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LECTURE IV.

ORGANIZED EXISTENCE: LIFE AND ITS DEVELOPMENT.—(DARWIN'S "THEORY OF EVOLUTION.")

TN prosecuting our inquiry as to the most recent advances in science, we pass now from inorganic to organic existence; from the testimony of physicists, to that of zoologists. This transition in itself starts a scientific problem, beyond which we are carried onward to a distinct and very complicated area of existence, higher in order, and pressing upon attention an incalculable variety of details, exceedingly difficult to harmonize. In the earlier stage of physical research, all observation and experiment lead forward to general results, which gain ready acceptance because they may be said to be involved in scientific procedure itself. In this more advanced stage it is otherwise. In the former, unorganized matter is the same everywhere; and the laws of energy can be studied with equal facility in Europe or in America, in northern latitudes or in southern. But when we begin to direct attention upon life in its manifold forms, as these are scattered all over the world, multitudes of distinct observations have to be prosecuted, and their results slowly accumulated, before even the most competent workers can occupy a position from which it is possible to make a beginning with our forecast of general conclusions. Even in the most favorable circumstances, a great deal must be left to problematic inference, and even to imagination. Gatherings of facts may be recorded in a manner which places them beyond reach of doubt, while theories founded upon them hang long in suspense, waiting confirmation on condition of being able to endure protracted criticism, and manifold applications. This accounts for the difficulty experienced in finding ready to hand general conclusions which have secured universal acceptance, when we begin to move somewhat freely over the wide regions presenting the manifold problems of organized existence. And as it is solely with general conclusions, that religious thought is concerned, some share of perplexity must attach to the attempt to discuss the question of harmony. We must here therefore be considerably involved in questions affecting theories which have gained wide favor in scientific circles, as well as with clearly recorded and certain results. Some general questions, such as that affecting the classification of animals, must be regarded as peculiarly scientific. Whether the classification of Linnaeus, or of Cuvier, or some other more recently suggested, is to be preferred, is a matter which does not here concern us. But a theory of the origin of species must be considered, because it is not purely scientific, but brings science into direct relation with common thought as to the order of the universe, and may therefore stand related to religious thought.

Immediately on directing attention to organized existence,—to Life in any form,—we encounter a new problem, namely the relation of the organized to the unorganized. How is the appearance of this higher order of existence to be accounted for? Can we find in the nature of matter, and in the mechanical and chemical laws influencing its position and combination, any explanation of the appearance of life in the world? Or must we regard life as a new and higher fact, unexplained by reference to the lower form of existence, and incapable of explanation in this way? Whether there is a clear line of demarcation between vegetable and animal life is a comparatively subordinate question. It is the wider and more perplexing question which most fundamentally affects our general conceptions as to the history and government of the world? And when this question is pressed singly,—how can we account for the appearance of life in the world ?—science has no answer to present. Life still remains a mystery in scientific times, as it had been in past ages. Much has been written as to the origin of species; nothing to any purpose has yet been said as to the origin of life itself. The secrets of the universe in this respect have eluded discovery, and a constrained silence is the consequence.

But if science itself has nothing to say as to this fundamental problem, scientific men have much to say as to the probability of a true solution of the mystery being forthcoming. There is in many quarters an expectation that we may yet understand the physical principles, that is, the mechanical and chemical combinations, which go to explain life as a working organism.* The suggestions of Rumford and Joule may yet bear results in this direction, for it is matter of general agreement that living organism may be regarded as an engine doing a given amount of work, on condition of being supplied with a given amount of fuel in the form of nourishment. When therefore Rumford suggests that the animal is a more economical engine than any of the mechanical contrivances which man constructs, and when Joule advances considerably beyond this to suggest that the animal more resembles an electro-magnetic engine, than a heat engine, it seems quite within the range of possibility that in some such direction discovery may yet be made of the physical principles involved in life.

This, however, leaves untouched the deeper question as to the origin of life. We are entirely ignorant of any beginning of life which is not traced directly to a preceding living organism. Either, as in the case of plants, there is increase of life by fission, or separation from an earlier growth, or by means of seed grown upon the parent plant; or, as in the case of animals, by germ or ovum. But the

* Tait's Recent Advanees, p. 23.

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