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The story of Roosevelt's life is told, and we realize that his spoken and written words have often stood concrete results of his own vivid experience as boy and man. Those who know the facts will recognize the following as autobiographical: "I would order them [young men] to work . . . I would teach the young man that he who has not wealth owes his first duty to his family, but he who has means owes his to his State . . . I would preach the doctrine of work to all, and to the man of wealth the doctrine of unremunerative work.'

"Of course, what we have a right to expect of the American boy is that he shall turn out to be a good American man. Now, the chances are strong that he won't be much of a man unless he is a good deal of a boy. He must not be a coward or a weakling, a bully, a shirk, or a prig. He must work hard and play hard. He must be clean-minded and clean-lived, and able to hold his own under all circumstances and against all comers."

"In life as in a football game, the principle to follow is: Hit the line hard; don't foul and don't shirk, but hit the line hard."-From. "The American Boy," 1900.

In such plainly spoken words as these the spirit of Roosevelt will live for innumerable future generations of Americans.

Among all his messages perhaps none is more important in the light of the present speed at which civilization is having to settle difficult issues, than the following so often quoted from The Strenuous Life:

"In speaking to you, men who preeminently and distinctly embody all that is most American in the American character, I wish to preach, not the doctrine of ignoble ease, but the doctrine of the strenuous life, the life of toil and effort, of labor and strife; to preach the highest form of success which comes. . . to the man who does not shrink from danger, from hardship, or from bitter toil, and who out of these wins the splendid ultimate triumph. As it is with the individual, so it is

with the nation If we are to be a really great people, we must strive in good faith to play a great part in the world. We cannot avoid meeting great issues. All that we can determine for ourselves is whether we shall meet them well or ill. The twentieth century looms before us big with the fate of many nations. . If we shrink from the hard contests where men must win at hazard of their lives and at the risk of all they hold dear, then the bolder and stronger peoples will pass us by, and will win for themselves the domination of the world. Let us shrink from no strife,

moral or physical, within or without the nation, provided we are certain that the strife is justified, for it is only through hard and dangerous endeavor, that we shall ultimately win the goal of true national greatness."

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"The man who
works, the man
who does great
deeds, in the end
dies as surely as
the veriest idler
who cumbers the
earth's surface;
but he leaves be-
hind him the great
fact that he has
done his work
well. The Roman
passed away ex-
actly as all the na-
tions of antiquity
which did not

expand ..; but
their very mem-
ory has vanished,
while he himself
is still a living
force throughout
the wide world in
our entire civili-
zation of today.
"-From Roose-
velt's address on
"National Duties.
There is good
evidence that no
human beings of
recent times have
surpassed in in-
tellectual powers
various person-
ages of the o'd
Greek and Roman
civilizations; it
may be that even
the distant future
will hold no greater
geniuses than the
world already has
known. On the
other hand, the
future promises to
bring rapid evo-
lution in human
society and or.
ganization of
state: there is dis-

tinct prophecy in
Roosevelt's exam-
ple and urging to-
ward loyalty, mo-
rality and coöper-
ation, in social

and political rela-
tions, both na-
tional and inter-
national. Roose-
velt stood strongly
for the "League
of Nations"

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Has Progressive Evolution Come to an End?





Professor of Biology, Princeton University

HE term "evolution" is used in several senses. When considered in its larger aspects, as for example with respect to the increasing complexity of organization in the succession of life forms upon the earth, we are dealing with what may be called progressive organization or organic progress. When considered from the standpoint of increasing diversification, as shown in the appearance of varieties and species which are no more complex in organization than the forms from which they sprung and which may be even less complex, we have a type of evolution which is not progressive and which may be called speciation or diversification. A third aspect of evolution is that which deals with increasing adaptation to conditions of life and which may be called progressive adaptation; this may or may not be associated with progressive organization or with speciation.

Organization, of whatever kind, means differentiation and integration, specialization and coöperation, diversity and harmony. Progressive evolution invariably and inevitably means increasing differentiation and integration. In the long history of life upon the earth, organisms have varied in every possible way, they may be said to have made millions and millions of experiments in finding the path of progressive evolution, and in every instance this path has been in the direction of greater specialization and coöperation.

Millions of years ago unicellular organisms reached the utmost limits of the differentiations which were possible within a single cell. Thereafter a new

path had to be found if further advance in organization was to occur. This new path was found in the direction of multicellularity. Multicellular forms did not arise by the coming together of separate cells, as is sometimes assumed, but rather by the failure of cells to divide completely; when the original cell divided, the products no longer moved apart as separate and complete individuals but remained attached to one another, and instead of restoring all missing parts as each cell did when it became a separate and complete individual, the initial differences between cell products were preserved and increased at successive divisions. In this way entire cells became new units of differentiation and at the same time all the cells remained bound together into a unit of a higher order.

A wholly similar process of differentiation by cell formation takes place in the development of the egg; if cell formation is stopped in this case, differentiations never go beyond a stage comparable with those of the unicellular organism, and if the different cells fail to stick together they generally lose many of their differentiations and revert to the simpler organization of the egg. Whenever a complex protozoan divides, it goes back in organization to a more primitive condition, and after division it starts to differentiate over again; and so successive generations of protozoans make little or no advance in organization. But when the cells of a multicellular animal or plant divide they do not go back to the stage of differentiation of the egg but preserve the differentiations which they have al

ready attained and continue to augment them during the process of development. In multicellular organisms this increasing differentiation of the cells is made possible by the close union and interdependence of the cells, whereas in the unicellular forms the very independence of the cells prevents increasing differentiation.

In a manner wholly similar to the case of the one-celled forms multicellular organisms reach a stage of differentiation bevond which they cannot go within the limits of a single body. The very nature of differentiation signifies limitations in certain directions in order to secure further development in other directions. If a creature have wings it cannot also have hands (except in the case of the angels); if it have limbs for running it cannot also have limbs for swimming; if it have enormous strength it cannot also have great delicacy of movement. Thus while certain animals are differentiated in one direction and others in another, no one animal can be differentiated in all directions. In man differentiation has gone farthest in the structures and functions of the brain. In many other respects man is relatively undifferentiated; his limbs, hands and feet, his teeth and alimentary tract are far less highly differentiated than are these organs in many other animals, but his brain is much more highly differentiated. This very fact of a highly specialized nervous system and a generalized condition of many other organs has led to the wonderful intellectual and social evolution of man and has made possible not only the rational control of his own evolution but also the control of his environment.

Path of Social Evolution

Just as the multicellular condition. permits a higher degree of organization than is possible in the unicellular, so the union of multicellular organisms into a unit of a higher order opens up

a new path of evolution and progress. But here also, as in the former instance, the principles of progressive evolution are increasing differentiation and integration. In this way biological colonies or societies are formed, and in various animal societies one can trace the stages of social evolution from a condition in which all the individuals are much alike and the bond of union between them is a very loose one, to such societies as those of ants, bees, and termites in which the differentiations and integrations of individuals have gone much further even than in human society. We do not know whether progressive evolution of such animal societies has already reached its limits in colonies of ants and termites, but we do know that further evolution, if it occurs, must involve a still greater degree of differentiation and integration of individuals or of colonies.

Path of Intellectual Evolution

Meanwhile man has entered upon a new path of evolution, namely, the intellectual and ethical, and just as there was a great forward movement when the path of multicellularity was taken, and again when social organizations took the place of solitary individuals, so human advances in the path of intelligence and morality are perhaps the most significant in the whole range of organic evolution. Here, as in the cases of physical and social evolution, the factors or elements out of which the new organization is builded are present in the lowest and simplest forms of life, but it is only by the progressive differentiation and integration of these factors that progress is achieved.

The elements out of which the psychic faculties of man have been developed are present in all organisms, even in germ cells, in the form of sensitivity, tropisms, reflexes, organic memory, and a few other factors; in more complex animals these take the form of special senses, instincts, emotions and as


sociative memory; and in the highest animals, and especially in man, they blossom forth as intelligence, reason, will, and consciousness. All stages of this development may be seen in various animals below man and also in the development of the human personality from the germ cells.

No one knows whether human beings have already reached the limits of development of their intellectual, rational, and volitional powers. It is customary to assume that there is no limit to the possibilities of development in this direction, and certainly in the knowledge of and control over natural phenomena the most striking progress is now being made, chiefly, however, by coöperative effort. But this is not the question involved when we ask whether man has already reached the highest possible development of his intellectual and rational powers. There is good evidence that no recent human beings have surpassed in such powers many men of the ancient Greek race or many other individuals who have appeared in the past. Perhaps the intellectual evolution of man has already reached its climax in these greatest personages of history, so that even in the distant future there may never appear greater geniuses than Socrates, Plato and Aristotle, than Shakespeare, Newton and Darwin.

Path of Rational Coöperation Finally, a new path of evolution has been found by man in rational coöperation, that is in the further development of human society on a basis of intelligence rather than of instinct. Certainly in this direction the limits of human evolution have not been reached; indeed, it may be said that the rational evolution of society has barely begun. It is a notable fact that the social evolution of man is going forward at a very much more rapid rate than his physical or intellectual evolution.

In bodily structure and in intellectual capacity man has changed but


little since the beginnings of recorded history, but in social organization the most enormous advances have been made, and changes are still going on at a rate which is amazing if not alarming. The chief causes for this difference in the rate of physical and social evolution are to be found in the fact that individual experiences are more quickly and permanently impressed upon the intellect than upon the body or the instincts, and especially in the fact that through intelligent society past experiences are transmitted to future generations, each generation, as it were, standing upon the shoulders of the preceding one, whereas the physical man begins his development anew in each generation from the germ cells, and if he inherits any bodily features due to the experiences of his ancestors, a thing which seems most doubtful, they are very few and rare.

Progress Has Ceased in Many Lines

There is no probability that future. evolution will develop more complex animal or plant cells than those which now exist or have existed in the past;1 there is little likelihood that more complex multicellular forms than those which have lived or are now living will ever be evolved, for apparently the limits of complexity within a single cell or body have already been reached. Doubtless, both cells and bodies will continue to undergo changes which on the whole will lead to better adaptations to existing conditions, but such changes probably will be relatively slight as compared with the great evolutionary

1 Among animals no new phyla have appeared since the vertebrates in the Silurian, or perhaps even earlier; no new classes since the mammals in the Triassic and the birds in the Jurassic. In the evolution of animals only about fourteen times in the whole history of life have new phyletic paths been found and several of these were blind alleys which led nowhere. The climax of the progressive evolution of fishes was probably reached in the Devonian, of amphibians in the Permian, of reptiles in the Mesozoic. In all these classes the formation of new species has been going on more or less continuously, but progressive evolution in the sense of increasing complexity of organization has reached or passed its climax.

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