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MASSET SANDS

A. C. L.

The sun is bright on Masset strand,
The tide recedes invitingly.

Oh! Smooth and firm is the widening sand,
And smooth the gently heaving sea.

Across the strait the mountains loom,
Great sapphires in an azure sea;
Near by, the lowly roses bloom,
And little birds sing merrily.

In endless sweep the sands extend,
A path of gold all edged with white,
To where the sea and heavens blend,
Defined as gleam of meteor light.

The beach is fringed by brilliant green.
Beyond, in silent gloom arrayed,
Stand myriad trees of somber mien,

With never a glimpse of open glade.

And I am free to choose my way:

Sail out o'er the ocean's vast expanse,

Or through the forest toil I may,

Or golden path to heaven dance.

PRESENT TENDENCIES IN EVOLUTIONARY

THEORY

S. J. HOLMES

In attempting to give an idea of present tendencies in evolutionary speculation I can perhaps best proceed by recounting briefly some stages in the development of evolutionary theory since the publication of Darwin's Origin of Species in 1859. In the sixties and seventies interest was mainly centered in the establishment of the doctrine of organic evolution, in discovering new evidence for its support, in working out probable lines of descent among animals and plants, and in interpreting the facts of morphology, palaeontology, geographical distribution, and embryonic development from the evolutionary standpoint. This was a period of controversy in which the principle of evolution was gradually winning its way to general acceptance in the world of scholars. It is difficult for us, habituated to looking upon the world and its inhabitants as the outcome of a gradual development, to appreciate the profound changes which were then being wrought in man's outlook upon the problems of life, mind, and society. A great, new, and revolutionary conception of the origin of the existing order of the world of life was brought before the minds of all thinking human beings, filling some of them with apprehension and dismay, but powerfully stimulating others by its grandeur and far-reaching import.

Unlike the evolutionary speculations that preceded it, the doctrine set forth in the Origin of Species attracted

at once the attention of all serious thinkers. It was soon realized that the struggle between two rival world conceptions was on in earnest. Science had developed to such a point that the hypothesis of evolution could not remain as one among many mere guesses at the riddle of existence. It must be tested in the light of morphology, palaeontology, distribution, and embryology, and rejected if not proven worthy of acceptance by critical scholars. Darwin's great work supported the theory with a wealth of facts, drawn from a variety of fields, and marshalled with an ability that made it at once apparent to every scientifically trained person that he was face to face with a doctrine to be seriously grappled with. And it was not many years before the battle in behalf of the theory of evolution was won.

The influence of the writings of Darwin in compelling the acceptance of the theory of evolution was due not merely to the abundant evidence with which this doctrine was supported, but also to the fact that they set forth a good working hypothesis as to how and why evolution might have been brought about. The process of natural selection which Darwin regarded as the chief though not the sole cause of evolution presented at least an intelligible explanation of the development of the wonderful adaptions which form one of the most noteworthy features of the organic world. It was the apparent purposiveness manifested in the structure and activities of living beings that afforded the chief argument for the theory of special creation. The evidence of design and contrivance which organisms exhibit in such profusion had long been dwelt upon for the conIsolation of the faithful and the discomfiture of the skeptic. Now comes a theory which would eliminate teleological explanations in the realm of organic nature, and account for the development of life in terms of the survival of fortuitous variations in the struggle for existence.

Undoubtedly the great import of the theory of natural selection was that it afforded a means of explaining the development of structures exhibiting evidence of creative design in terms of processes which in themselves show no indication of purposive control. In other words, it afforded a very simple way of construing teleology in terms of mechanism. And whether or not we hold with Huxley that teleology received its death blow at Darwin's hands, it is evident that the theory of natural selection greatly aided the acceptance of the theory of evolution by showing how it was at least theoretically possible to explain by natural means the features of the organic world which had long been held up as incontestable evidences of creative design.

It is not my purpose to dwell upon the controversies over the fact of evolution, as this question is almost universally regarded as settled by the arguments of Darwin and by the vast amount of confirmatory evidence that has been accumulated in different fields by Darwin's coworkers and successors. I shall also pass over the progress that has been made in ascertaining the probable lines of descent of the various groups of animals and plants. And I shall omit all consideration of the light which the theory of evolution throws upon the problems, not only of biology, but of psychology, social science, ethics, and many other fields of human thought. My discussion will be limited to the method of evolution, not only because this problem is one of fundamental importance, but because there seems to be prevalent a remarkable amount of misunderstanding concerning the bearing of recent biological investigation on Darwin's theory.

The doctrine of natural selection early won and has always maintained a wide acceptance among biologists. I believe I am safe in saying that no other theory of the cause of evolution has ever been so widely accepted as the theory of natural selection. Darwin believed that

the transmission of acquired characteristics, whose importance in evolution had been emphasized by Lamarck, was a potent subsidiary factor, and he not infrequently appealed to it in order to help himself out of tight places. But since Weismann made his attack upon this doctrine during the eighties, belief in the transmission of acquired characteristics has steadily lost ground. The so-called neo-Darwinians, with their belief in the "all sufficiency of natural selection" (the phrase is Weismann's) form a flourishing school. During the two decades between 1880 and 1900 Professor Weismann, who was then perhaps the most influential figure in the field of evolutionary speculation, carried on a destructive criticism of the Lamarckian doctrine, and, at the same time, built up an elaborate theory of heredity and embryonic development, and manfully struggled to show how the principle of selection, reinforced by his subsidiary hypotheses of panmixia and germinal selection, affords a sufficient explanation for all the evolutionary changes in the world of life. What Romanes has called Weismannism has been a strong stimulus in directing thought and research into what have proved to be very fruitful fields. Weismann represented an extreme type of selectionist-but there are other biologists to whom Darwin's theory made little appeal. A few practically reject it entirely. Some orthogenesists and neo-Lamarckians ascribe to it a minor and merely negative rôle in killing off the weaker members of a species that fall below the average of fitness to their environment. Others, like Spencer, look upon it as an important factor in evolution but deem it obviously insufficient as a general explanation of either progressive or retrogressive development. And Alfred Russell Wallace, otherwise an orthodox neo-Darwinian, balks at admitting that it is capable of accounting for the development of the mental and moral faculties of man.

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