104 THE ORIGIN OF SPECIES 



enabled to breed. Their geometrical ratio of increase, the 

 result of which never fails to be surprising, simply ex- 

 plains their extraordinarily rapid increase and wide diffu- 

 sion in their new homes. 



In a state of nature almost every full-grown plant 

 annually produces seed, and among animals there are 

 very few which do not annually pair. Hence we may 

 confidently assert that all plants and animals are tending 

 to increase at a geometrical ratio — that all would rapidly 

 stock every station in which they could anyhow exist — 

 and that this geometrical tendency to increase must be 

 checked b^ destruction at some period of life. Our 

 familiarity with the larger domestic animals tends, I 

 think, to mislead us: we see no great destruction falling 

 on them, but we do not keep in mind that thousands are 

 annually slaughtered for food, and that in a state of 

 nature an equal number would have somehow to be 

 disposed of. 



The only difference between organisms which annually 

 produce eggs or seeds by the thousand, and those which 

 produce extremely few, is, that the slow-breeders would 

 require a few more years to people, under favorable con- i 

 ditions, a whole district, let it be ever so large. The 

 condor lays a couple of eggs and the ostrich a score, I 



and yet in the same country the condor may be the more 

 numerous of the two; the Fulmar petrel lays but one 

 egg, yet it is believed to be the most numerous bird in 

 the world. One fly deposits hundreds of eggs, and an- 

 other, like the hippobosca, a single one; but this differ- 

 ence does not determine how many individuals of the 

 two species can be supported in a district. A large 

 number of eggs is of some importance to those species 



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