60 GEOMETRICAL RATIO OF INCREASE. 



thus disseminate its seeds. In these several senses, which 

 pass into each other, I use for convenience sake the gen- 

 eral term of Struggle for Existence. 



GEOMETRICAL EATIO OF INCREASE. 



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 season or occasional year, 

 otherwise, on the principle of geometrical increase, its 

 numbers would quickly become so inordinately great that 

 no country could support the product. Hence, as more 

 individuals are produced than can possibly survive, there 

 must in every case be a struggle for existence, either one in- 

 dividual with another of the same species, or with the 

 individuals of disMnct species, or with the physical con- 

 ditions of life. It is the doctrine of Malthus applied with 

 manifold force to the whole animal and vegetable king- 

 doms; for in this case there can be no artificial increase of 

 food, and no prudential restraint from marriage. Although 

 some species may be now increasing, more or less rapidly, 

 in numbers, all can not 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 less than a thousand 

 years, there would literally not be standing-room for his 

 progeny. Linngeus has calculated that if an annual plant 

 produced only two seeds — and there is no plant so unpro- 

 ductive 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 the slowest 

 breeder of all known animals, and I have taken some pains to 

 estimate its probable minimum rate of natural increase; it 

 will be safest to assume that it begins breeding when thirty 

 years old, and goes on breeding till ninety years old, 

 bringing forth six young in the interval, and surviving till 

 one hundred years old; if this be so, after a period of from 



