86 EVIDENCES AND LIMITATIONS 



artificial breeding appear to be numerous and signifi- 

 cant.^ But their number and value is much reduced 

 by the doubts which are felt as to the independence 

 and permanence of the species which are said to be 

 originated by such means. Moreover it has to be 

 remembered that many of the mutations which are 

 attributed to domestication have been too ancient to 

 come within scientific observation. They cannot, 

 therefore, be employed as direct evidence. The only 

 instances, if any, that can thus be used, are the varieties 

 which modern breeders have produced by careful selec- 

 tion and cross-breeding. Whether any of these vari- 

 eties constitute independent species is still a debatable 

 question; and the fact that artificially produced vari- 

 eties show a tendency to revert to type when aban- 

 doned to the conditions of pure nature has to be faced. 

 These limitations, however, do not deprive the phe- 

 nomena of artificial selection of value as indirect evi- 

 dence of natural evolution. If it is not possible to 

 assert without fear of contradiction that the breeder 

 can produce new species, it is at least certain that his 

 new varieties appear like species in the making — 

 varieties which will become fixed, independent, and 

 permanent species when their culture has been con- 

 tinued long enough. The forces and laws which 

 account for the possibilities of domestic culture are, of 

 course, natural ones, for men cannot change such forces 

 and laws, but can only manipulate them and facilitate 

 their working. If, therefore, the breeder seems to be 



^ On this subject, see Darwin, op. cit., chh. i, ii. 



