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Show 62 STRUGGLE FOR EXISTENCE. [CH.A.P. III. in words the truth of the universal struggle for life, or In ore difficult-at least I have found it so-than constantly to bear this conclusion in mind. Yet unless it be thoroughly engrained in 'the mind, I am convinc~d ~hat. th~ w~ole economy of nature, with every fac~ on d~stributi~n, rarity, abundance, extinction, and variat1on, Will be dimly seen or quite misunderstood. We behold the face of nature briO'ht with gladness we often see superabundance of food · we do not see 'or we forget, that the birds which are idly singing round us most~y li~e on insects or seeds, and are thus constantly destroymg hfe ; or. we forget how largely these songsters, or their eggs, or thmr nesthngs, are destroyed by birds and beasts of prey; we do not always bear in mind that thouQ:h food may be now superabun-dant it is not ' so at all seLaJ sons of each recurri. ng year. I' should premise that I use th~ term Str~ggle .for Existence in a large and metaphoncal .sense,. Includ:ng dependence of one being on anot~er, and In?lu~I~g (which is Inore hnportant) not only the hfe o~ the ~ndivi~ual, ?ut success in leaving progeny. Two canine animals In a time of dearth may be truly said to struggle with each other which sh~ll get food and live. ~ut a ~lant on the edge of a desert is said to struggle for hfe. against the drought, though more properly it sh~uld be said to be dependent on the n1oisture. A plant which annually produces a thousand seeds of which on an average only one comes to maturity ;nay be more truly said to struggle with the plants of the same and other kinds which already clothe the ground. The misseltoe is de:pendent on the apple and a few other trees but can only In a far-fetched sense be said to struggle ~ith these trees, for if too many of the~e arasites grow on the same tree, it '~ill languish and dw. ~ut several seedling misseltoes, growing close together .on the same branch, may more trul:y b~ said .to struggle ~Ith each other. As the misseltoe Is disseminated by buds, its existence depends on birds ; and i~ may .metaphorically be said to struggle with other fru1t-b~anng: plan~s, in order to tempt birds to devour and thus dissemmate Its seeds rather than those of other plants. In these seyeral senses, which pass into each other, I us_e for convemence sake the general term of struggle for existence. CHAP. III.] HIGH RATE OF INCREASE. 63 A struggle for existence inevitably follows from the high rate at which all organic beings tend to increase. Every being, which during its natural lifetime produces several eggs or seeds, must suffer destruction during some period of its life, and during some se~son or occasional year, otherwise, on the principle of geometrical increase, its numbers would quickly becon1e so inordinately great that no country could support the product. l-Ienee as more individuals are produced than can possibly survive, there must in every case be a struggle for existence, either one individual with another of the same species, or with the individuals of distinct species, or with the physical conditions of life. It is the doctrine of Malthus applied with manifold force to the whole anhnal and vegetable kingdoms; for in this case there can be no artificial increase of food, and no prudential restraint fr01n marriage. Although some species may be now increasing, more or less rapidly, in numbers, all cannot do so, for the world would not hold them. There is no exception to the rule that every organic being naturally increases at so high a rate, that if not destroyed, the earth would soon be covered by the progeny of a single pair. Even slow-breeding man has doubled in twenty-five years, and at this rate, in a few thousand years, there would literally not be standing room for his progeny. Linnreus has calculated that if an annual plant produced only two seeds-and there is no plant so unproductive as this-and their seedlings next year produced two, and so on, then in twenty years there ·would be a million plants. The elephant is reckoned to be the slowest breeder of all known animals, and I have taken some pains to estimate its probable minimun1 rate of natural increase: it will be under the n1ark to assume that it breeds when thirty years old, and goes on breeding till ninety years old, bringing forth three pair of young in this interval ; if this be so, at the end of the fifth century there would be alive fifteen million elephants, descended from the first pair. But we have better evidence on this subject than mere theoretical calculations, namely, the numerous recorded cases of the astonishingly rapid increase of various animals in a state of nature, when circumstances have been |