No. 443-] 



MUTA TION IN PLANT! 



743 



to the parent type, and their constancy or fixity might not be 

 increased by artificial selection. 



7. Moretlai tit light >e simultaneously from 

 the parent individuals. 



8. Any one of the several mutants observed might originate 

 from several parent individuals simultaneously. 



9. The mutant forms- might arise from successive genera- 

 tions of the parent types. 



10. The mutant forms might in turn give rise to new types 

 after their separation from the parent type. 



The above statements rest directly upon observations of care- 

 fully conducted experimental cultures and admit of but little 

 argument as to interpretation. With this positive evidence at 

 hand questions at once arise as to the frequency, occurrence, 

 prevalence, exclusiveness, and as to the mechanism of discon- 

 tinuous variation as a method of origin of new species. When 

 we take up these points we at once enter a field of speculation 

 in which it may be seen there is opportunity for unlimited 

 argument, and in which with the bias to which most of us are 

 subject as a result of our training and investigations, it is diffi- 

 cult to maintain a purely judicial attitude. It will be profitable 



