these elements, which, so far as we know, had never been in combined action before. He states that the thermal conditions of present-day living matter point to the probability that this coördinating of the "life elements" was initiated when portions at least of the earth's surface and waters had temperatures of between 6° and 89° C. and before the atmospheric vapors admitted a regular supply of sunlight. The earliest function of living matter appears to have been to capture and transform the electric energy of the chemical elements characteristic of protoplasm, and this power probably developed only in the presence of heat energy derived from the earth or from the sun. Frankly admitting, however, that both the time and place of the origin of life is a matter of pure speculation, in which we have as yet no observations or uniformitarian reasoning to guide us, Osborn advances five hypotheses in regard to it as follows:

An early step in the organization of living matter was the assemblage of several of the chemical elements essential to life. Of these the four most important elements were obtained from their previous combination in water, from the nitrogen compounds of volcanic emanations or from the atmosphere, consisting largely of nitrogen, and from atmospheric carbon dioxide. The remaining elements came from the earth.

Whether or no there was a sudden or a more or less serial grouping of these elements, one by one, Osborn is led to a second hypothesis that "they were gradually bound by a new form of mutual attraction, whereby the actions and reactions of a group of life elements established a new form of unity in the cosmos, an organic unity or organism quite distinct from the larger and smaller aggregations of inorganic matter previously held or brought together by the forces of gravity."

This leads to the hypothesis that since all living cells are colloidal the grouping of the "life elements" took place in a

state of colloidal suspension, for it is in this state that the life elements best display their incessant action, reaction and interaction.

With this assemblage, mutual attraction, and colloidal condition, a fourth hypothesis is that there arose the rudiments of competition and selection. "Was there any stage in this grouping, assemblage, and organization of life forms, however remote or rudimentary, when the law of natural selection did not operate between different unit aggregations of matter? Probably not, because each of the chemical life elements possesses its peculiar properties which in living compounds best serve certain functions. This coöperation was also an application of energy new to the cosmos." In other words, every "life element" has its single and multiple services to render to the organism.

And as a fifth hypothesis relating to the origin of organisms, Osborn advances the idea that the evolution and specialization of various enzymes has proceeded step by step with the evolution of plant and animal functions, "since in the evolution from the single-celled to the many-celled forms of life and the multiplication of these cells into hundreds of millions, into billions, and into trillions, as in the larger plants and animals, biochemical coördination and correlation become increasingly essential."20

Conclusion. Such are the principal attempts of modern biologists to formulate in some concrete way the evolution of matter in the living state from the elements of the earth. Their consideration is valuable in that it indicates the uniformitarian trend which, at the present day, biological thought follows in this field, and also the diversity of results arrived at by the scientific imagination when it is largely untrammeled

20 Osborn, H. F., "The Origin and Evolution of Life upon the Earth." Scientific Monthly, vol. 3, 1916, pp. 5-22, 170-190, 289-307, 313-334, 502-513, 601-614.

by facts.

One, however, cannot but admire the scientific

caution of Huxley when he said:

"Looking back through the prodigious vista of the past, I find no record of the commencement of life, and therefore I am devoid of any means of forming a definite conclusion as to the conditions of its appearance. Belief, in the scientific sense of the word, is a serious matter, and needs strong foundations. To say, therefore, in the admitted absence of evidence, that I have any belief as to the mode in which existing forms of life have originated, would be using words in a wrong sense. But expectation is permissible where belief is not; and if it were given to me to look beyond the abyss of geologically recorded time to the still more remote period when the earth was passing through physical and chemical conditions, which it can no more see again than a man can recall his infancy, I should expect to be a witness of the evolution of living protoplasm from not living matter. I should expect to see it appear under forms of great simplicity, endowed, like existing fungi, with the power of determining the formation of new protoplasm from such matters as ammonium carbonates, oxalates and tartrates, alkaline and earthy phosphates, and water, without the aid of light. That is the expectation to which analogical reasoning leads me; but I beg you once more to recollect that I have no right to call my opinion anything but an act of philosophical faith."21

Thus since biologists are at the present time absolutely unable, and probably will be for all time unable, to obtain empirical evidence on any of the crucial questions relating to the origin of life on the earth, their endeavors are and must be directed chiefly toward an intensive analysis of life manifestations as exhibited in the physical basis of individual

21 Huxley, T. H., "Biogenesis and Abiogenesis." Presidential address, Brit. Assoc. Adv. Sci., 1870. "Collected Essays," vol. 8.

organisms, in their bionomic relations, and in the kaleidoscopic panorama which geological history presents of their evolution. In the closing words of Darwin's Origin of Species:

"It is interesting to contemplate a tangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent upon each other in so complex a manner, have all been produced by laws acting around us. . . . There is grandeur in this view of life with its several powers, having been originally breathed by the Creator into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being evolved."

CHAPTER IV

THE PULSE OF LIFE

RICHARD SWANN LULL

PROFESSOR OF VERTEBRATE PALEONTOLOGY IN YALE UNIVERSITY

THE stream of life flows so slowly that the imagination fails to grasp the immensity of time required for its passage, but like many another stream, it pulses as it flows. There are times of quickening, the expression points of evolution, and these are found to be coincident with geologic change. These coincidences are so frequent and so exact that the laws of chance may not be invoked to account for them. They stand to each other in the relation of cause and effect.

This does not imply the acceptance of any one philosophical factor of evolution, for whether the creature is directly modified by environmental change, or indirectly through induced habit, or whether nature merely sets a standard to which the organism must attain if it would survive, matters not; the fact remains that changing environmental conditions stimulate the sluggish evolutionary stream to quickened movement. Whenever it has been possible to connect cause and effect, the immediate influence is found to be generally one of climate, back of which lies, as the main cause, earth shrinkage and a consequent warping of the crust, with the elevation and spread of the lands and the formation of mountain ranges. In addition to this mundane cause, there are the complex rhythms in solar energy and the consequent variation in the amount of solar-derived heat. For example, the most generally accepted