THE EVOLUTION OF LIVING BEINGS. 159 



The conclusion therefore is : crossing of allogamous 

 forms leads to the production of new forms, most of which 

 sooner or later fall into separate non-intercrossing groups, 

 each of which however consists of different intercrossing 

 forms. Such groups are called Linneons. 



Such Linneons can adapt themselves to changed cir- 

 cumstances by giving birth to new forms by crossing 

 the different types they contain. These new forms do 

 not transgress the limits of the Linneon and are gradually 

 also exterminated by the struggle for life, which ends in 

 the selection, either of a dominant hybrid type ill fitted to 

 give rise to new-forms, or of a recessive type entirely 

 unable to form new forms. 



Such Linneons consequently also, are gradually exter- 

 minated by the struggle for life, and here also the forms 

 within it, last exterminated, obtain the epitheton ornans : 

 selected ones. 



We can express this shortly by saying: 

 Linneons arise by crossing and are gradually extermi- 

 nated by the struggle for life, the last surviving ones ob- 

 taining the epitheton ornans: selected ones. 



All this is probably parallelled, en grand, in the appea- 

 rance and extinction of the great classes. A cross between 

 two greatly differing gametes gives rise to a great diversity 

 of new forms which we group into families, genera and 

 Linneons, to all of which applies what has been said 

 above of the Linneons: gradual dimunition of the oppor- 

 tunities of crossing and consequently of the birth of new 

 types, able to withstand changed conditions. This must 



