86 Selection Does Not Lead to Origin of Species. 



The experience of breeders stands in direct contra- 

 diction to both these hypotheses. 



Let us examine these statements separately. We may 

 consider the first under two headings according as the 

 period in question refers to the future or to the past; 

 that is whether we are concerned with explaining a form 

 already existing, or with predicting its possible changes. 



Let us begin with the past. These changes have 

 been the result of some looo years of domestication and 

 selection, says Wallace.^ And Darwin said, as a result 

 of a criticism of Hoffmann^ "Perhaps hundreds of gen- 

 erations of exposure are necessary.''^ And in another 

 place, '7 cannot doubt that during millions of generations 

 individuals of a species will be born zvith some slight 

 variation profitable to some part of its economy/'^ Again 

 Alphonse de Candolle^ speaking of acclimatization, 

 says in a similar strain : *'I1 f aut, parait-il, pour une modi- 

 fication permettant de supporter des degres plus intenses 

 de froid, des periodes beaucoup plus longues que 4 ou 

 5000 ans, ou des changements de forme et de duree."^ 

 Of more modern authors J. Costantin writes as fol- 

 lows : ''Mais si pendant 50, 100, 1000 ans Taction du 

 milieu se maintient toujours la meme, les caracteres 

 hereditaires qui evoluent lentement, se consolident, de- 

 viennent de plus en plus stables.'^ 



Numbers of similar passages will doubtless occur to 

 the reader, but if he examines them carefully he will 

 see that whilst, to Darwin, the long period of time meant 



^ Wallace, Darwinism, 2d ed., p. 89. 



'Life and Letters, III, p. 345. 



^ Ibid., II, p. 124. 



* Originc des plantes cidtivees, p. 371. 



' Costantin, Accomodation des plantes aux climafs froid et 

 chaud. Bull. Scicntif. de Giard, T. 31, 1897, p. 489. 



