion to the development of the growing organ,

which is favored by natural selection in its increased blood-supply,

etc.; while the operation of natural selection has also determined

the organ which can bear a corresponding loss without detriment to

the organism as a whole."[A]

[Footnote A: Weismann, Essays, p. 88.]

Here again natural selection of individuals, not the diminished

supply of nutriment, has to determine which of many muscles shall be

poorly fed and which favored. But natural selection can favor

special organs only indirectly through the individuals which possess

such organs. Variation is fortuitous, and there is nothing, except

natural selection, to combine or direct them. And, I think, we have

already seen that any theory which neglects or excludes such

directing and combining agencies must be unsatisfactory and

inadequate. Weismann has promised us an explanation of correlation

of variation in accordance with his theory; and if such an

explanation can be made, it would remove one of the strongest

objections. But for the present the objection has very great weight.

Furthermore, as Osborne has insisted, linear variations, or

variations proceeding along certain single and well-marked lines,

would seem inexplicable by, if not fatal to, Weismann's theory. And

yet Osborne, Cope, and others have shown that the teeth of mammals

have developed steadily along well-marked lines. They have

apparently not resulted at all by selection from a host of

fortuitous variations.

Says Osborne in his "Cartwright Lectures"[A]: "It is evident that

use and disuse characterize all the centres of evolution; that

changes of structure are slowly following on changes of function or

habit. In eight independent regions of evolution in the human body

there are upward of twenty developing organs, upward of thirty

degenerating organs." Now this parallelism, through a long series of

generations, between the evolution of organs, their advance or

degeneration, and the use or disuse of these same organs, that is,

of the habits of the individual, is certainly of great significance.

It must have an explanation; and the most natural one would seem to

be the transmission of the effects of use and disuse.

[Footnote A: American Naturalist, vols. xxv. and xxvi.]

On the whole Osborne's verdict would seem just: The Neo-Lamarckian

theory fails to explain heredity, Weismann's theory does not explain

evolution. But, if the effects of use and disuse are transmitted,

correlation of variation is to be expected. Muscle, nerve, and

ganglion all vary in correlation because they are all used together

and in like degree. Evolution and degeneration of muscles in hand

and foot go on side by side, because some are used and some are

disused. Centres of use and disuse must be centres of evolution. And

there would be as many distinct centres of evolution in different

parts of the body as there were centres of use and disuse. And

between these centres there might be no correlation except

that of use and disuse. Brain, muscles, and jaws would develop

simultaneously in the ancestors of insects. And the effects of use

and disuse, transmitted through a series of generations, would be

cumulative. The species advances rapidly because all its members

have in general the same habits; the same parts are advancing or

degenerating, although at different rates, in all its individuals.

An animal having an organ highly developed is far less likely to

pair with one having a lower development of the same organ. The

Neo-Lamarckian theory supplies thus what is lacking in the

Neo-Darwinian.

In lower forms, like hydra, of simple structure and comparatively

few possibilities of variation, natural selection is dominant. In

higher forms, like vertebrates, and especially in man, it is of

decidedly subordinate value as a promoter of evolution. For man, as

we have seen, is a marvellously complex being. The great difficulty

in his case is not so much to quickly gain new and favorable

variations as to keep all the organs and powers of the body steadily

advancing side by side. Natural selection has in man the important

but subordinate position of the judge in a criminal court, to

pronounce the death verdict on the hopeless and incorrigible.

Both Neo-Darwinians and Neo-Lamarckians have erred in being too

exclusively mechanical in their theories. It is the main business of

the scientific man to discover and study mechanisms. But he must

remember that mechanism does not produce force, it only transmits

it. If he maintains that he has nothing to do with anything outside

of mechanism, that the invisible and imponderable force lies outside

of his domain, he has handed over to metaphysics the fairest and

richest portion of his realm. In our fear of being metaphysical we

have swung to another extreme, and have lost sight of valuable truth

which lay at the bottom of the old vitalistic theories. Cells,

tissues, and organs are but channels along which the flood of

life-force flows. Boveri has well said, "There is too much

intelligence (Verstand) in nature for any purely mechanical theory

to be possible."

Each theory contains important truth. Nägeli's view of the

importance of initial tendencies, inherent in the original living

substance, is too often undervalued. My own conviction, at least, is

steadily strengthening that, without some such original tendency or

aim, evolution would never have reached its present culmination in

man. His error lies in emphasizing this factor too exclusively. The

fundamental proposition of Weismann's theory, that heredity is due

to continuity of germ-plasm, seems to contain important truth. But

we need not therefore accept his theory of a germ-plasm so isolated

and independent as to be beyond control or influence by the

habits of the body. The importance of use and disuse, and the

transmissibility of their effects, would seem to supply a factor

essential to evolution. Weismann has done good service in

emphasizing the stability of the germ-plasm. Evolution is always

slow, and, for that very reason, sure.

If these conclusions are correct, they have an important practical

bearing. Struggle and effort are essential to progress. Not inborn

talent alone, but the use which one makes of it, counts in

evolution. The effects of use and disuse are cumulative. The

hard-fought battle of past generations becomes an easy victory in

the present, just because of the strength acquired and handed down

from the past struggle. Persistent variation toward evil is in time

weeded out by natural selection. And, while evil remains in the

world, we are to lay up stores of strength for ourselves and our

descendants by sturdily fighting it. But the effects of right living

through a hundred generations are not overcome by the criminal life

of one or two. Evil surroundings weigh more in producing criminals

than heredity, and their children are not irreclaimable.

The struggles and victories of each one of us encourage the rest.

There is, to borrow Mr. Huxley's language, not only a survival of

the fittest, but a fitting of as many as possible to survive. And in

the midst of the hardest struggle there is the peace which comes

from the assurance of a glorious triumph.

Condensed Chart of Development of the Main Line

of the Animal Kingdom leading to Man.

| | ORGANS | MOST RAPIDLY

PHYLOGENETIC | | APPROACHING | ADVANCING

SERIES. | NEW ATTAINMENTS. | CULMINATION. | ORGANS.

-------------+----------------------------+---------------+--------------

Amoeba. | Cell. | |

-------------+----------------------------+---------------+--------------

Volvox. | Somatic and reproductive | | Reproductive.

| cells | |

-------------+----------------------------+---------------+--------------

Hydra. | Simple reproductive organs.| | Reproductive.

| Gastro vascular cavity. | |

| (Tissues). | |

-------------+----------------------------+---------------+--------------

Turbellaria. | D | Complex reproductive | Reproductive. | Digestive.

| e | Organs. Supra-oes. | |

| v | Ganglion and cords. | |

| e | Sense organs. | |

| l | Body wall.ns. | |

| o | | |

| p | | |

-------------+---|------------------------+---------------+--------------

Annelid. | O | Perivisceral Cavity. | |

| r | Intestine. Circulatory | |

| g | system. Nephridia. | |

| a | Visual eyes. | |

| n | | |

| s | | |

-------------+---+------------------------+---------------+--------------

Primitive | Notochord. Fins. | |

Vertebrate. | | |

-------------+----------------------------+---------------+--------------

Fish. | Backbone (incomplete). | Digestive. | Muscles.

| Paired Fins. Jaws from | |

| Branchial Arches. Simple | |

| heart. Air Bladder. Brain. | |

-------------+----------------------------+---------------+--------------

Amphibian. | Legs. Lungs. Cerebrum | | Muscles.

| increases from this | |

| form on. | |

-------------+----------------------------+---------------+--------------

Reptile. | Double heart. | | Muscles and

| | | appendages.

-------------+----------------------------+---------------+--------------

Lower | Constant high temperature | | Muscles and

Placental | Placenta. | Muscle. | appendages.

Mammals. | | |

-------------+----------------------------+ +--------------

Ape. | Erect posture. Hand. Large | | Brain.

| cerebrum. | |

| | |

-------------+----------------------------+---------------+--------------

Man. | Very large cerebrum. | | BRAIN.

| Personality. | |

| | |

-------------+----------------------------+---------------+--------------

[Table continued below]

+-------------+---------------+--------------+---------------+-------------

+-------------+---------------+--------------+---------------+-------------

| | | | |

+-------------+---------------+--------------+---------------+

| | | | |

| | | | |

+-------------+---------------+--------------+---------------+-------------

T| | | | |

| | | | |

+-------------+---------------+--------------+---------------|reproduction

n| | | | |

| | | | |

+-------------+---------------+--------------+---------------|

P| Digestion | Instinct. | ? | |

V| Muscular. | | | |

+-------------+---------------+--------------+---------------+-------------

| | | | |

+-------------+---------------+--------------|Fear and |

+-------------+---------------+--------------| |

+-------------+---------------+--------------| |

P| | | Sight. | |

M| | | | |

+-------------+---------------+--------------+---------------+-------------

p| | |Understanding.| |

e| | |Association. | |

+-------------+---------------+--------------+---------------+-------------

a| | | | Right.* | and

n| | | | |unelfishness*

+-------------+---------------+--------------+---------------+-------------

* Apparently capable of indefinite development.

PHYLOGENETIC CHART OF PRINCIPAL TYPES OF ANIMAL LIFE.

_____________________________________________________

Man.

/|\

| Apes.

\ | /

\|/

Lower Placental Mammals.\ |

\ |

Marsupial Mammals.\ |

\ |

Oviparous Mammals.\ \| /Birds.

\ | /

| /Reptiles.

| /

Ampibia.\ |/

\ |

Insect.\ |

\ |

\ | /Fish.

\ | /

\ | / /Mollusca.

\ | / /

Annelid.------\ | / /

\ |/ /

\ | /

| /

Schematic Worm.\ | /

\ | /

\ | / /Turbellaria.

\| /

| /

Hydra.\ | /

\ | /

\ |/

\ |

| /Volvox.

| /

Magosphaera.\ | /

\ |/

\ |

\| /Amoeba.

| /

_____________________________________________________

PHYLOGENETIC CHART OF PRINCIPAL TYPES OF

ANIMAL LIFE.

_____________________________________________________

INDEX

Amoeba, 32

Annelids, 61, 103

Apes, anthropoid, 91

Appetites, 137

Arthropoda, 61

Articulata, 61

Beauty, perception of, 121

Bible, 241

Blastosphere, 44

Brain, 64, 108;

of insects, 69;

vertebrates, 75, 85;

man, 96.