EVOLUTION its progeny were preserved, would go on multi- plying until it covered the earth or filled the sea. Space is fixed and food limited, and the consequence is a universal conflict, the war of races ; and in the " struggle for existence " multitudes perish and comparatively few sur- vive. This survival is not a matter of chance. Mr. Darwin maintains that it is regulated by law, and that those only survive which are in some way best adapted to the conditions of life. The strongest, the fleetest, the most cunning, and the best adapted to the condi- tions will live and multiply, while the less fit will disappear. The introduction of European plants and animals into New Zealand affords an instructive example of how races encroach on each other's areas, the weaker being extir- pated by the stronger in the competition for existence. Dr. Hooker says: " The cow grass has taken possession of the roadsides; dock and water cress choke the rivers; the sow thistle is spread over all the country, growing luxuriantly up to 6,000 feet ; white clover in the mountain districts displaces the native grasses ; and the native (Maori) saying is : ' As the white man's rat has driven away the native rat, as the European fly drives away our own, and the clover kills our fern, so will the Maoris disappear before the white man him- self.' " Mr. Darwin in his works gives a great number of facts showing how apparently trifling variations give advantages to their possessors, which determine their survival and become perpetuated in the race. The principle of natural selection, or, as it is termed by Her- bert Spencer, the " survival of the fittest," is now generally recognized as a genuine agency or vera causa, and the opponents of develop- ment admit that it may give rise to varieties, although they deny that it is competent to produce the deeper diversities of species. The extent of its operation remains yet to be de- termined, but many naturalists agree with Prof. Helmholtz that Mr. Darwin has contrib- uted to science an " essentially new creative idea." Mr. Darwin, however, does not as- sume to be the discoverer of the principle of natural selection, and he points out that others before him have recognized the action of the. process, though without seeing its full significance. What he claims is to have first shown the efficacy of the principle in producing divergency of types under the laws of variation and heredity. But having discovered a new factor in organic development, and published his work on the " Origin of Species " at the fortunate moment when naturalists had be- come widely dissatisfied with the old views, he became prominently identified with the devel- opment doctrine, and this has led many into the error of regarding Darwinism as the equiva- lent of evolution, of which, as we are now to see, it is but a minor part. The advance of civilization in the historical period gave rise to the modern idea of progress, which was strengthened by the discoveries made early in the present century concerning the past course of terrestrial life. The process was crudely conceived, in the one case as the successive development of all living creatures in a graded and linear series, and in the other case as the continuous movement of humanity toward a state of final perfection. About the year 1850 Mr. Herbert Spencer entered upon the system- atic study of the subject. The problem was strictly a scientific one, and he had a wide and accurate preparation for it by a mastery of scientific knowledge which Mr. Mill has pro- nounced "encyclopaedic." Mr. Spencer was also remarkable for his power of analysis, his grasp of wide-reaching principles, and his in- dependence of opinion. The essence of pro- gress is change. Mr. Spencer asked what, then, are the laws of change by which it is effected? Complying with the Newtonian canon that the fewest causes possible are to be assumed in the explanation of phenomena, he took up the question as resolvable in terms of matter, motion, and force. Progress being a theory of the successive changes by which things are produced, his task was to ascertain the dynamical conditions or laws under which the forms of nature rise, continue, and disappear. The objects of nature coexist and are maintained in a certain order in space. Newton discov- ered that this is effected by the operation of a simple and universal law. The objects of na- ture undergo changes in time, emerging and vanishing, some quickly and others slowly : is there a universal law by which these changes also are governed ? This was the aim of the re- search. Mr. Spencer early found that the con- ception of progress which implies movement in one direction only is erroneous. There is no unbroken march of events ; breaks and regres- sions alternate with advancement, and de- scending as well as ascending changes have to be accounted for. He therefore rejected the term progress as having erroneous implica- tions, and adopted the term evolution, as more fully indicating the scope of the inquiry and better expressing the strictly scientific nature of his theory. The naturalist Von Baer had already attempted to define and generalize the changes of organic growth, and had formulated them as from the homogeneous germ state to the heterogeneous adult state by a process of differentiation. Mr. Spencer soon found that this formula gave but a very partial account of what takes place in organic development. The change was shown to be not only from uniformity to unlikeness, or a differencing of parts, but from the indefinite to the definite, from the incoherent to the coherent, producing the integration of parts, or increasing unity with increasing complexity. The conditions and course of changes in which organic evolu- tion consists being ascertained, the question arose as to their extent, and Mr. Spencer be- came convinced that the law of organic move- ment is not an isolated fact in nature, but u ,that the process of change gone through by
