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Show 122 DARWINISM CHAP. that of Darwin or as supplementary to it. Before doing this, however it will be well briefly to summarise the facts and aro·umedts already set forth, because it is only by a clear co~1prehension of these that the full impor~ance of the theory can be appreciated and its further app~ICatwns understood. The theory itself is exceedingly simple, ~nd. ~he facts on which it rests-though excessively numerous mdividually, and coextensive with the entire organic world-yet come under :t few simple and easily understo.od classe.s. These !acts are,first, the enormous powers of mcrcase m geometncal progression possessed by all organisms, and the inevitable struggle for existence among them; and, in the second place, the occurrence of much individual variation combined with the hereditary transmission of such variations. From these two grea.t classes of facts, which are univcr.,al and indisputable, there necessarily arises, as Darwin termed it, the "preservation of favoured races in the struggle for life," the continuous action of which, under the ever-changing conditions both of the inorganic and organic universe, necessarily leads to the formation or development of new species. But, although this general statement is complete and indisputable, yet to see its applications under all the complex conditions that actually occur in nature, it is necessary always to bear in mind the tremendous power and universality of the agencies at work. We must never for an instant lose sight of the fact of the enormously rapid increase of all organisms, which has been illustrated by actual cases, given in our second chapter, no less than by calculations of the results of. unchecked increase for a few years. Then, never forgctJting that the animal and plant population of any country is, on the whole, stationary, we must be always trying to rcalis~ the ever-recurring destruction of the enormous annual increase, and asking ourselves what determines, in each individual case, the death of the many, the survival of the few. We must think over all the causes of destruction to each organism,-to the seed, the young shoot, the growing plant, the full-grown tr~e, or shrub, or herb, and again the fruit and seed ; and among ammals, to the egg or new-born young, to the youthful, and to the adults. Then, we must always bear in mind that what goes on in the case of the individual or family group we may v NATURAL SELECTION 123 observe or think of, goes on also among the millions and scores of millions of individuals which are comprised in almost every species ; and mu?t get rid. of ~he idea that chan?e determines which shall hve and whiCh dw. For, a,lthough m many individual cases death may. be ~ue to chance rather than to any inferiority in those whiCh d10 first, yet we cannot possibly believe that this can be the c~se on the large sc~le on which nature works. A plant, for mstance, cannot be mcreased unless there are suitable vacant places its seeds can grow in, or stations where it can overcome other le s :Vigor~us and healthy plants. The seeds of all plants, by th01r vaned modes of dispersal, may be said to be seeking. out such places in which to grow; and we cannot doubt that, m the long run, those individuals whose seeds are the mo t numerous, have the greatest powers of dispersa,l, and the gr?at?s~ vigour of growth, will leave more descendants than the md1v1duals of the same species which are inferior in all these respects, although now and then some seed of an inferior individual may chance to be carried to a spot where it can grow and survive. The same rule will apply to every period of life and to every da~ger to which plants or animals arc exposed. The best orgamsed, or the most healthy, or the most active, or the best protcct~d, or tho most intelligent, will inevitably, in the long run, ga~J~ an advantage over those which are inferi~r i~ those qual_Itic ·; that is, the fittest will s~trvive, the fittest bcmg, I~ each p~r~ICular case those which are superior in the special quahtws on whi~h safety depends. At one period of life, or to escape one l<:ind of danO'er concealment may be necessary; at another time, to escabp e ' another danger, swiftness ; at anot h er, I.. ntc l - ligence or cunning; at another, the power to endure r~m ~r cold or hunO'cr · and those which possess all these facultws Ill b ) 0 the fullest perfection will generally su~'vive. . Having fully grasped thccic facts m all th01r fulness ~11<l in their endless and complex result , we have next to con 'Iller the phenomena of variation, discussed in the third. and fonr~h chapters; and it is here that perhaps the greatest d.lfficulty w1ll be felt in appreciating the full importance of th~ evidence as set forth. It has been so generally the practiC~ to speak of variation as something exceptional and comparativcl!'. rare-as an abnormal deviation from tho uniformity and stab1hty of the |
