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Show 60 STRUGGLE FOR EXISTENCE. [CHAP. III. CIIAPTER Ill. STRUGGLE FOR EXISTENCE. Bears on natural selection- The term used in a wide sense- Geometrical powers of increase-Rapid increase of naturalised animals and plants-Nature of the checks to increase-Competition universal-Efl'ects of climate-Protection from the number of individuals-Complex relations of all animals and plants throughout nature -Struggle for life most severe between individuals and varieties of tho same species ; often severe between species of the same genus-The relation of organism to organism the most important of all relations. BEFORE entering on the subject of this chapter, I must 1nake a few prelin1inary remarks, to show how the struggle for existence bears on Natural Selection.. It ~as ~een seen in the last chapter that amongst organic bmngs 1n a state of nature there is some individual variability; indeed I am not aware that this has ever been disputed. It is immaterial for us whether a multitude of doubtful forms be called species or sub-species or varieties; what rank for instance, the two or three hundred doubtful form~ of British plants are entitled to hold, if the existence of any well-n1arked varieties be admitted. But the mere existence of individual variability and of son1e few well-marked varieties, though necessary as the foundation for the work, helps us but little in understanding ~?W species arise in nature. How have all those exquisite adaptations of one part of the organisation to another part, and to the conditions of life, and of one distinct organic being to another being, been perfected ? We see these beautiful co-adaptations most plainly in the woodpecker and misseltoe; and only a little less plainly in the humblest parasite which clings to the hairs of a quadru~ed or feathers of a bird ; in the structure of the beetle :vhiC}l dives through the water ; in the plumed seed wluc~ IS wafted by the gentlest breeze ; in short, we see beautiful CHAP. III.] STRUGGLE FOR EXISTENCE. 61 adaptations everywhere and in every part of the organic world. Again, it may be asked, how is it that varieties which I have. called incipient species, become ultimately conver~ ed Into good and distinct species, which in most cases obv:Iol!sly differ from each other far more than do the van~tws of. the sam~ species? How do those groups of spemes,. whi~h constitute what are called distinct genera, and whiCh differ from each other more than do the species of the same genus, arise ? All these results, as we shall more fully see in.the next. chapter, _follow inevitably from the struggle for hfe.- Owing to this struggle for life any vari~tion! h?wev~r slight and from whatever cause' proceeding, If It be In any degree profitable to an individual of an:y species, in its ~nfinitely complex relations to othe~ orgarnc beings and to external natur~, will tend to the pre~ervati~n of tha.t individual, and will generally be inherited by Its offspring .. ~he offspring, also, will thus have a better chance of surviVIng, for, of the many individuals of any species wh~ch are periodically born, but a small number can survive. I have called this principle by which each slight variat~on, .if useful, is preserved: by the term of Natural Selection, In order to mark its relation to n1an's power of selection. We have seen that man by selection can certainly produce great results and can ad~pt orga~ic beings to his own uses, through the accumulation of slight but useful variations, given to him by the hand of Nature. But Natural Selection, as we shall hereafter see, is a power incessantly ready for action and is as immeasurably superior to man's feeble efforts, as the ·works of Nature are to those of Art. We will now discuss a little 1nore in detail the strucrgle for existence. In my future work this subject shalf be treated, as it well deserves, at Inuch greater iength. The elder De Candolle and Lyelle have largely and philosophically s~o~n that all organic beings are exposed to severe competition. In regard to plants, no one has treated this subject with more spirit and ability than W. Herbert J?ea~ of Manchester, evidentlY: th~ res"?-lt of his great horticultural knowledge. Nothing IS easier than to admit |