38 DARWINIANA. 



even if his theory fails in the endeavor to explain the 

 origin or diversity of species. 



" Nothing is easier," says our author, " than to admit in 

 words the truth of the universal struggle for life, or more diffi- 

 cult — at least I have found it so — than constantly to hear this 

 conclusion in mind. Yet, unless it he thoroughly ingrained in 

 the mind, I am convinced that the whole economy of Nature, 

 with every fact on distrihution, rarity, abundance, extinction, 

 and variation, will be dimly seen or quite misunderstood. We 

 behold the face of Nature bright with gladness, we often see 

 superabundance of food ; we do not see, or we forget, that the 

 birds which are idly singing round us mostly live on insects or 

 seeds, and are thus constantly destroying life; or we forget how 

 largely these songsters, or their eggs, or their nestlings, are de- 

 stroyed by birds and beasts of prey; we do not always bear in 

 mind that, though food may be now superabundant, it is not so 

 at all seasons of each recurring year." — (p. 62.) 



" 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 tweuty-five years, and 

 at this rate, in a few thousand years, there would literally not 

 be standing-room for his progeny. Linnaeus 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 pro- 

 duced 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 minimum rate of natural increase ; it will 

 be under the mark to assume that it breeds when thirty years 

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

 three pairs 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 



