THE EVOLUTION OF LIVING BEINGS. 55 



furnished by the Petunias with green-rimmed petals 

 which were obtained about 1830 in England, and again 

 in 1914 in my garden at Bennebroek, by crossing the 

 same Linneons as were crossed 80 years ago in Eng- 

 land, viz Petunia violacea and Petunia nyctaginiflora. 

 It is of course equally indifferent to the question of the 

 origin of species, whether there exist other kinds of 

 segregations than Mendelian ones or not; all that is 

 necessary, is that new homozygous combinations arise 

 finally from a cross. This can evidently even happen 

 without segregation, if two heterozygotes, containing 

 among their different gametes some identical ones, 

 mate, and two of these identical gametes form together 

 a zygote. 



New species consequently are the result of the mating 

 of identical gametes, derived, usually indirectly , from the 

 mating of two gametes of different constitution (by cros- 

 sing heterozygotes or homozygotes of different con- 

 stitution) or derived directly , from the cross of two hetero- 

 zygotes, having among their otherwise different gametes 

 some identical ones in common. 



