No. 549] ON DIFFERENTIAL MORTALITY 525 



The answer to (a) depends, as has been pointed out 

 above, upon the inheritance or non inheritance of tlie 

 variations in seed weight. This question can not lie (lis 

 cussed as yet, but from the data in hand, it scents to me 

 likely that this selective elimination has little or no evo- 

 lutionary significance. Certainly it is, as far as our ovi 

 dence goes, not a cause of progressive change hut only a 

 factor tending to preserve an established type. It would 

 then be an illustration of the "periodic selection" of 

 Pearson. 



The answer to (b) must he sought in the physiological, 

 and of course ultimately, in the chemical and physical 

 properties of the seeds of different weights. Experi- 

 ments directed to its solution are under way. 



Cold Spring Harbor, L. L, 

 July 15, 1902 



