XXIV.] WHAT IS "running out!" 377 



out, therefore, is not necessarily deterioration, though 

 the two are commonly confounded ; it is simply 

 change, modification.* If we say that the Peach - 

 blow potato, for instance, has run out, we simply 

 mean that it has disappeared. It has broken up into 

 many forms, perhaps. We cannot say that it has 

 degenerated, for degeneracy is a relative term, and 

 a variety or an individual which is inferior for one 

 purpose may still be superior for some other ; and 

 it is probable that there are many different grades 

 or kinds of variations in the remnants of this va- 

 riety, some poor, some good. 



Again, running out does not mean that the life 

 of the variety is necessarily limited in duration. As 

 a matter of philosophy, we are undoubtedly safe in 

 assuming that the duration of any particular form of 

 life will be limited, for there is evidence that spe- 

 cies have become extinct. Yet, as a matter of prac- 

 tice, the limits of the genetic duration of species and 

 varieties in nature concern us little ; and, at any 

 rate, there is no reason to suppose that varieties 

 possess necessarily a different limitation from species. 

 The presumption is, however, as Asa Gray long ago 

 pointed out,t that the older the variety, that is, 

 the greater the number of its generations, the greater 

 must be its chances of permanence, because it has 

 become pronounced in its character and has proved 

 its capability to persist. But I propose to limit 

 the present discussion to the mere disappearance of 

 varietal characteristics, through which we lose sight 



*This distinction was clearly made in a recent paper upon tomatoes. — Bull, 

 xxi. Cornell Exp. Sta. 83, 1890. 



tN. Y. Tribune, Dec. 8, 1874. Reprinted in Silliman's Journal and Sargent's 

 Scientific Papers of Asa Gray. 



