XII. 



DURATION AND ORIGINATION OF RACE AND SPECIES. — 

 IMPORT OF SEXUAL REPRODUCTION. 



I. 



Do Varieties wear out, or tend to wear out ? 



(New Tobk Teibitne, and Amerioan Jottknal of Science and tub Ark, 



February, 1ST5.) 



This question has been argued from time to time 

 for more than half a century, and is far from being 

 settled yet. Indeed, it is not to be settled either way 

 so easily as is sometimes thought. The result of a 

 prolonged and rather lively discussion of the topic 

 about forty years ago in England, in which Lindley 

 bore a leading part on the negative side, was, if we 

 rightly remember, that the nays had the best of the 

 argument. The deniers could fairly well explain away 

 the facts adduced by the other side, and evade the 

 force of the reasons then assigned to prove that varie- 

 ties were bound to die out in the course of time. But 

 if the case were fully re-argued now, it is by no means 

 certain that the nays would win it. The most they 

 could expect would be the Scotch verdict, "not 

 proven.-' And this not because much, if any, addi- 

 tional evidence of the actual wearing out of any vari- 



