464 Mutations 



is no real and intimate connection between these 

 two great conceptions. Darwin frequently 

 pointed out that a long period of time might be 

 needed for slow improvements, and was also a 

 condition for the occurrence of rare sports. In 

 any case those writers have been in error, ac- 

 cording to my opinion, who have refrained from 

 experimental work on the origin of species, on 

 account of this narrow interpretation of Dar- 

 win's views. The choice of the material is 

 quite another question, and obviously all de- 

 pends upon this choice. Promising instances 

 must be sought for, but as a rule the best way 

 is to test as many plants as possible. Many of 

 them may show nothing of interest, but some 

 might lead to the desired end. 



For to-day's lecture I have chosen an in- 

 stance, in which the grounds upon which the 

 choice was based are very evident. It is the 

 origin of the peloric toad-flax (Linaria vulgaris 

 peloria). 



The ground for this choice lies simply in the 

 fact that the peloric toad-flax is known to have 

 originated from the ordinary type at different 

 times and in different countries, under more or 

 less divergent conditions. It had arisen from 

 time to time, and hence I presumed that there 

 was a chance to see it arise again. If this 

 should happen under experimental circum- 



