No. 547] GENET1CAL STUDIES ON (EN OTHER A 427 



this hypothesis, if finally accepted, most of the 

 " mutants" of De Vries are likely to fall into the class of 

 variants due to the mixing of different germ-plasms. If 

 the word mutation, in the sense of De Vries, is to have 

 a meaning more precise than that of variant it must be 

 kept for the type of variation from homozygous stock. 



That germinal variations may occur in homozygous 

 material seems to the writer more than probable, and it 

 is possible that many small variations are of this type. 

 The trend of experimental investigation, however, dis- 

 tinctly indicates that large variations (ranking as salta- 

 tions) are rare if present at all in homozygous material, 

 and consequently can not be important factors in o manic 

 evolution. The variations considered by Darwin are 

 chiefly either the small variations in relatively homozy- 

 gous forms, or the large and small variations from heter- 

 ozygous stock. 



