568 Mutations 



great is the chance for a single individual to be 

 destroyed in the struggle for life! Hundreds 

 of thousands of seeds are produced by La- 

 marckiana annually in the field, and only 

 some slow increase of the number of specimens 

 can be observed. Many seeds do not find the 

 proper circumstances for germination, or the 

 young seedlings are destroyed by lack of water, 

 of air, or of space. Thousands of them are so 

 crowded when becoming rosettes that only a few 

 succeed in producing stems. Any weakness 

 would have destroyed them. As a matter of 

 fact they are much oftener seen in cultures 

 than in the field with the usual unfavorable con- 

 ditions; the careful sowing of collected seeds 

 has given proof of this fact many times. 



The experimental proof of this frequency 

 seems to overcome many difficulties offered by 

 the current theories on the probable origin of 

 species at large. 



VI. The relation between mutability and fluc- 

 tuating variability has always been one of the 

 chief difficulties of the followers of Darwin. The 

 majority assumed that species arise by the slow 

 accumulation of slight fluctuating deviations, 

 and the mutations are only to be considered as 

 extreme fluctuations, obtained, in the main, by a 

 continuous selection of small differences in a 

 constant direction. 



