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subtle or manifest, characterise every individual thing in 

 creation ; so that it may safely be affirmed that there are 

 no two living beings, from the monad to the man, which, 

 however alike apparently, would not, if brought together 

 and compared, be found to differ, not only in one, but in 

 many respects — i.e. would betray variation. 



The tendency of Nature is, by the free intercourse 

 among the various individuals of a species, to check the 

 growth of any type of variation in special directions, and 

 so to maintain a fair level of uniformity ; if, however, a 

 change of the conditions of existence be brought about, 

 then any variations which help existence under the 

 altered conditions will manifestly be fostered, and tend to 

 accumulate, because the individuals so favoured have a 

 better chance of longer life and more numerous offspring. 

 For instance — in order to keep to our subject — if a number 

 of Ferns be transported to a warmer or colder climate than 

 is natural to them, in the first place, only those survive 

 which are best fitted to stand the change, and in the 

 succeeding generations, all those of their offspring whose 

 constitutions vary ever so little in the right direction will 

 grow stronger, scatter more spores, and transmit their 

 greater strength continually, until, in course of time, the 

 balance will be restored, and a tribe of Ferns of a different 

 constitution, and, what is more to the point, of distinctly 

 different appearance, will be found to exist. 



This is Nature's general method, which is a slow and 

 mercilessly extravagant one. But if we bring man upon 

 the scene, with his selective and protective power, the 

 process is enormously accelerated ; and, practically, ne 

 can do as much in the way of re-modelling a cow, a dog, a 

 pigeon, a flower, or even a Fern, in his own lifetime, as 

 Nature, left alone, would accomplish in thousands of years. 

 This re-modelling is effected by ihe constant selection by 

 the breeder, or horticulturist, or Fern-lover, of the types 

 nearest to his ideal one, and the rejection of all others, the 



