TENDENCY OF SPECIES TO FORM VARIETIES. 7 



he was strongly inclined to do (in favor of Mr. Wallace), the memoir 

 wliich he had himself written on the same subject, and which, as before 

 stated, one of ns had perused in 1844, and the contents of which 

 we had both of us been privy to for many years. On representing this 

 to Mr. Darwin, he gave us permission to make what use we thought 

 proper of his memoir, &c. ; and in adopting our present course, of 

 presenting it to the Linnean Society, we have explained to him that we 

 are not solely considering the relative claims to priority of himself and 

 his friend, but the interests of science generally; for we feel it to be 

 desirable that views founded on a wide deduction from facts, and ma- 

 tured by years of reflection, should constitute at once a goal from 

 which others may start, and that, while the scientific world is waiting 

 for 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 honour to be yours very obediently, 



Charles Lyell. 



Jos. D. Hooker. 

 J. J. Bennett, Esq., 



Secretary of the Linnean Society. 



1. Extract from an unpublished Wor-k on Species, by C. Darwin, 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 Means of Selec- 

 tion; 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 re- 

 flection 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 occasional 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 inhabitants, 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 are eight pairs of birds, and that only four pairs of 

 ihem annually (including double hatches) rear only four young, and 

 that these go on rearing their young at the same rate, then at the end 



