JDancin- Wallace Celebration. 91 



the appearance of Mr. Darwin's complete work, some of the 

 leading- results of his labours, as well as those of his able 

 correspondent, should together be laid before the public. 



We have the honour to be yours very obediently, 



CHARLES LYELL. 

 Jos. D. HOOKER. 



,]. ,7. Bennett, Esq., 



Secretary of tJie Linnean Society. 



I. Extract from an unpublished Work on Species, by C. DARWIN, 

 Esq., consisting of a portion of a Chapter entitled, " On 

 the Variation of Organic Beings in a state of Nature ; on 

 the Natural Cleans of Selection ; on the Comparison of 

 Domestic Races and true Species." 



De Candolle, in an eloquent passage, has declared that all 

 nature is at war, one organism with another, or with external 

 nature. Seeing the contented face of nature, this may at 

 first well be doubted : but reflection will inevitably prove it 

 to be true. The war, however, is not constant, but recurrent 

 in a slight degree at short periods, and more severely at oc- 

 casional more distant periods ; and hence its effects are easily 

 overlooked. It is the doctrine of Malthus applied in most 

 cases with tenfold force. As in every climate there are 

 seasons, for each of its inhabitant?, of greater and less 

 abundance, so all annually breed ; and the moral restraint 

 which in some small degree checks the increase of mankind 

 is entirely lost. Even slow-breeding mankind has doubled 

 in twenty-five years ; and if he could increase his food with 

 greater ease, he would double in less time. But for animals 

 without artificial means, the amount of food for each species 

 must, on an average, be constant, whereas the increase of all 

 organisms tends to be geometrical, and in a vast majority of 

 cases at an enormous ratio. Suppose in a certain spot there 

 ^ire eight pairs of birds, and that only four pairs of them 

 annually (including double hatches) rear only four young, 

 -and that these go on rearing their young at the same rate, 



