THE MUTATION HYPOTHESIS 71 



with the greatest caution. Reference has already been made 

 to the difficulty of observing small differences between indi- 

 viduals of the same race among animals and plants. It is 

 quite obvious that all the special characters of the domesti- 

 cated races have been produced by the intervention of man. 

 Man, however, has generally been capable of selecting only 

 considerable differences, that is, differences which are larger 

 than usual. He has always selected animals or plants which 

 vary from the mean of the race more than did their fellows. 

 Whatever else he has selected, then, he has always selected 

 variability, which is just as much a character as anything 

 else. We should therefore naturally expect the larger 

 variations to be much more frequent among domesticated 

 animals and plants than among wild races. This coincides 

 exactly with the experience of de Vries, although not with 

 his conclusions. Among about a hundred wild indigenous 

 plants in Holland, he found that no considerable varia- 

 tions occurred. When, however, he dealt with (Enothera 

 lamarckiana, he found many large variations. It has 

 already been shown that (E. lamarckiana is not known as 

 a wild species, that it is not indigenous to Holland, that 

 it has been subjected to artificial selection for considerably 

 over a hundred years, and is probably a hybrid. We have 

 seen also, in the cases where large variations are common 

 among wild animals, that these are not perpetuated as 

 a rule. 1 



G. A. Boulanger, after describing his breeding experi- 

 ments with (E. lamarckiana, writes as follows: "To sum 

 up, I would suggest the possibility of the mutations-theorie 

 being based on false premises. De Vries has assumed, 

 without any justification, that (Enothera lamarckiana is 

 a natural species. The fact that it was originally described 

 from a garden fiower, grown in the Paris Jardin des Plantes, 

 and that, in spite of diligent search, it has not been dis- 

 covered wild anywhere in America, favours the probability 

 that it was produced by crossing various forms of the poly- 



1 See p. 65. 



