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Page:Popular Science Monthly Volume 35.djvu/380

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THE POPULAR SCIENCE MONTHLY.

influence is fundamentally different from all the natural dangers to which sea-fishes are exposed, since it is modern or recent, and has, therefore, failed to be recognized and provided against during the evolution of these animals. In this sense man's influence is unnatural, while all other dangers are natural. The danger from man is not only modern, but also totally anomalous in the rapidity of its approach. It has not grown up gradually and imperceptibly, but has swept over the entire ocean with a speed which leaves no chance for the production of compensating adjustments by the slow process of selection. If it were to remain without change, or were to change very slowly, there can be no doubt that all the species which were not quickly destroyed would ultimately be brought into adjustment, and would from that time on be able to resist; but what animal can become adjusted to an enemy who is able, in less than a generation, to increase his power by such inventions as the steamboat, the electric light, and the dynamite bomb? To marine food-fishes man is a catastrophe, not a natural enemy, and the natural methods of maintaining the harmony between oceanic animals and the slow geologic changes of the ocean bottom are of no avail against him.

A study of the destructive forces of nature shows that man is peculiar in other all-essential particulars. It is a well-known fact that of all the marine animals which fall a prey to enemies, or become the victims of accidents and diseases, all but an infinitesimal percentage are destroyed during infancy or youth. As soon as the eggs of a fish are laid, the process of decimation begins, and it is initiated on a scale which would quickly sweep the species out of existence if it lasted long; but, fortunately, it does not, and each day in the life of a young fish brings with it an enormous increase in the chance for a long life.

During the early stages of development the young fish is totally defenseless, and at the mercy of enemies and accidents; and, although each pelagic fish lays enormous numbers of eggs, not a single one could escape if the embryonic period were long. Natural selection has been constantly acting for untold ages to shorten it, however, for in each generation those eggs which developed most rapidly have most frequently escaped destruction; and as the fishes which hatched from these precocious eggs have inherited a tendency to produce similar eggs, the embryonic life has gradually grown short, and most pelagic eggs now develop so rapidly that it is not unusual for them to hatch within twenty-four hours after they are fertilized. After they are hatched the transparency and activity of the little fishes add greatly to their safety, although each school of young fishes is constantly encompassed on all sides by a host of enemies. I have found, by watching for an hour from the end of a wharf a school of some eight