THE MELTING-POT 91 



of the species around Amsterdam were in a non- 

 mutable state. It is possible, as Weismann 

 suggested in one of his first evolutionary essays 

 (1872), that in the life of species, periods of 

 constancy alternate with periods of changeful- 

 ness. The human historian has often made a 

 similar remark. 



" In the course of his wanderings around 

 Amsterdam, De Vries came across a deserted 

 potato-field at Hilversum a field of treasure for 

 him. For there he found his long-looked-for 

 mutable plant, an evening primrose (CEnothera 

 lamarkiana). Like its nearest relatives, CEno- 

 thera biennis and CEnothera muricata, which it 

 excels in size and beauty of flowers, it probably 

 came from America, where it is a native. It 

 had probably 'escaped' at Hilversum about 

 1875, and in the following ten years it had 

 spread in hundreds over the field. It had been 

 extremely prolific in its freedom ; but that was 

 not its chief interest. 



" Its chief interest was its changefulness. It 

 had, so to speak, frolicked in its freedom. 

 Almost all its organisms were varying as if 

 swayed by a restless tide of life. It showed 

 minute fluctuations from generation to genera- 

 tion ; it showed extraordinary freaks like fascia- 

 tion and pitcher- forming ; it showed hesitancy as 

 to how long it meant to live, for while the 

 majority were biennial, many were annual, and 



