92 THE EVOLUTION OF LIVING BEINGS. 



countries, causing them to be considered specifi- 

 cally" different. That this is so, is shown by Nilsson- 

 Ehle's experience that certain ,,species" of wheat, in- 

 troduced into Sweden, and cultivated there for some 

 time, become of quite another type by the weeding 

 out of the but little frostresistant strains by the 

 Swedish climate. 



In many cases, as we saw, freely intercrossing Jor- 

 danons cause the Linneons to get, in nature, a uni- 

 form aspect. 



Yet there are cases in which such Linneons show a 

 bewildering multiformity either in several or in one 

 respect, even at first sight. 



The most beautiful exemple of this, I ever saw, is fur- 

 nished by a series of about 200 specimens of Buteo 

 Buteo in the Leiden Museum, hardly two of which are 

 alike, and which resemble very much, what one would 

 expect to obtain, after segregation in F 2 a ). 



The reason, that this lot resembles an F 2 generation 

 probably is that here no selection has been at work, 

 because this bird of prey is so strong that it has 

 practically no ennemies in the regions in which it occurs. 



In cases, where the Linneon is more uniform in as- 

 pect but yet shows great diversity in one respect, the 

 explanation probably is, that as far as the variable" 

 character is concerned, selection did not take place. 



So f. i. Symphytum officinale which, at least in the 

 neighbour hood of Bennebroek is self-sterile and con- 

 sequently forms an intercrossing community, like that 



a ) I regret it greatly that it is not possible to publish a colored plate 

 of this most important series. 



