THE EVOLUTION OF LIVING BEINGS. 93 



of Lepus or Buteo, shows all kinds of colors in its flo- 

 wers, f. i. dark- violet, light violet, different shades of red, 

 whites etc. 



The same is the case with the blue-eyed, grey-eyed, 

 brown eyed and black eyed human individuals. 



The explanation is probably that none of these co- 

 lors gives a special advantage in our region and conse- 

 quently there is no elimination. 



That, notwithstanding these differences, we continue 

 to consider such heterogenous groups as Linneons, is 

 because we abstract from differences, considered to be 

 unessential, such as color of flowers etc. and take so cal- 

 led essential characters as criteria as explained on p. 50. 



That other self-sterile forms behave just the same 

 among plants as among animals, e. g. tend to become 

 uniform by selection of certain characteristics, is pro- 

 ved by the behaviour of the strictly-self sterile Car- 

 damine pratensis inside of which Linneon no such stri- 

 king differences in the colors of the flowers occur. 



In other cases, in which we find great diversity of 

 form, as f . i. within the Linneon : Taraxacum vulgar e, the 

 cause is very different from that which causes diver- 

 sity in the case of Symphytum. 



Taraxacum vulgare is — with the exception of one 

 form in Japan — , notwithstanding the fact that its 

 flowers are perfect and produce quantities of pollen, 

 never fertilized, but reproduces itself apogamously; 

 consequently selection can have no other effect than 

 to decrease the number of different forms, just as in the 

 case of strict self-fertilizers. 



Other polymorphous Linneons, like some in the gene- 



