THE EVOLUTION OF LIVING BEINGS. I? 



the degree of visible difference was sufficient to make 

 out without experiment, whether it was inheritable 

 or not, in other words that an experienced systema- 

 tist could distinguish at sight whether two or more 

 individuals had the same constitution or not. 



This mistaken idea, the famous ,,systematischer 

 Blick", unfortunately reigns yet supreme in many her- 

 baria and musea of the present time. It has been ex- 

 posed to ridicule already in 1855 by JORDAN, who said: 

 t ,0n s'est efforci de mettre en vogue une theorie, qui 

 consiste dans Tadmission parmi les vegetaux de types 

 ,,specifiques tranches et dans 1'hypothese de la varia- 

 ,,bilite de ces memes types. 



This hypothesis, as Jordan so justly calls it, the 

 hypothesis of the variability of the species, has caused, 

 in my opinion, all the trouble we have experienced in 

 looking for the causes of the origin of species because 

 it withdrew from systematics as well as from all theories 

 of evolution every firm footing. 



Very rightly again Jordan has said: 



Rejeter le criterium de la permanence hereditaire, 

 c'est tout reduire a de simples hypotheses, a 1'arbi- 

 traire, a la fantaisie des appreciations individuelles, 

 c'est en un mot donner pour fondement a la science, le 

 scepticisme : ce qui revient a la detruire. 



And the cause of these individual appreciations, 

 cause of this scepticism which refused to accept the 

 existence of clear-cut species and considered all species 

 to be variable, was in the beginning the total neglect 

 of all experiments (by the older botanists), subsequent- 

 ly the insufficient application of the experimental test 



