Page:Popular Science Monthly Volume 11.djvu/616

598 simply as changes, must not be regarded as peculiar, and fundamentally unlike the changes of inorganic matter.

Vital changes cannot, however, be regarded as changes simply standing by themselves, for, if we overlook their adjustment to the accomplishment of a purpose, we omit their most essential characteristic.

In so far as the contraction of a muscle is simply a change, it is without doubt purely physical; but in the adjustment of this change to a relation between external changes, in its adaptation to a purpose, we have something which has no parallel except in living things, and perhaps some of man's contrivances, such as the automatic governor of the steam-engine. Living things are distinguished from those which have not life by their adjustment, and life consists in this adjustment. Small as this difference seems when stated abstractly, and unimportant as it appears to be when we contrast such an organism as an amœba, with its simple and almost mechanical power of retracting its pseudopodia upon irritation, and such a highly-complex and changeable inorganic being as the ocean, yet, considered not in itself but in its adjustment to external relations, this power in the amoeba separates it very widely from all inorganic forms of existence, and connects it with the highest manifestations of life; for the series of adjustments of which that of the amœba is one of the simplest may be traced almost without break up to the most rational actions of man. A vorticella contracts and folds down its circlet of cilia when touched, because there is a connection between violent contact and the presence of danger; and this recognition of a connection between the changes of the external world is knowledge of the order of Nature, and this, in its higher form, is experience, and experience implies memory, and memory and experience are forms of consciousness. Thus we are able to understand the meaning of such expressions as that of Haeckel, that living things are distinguished from the not living by the possession of memory. It seems best to restrict the use of such purely subjective terms as memory and experience to the higher forms of conscious life, but we must not overlook the fact that the existence of an adjustment between internal and external relations implies something fundamentally like the memory of higher animals.

Finally, I wish to call attention to the fact that natural selection is constantly acting through the law of the survival of the fittest, in such a way as to bring each organism into more and more perfect harmony with its environment; that is, it is constantly bringing about a more and more exact, definite, and perfect adjustment between external and internal relations. If this adjustment constitutes vitality, and if natural selection furnishes an explanation of the manner in which the adjustment has been brought about, have we not, in the law of natural selection, an explanation of the origin of life?—not of course of the origin of the matter of life, nor of the changes of