Page:The New International Encyclopædia 1st ed. v. 03.djvu/108

BIOLOGY. future, as they do now. While it is true that natural seloction does not make anything,, it does take awav all sijniificanee from the reasons some thinkers once thought they had for believino; that a living being is anything else than a natural body with a natural' history. No two objects, living or dead, ever are exactly alike; and if we admit the endless diversity of nature, and the struggle for existence, natural selection is a fact. WhiTe we find it hard to discover any difference between individual house-llics. or ants, or bees, they no doubt differ among themselves in many ways: some excelling in the duration and rapid- ity" of their ffight. while others fall below the average in size of wings, or strength of muscles, or in general coordination for flight. The in- sects that inhabit wind-swept islands are in con- stant danger of destruction at sea. and those that flv most are most in danger, while those that, for anv reason, fly little or not at all are safest, and live longest," and have most descendants. Kerguelen Island is said to be one of the stormi- est places on the globe. There are no trees or bushes to afford shelter on the island, which is swept by almost perpetual gales. It is inhabited by several flies, by numerous beetles, and by a moth, but all are' incapable of flight, and most are entirely without wings. It is often said that they have" lost their wings in order to escape daiiser. but this is only a figure of speech. Ae need not know who or what has made them deficient in order to understand the facts. All that did fly have been exterminated, and there would not be any survivors if some had not been deficient in ability or in inclination to fly.

The Ttieory of ExPERiENrE.!Most of the modern critics of natural selection contend that the raw material of which it is said to stand in need is supplied by that influence of the condi- tions of life which we are accustomed to sum up imder the general word 'experience.' They attribute to individiial or to ancestral experi- ence the origin of the adajitive actions which natural selection picks out and preserves. Our own times, like the two preceding centuries, are not.able for the prevalence of experience phi- losophv": vet there has been little reflective or philosophical study of experience in the light of modern biolog>'." although it is clear that the biologist who a.sserts that experience furnishes the raw material which natural selection picks out and preserves must be preimred to give an account of experience which does not attribute it to natural selection.

Recent experiments show that when an animal is placed in such circumstances that it c.-in, by some simple action which is well within the com- mand of its organization, obtain some object that it likes, the way in which it acquires facil- ity in accomplishing the desired action is very noteworthy, and strikingly the same in all the animals that have been studied. A monkey, for example, before which is placed a box ihat contains, in full view but out of reach, some attractive article of food, which can be obtained only by some simple but definite action, such as pulling a string, or lifting a latch, or pulling out a peg. shows no capa- city for learning to perform this action through seeing it done, or by being shown how to do it. If, however, any oiie among the indefinite and uncoordinated and aimless movemnits which it makes in trying to reach the object happens to be the proper one and to succeed, and if the time which has been consumed in irrelevant movements be noted, it is found that the adap- tive movement comes a little sooner al the sec- ond trial, and that, as the experiment is repeat- ed day after day. the interval between the be- ginning of effort and success grows shorter and shorter, until at last, in course of time. Ilie monkey 'acquires' the art of lifting the latch or of pulling the string without any preceding misdirected movements. He has "learned by experience' to perform the responsive action un- der the stimulus of its sensible perception, and thus to gain the desired end: but his experience has come aboiit through the gradual extinction of the aimless and misdirected movements, and the survival of those that are definite and exact. Experiments with fishes and tiu'tles and other animals give the same result. They learn by experience, but their experience consists in the survival of the fittest activities and the inhibi- tion of those that are unsuccessful.

The eyes of the human infant move independ- ently and aimlessly, and it is only after it has spent weeks in ex[)crimenting that it suppresses tile vague and indefinite movements, and thus gradually and slowly acquires the useful art of coordinating compensating nniscles in such a way as to move both eyes together so as to see ob- jects single and solid. Instead of flat and tremu- lous.

Herbert Spencer has pointed out the way in which opinion as to the limits and scope of the powers of governments over the governed has undergone slow modification with the progress of civilization until most of the extraneous and irrelevant notions of earlier and more primitive peoples have been stripped ofi'. leaving only that hich is essential to survive and come down to modern times.

"All science," says Huxley, "starts with hy- potheses — in other words, with assumptions that are unprovedf Ahile they may be, and often are, erroneous: but which are better than nothing to the seeker after order in the maze of phe- nomena. And the historical progress of every science depends up(m the criticism of hypotheses 7— on the gradual stripping ofl', that is, of their untrue or superficial parts — until there remains only that exact verbal expression of as much as we know of the fact, and no more, which constitutes a perfect scientific theory."

It surely requires only a comprehensive view of these examples of 'experience.' drawn from the most widely separated types of vital activity, to see that they all consist in the extinction of the aberrant and the misdirected and the uncoordinated, until only that which is exact and definite survives. There is, therefore, much to urge in defense of Berkeley's contention that "the work of experience is to unravel our prejudices and mistakes, untwisting the closest connections, distinguishing things that are different, instc;id of corTfused and perplexed, giving U9 distinct views, gradually correcting our judgment and reducing it to a philosophical exactness." But the correction of vital activities, and their reduction to exactness by the extinction of those that are confused and pcrpk'xed, and the survival of those that are definite and distinct, is what we mean by natural selection.