560 Mutations 



be chosen in order to get the new type in its pure 

 condition. Nothing of the kind, however, was 

 observed. All the oblong a-mutants were pure 

 oblongas. The pedigree shows hundreds of 

 them in the succeeding years, but no difference 

 was seen and no material for selection was af- 

 forded. All were as nearly equal as the in- 

 dividuals of old elementary species. 



II. New forms spring laterally from the 

 main stem. 



The current conception concerning the origin 

 of species assumes that species are slowly con- 

 verted into others. The conversion is assumed 

 to affect all the individuals in the same direction 

 and in the same degree. The whole group 

 changes its character, acquiring new attributes. 

 By inter-crossing they maintain a common line 

 of progress, one individual never being able to 

 proceed much ahead of the others. 



The birth of the new species necessarily 

 seemed to involve the death of the old one. This 

 last conclusion, however, is hard to understand. 

 It may be justifiable to assume that all the in- 

 dividuals of one locality are ordinarily inter- 

 crossed, and are moreover subjected to the same 

 external conditions. They might be supposed 

 to vary in the same direction if these conditions 

 were changed slowly. But this could of course 

 have no possible influence of the plants of the 



