THE EVOLUTION OF LIVING BEINGS. l6l 



newLiwieons, and must conclude by analogy to the way by 

 which new classes originated. 



I should like to finish this chapter by calling once 

 more attention to one of the chief modem mistakes, 

 which, according to my view, has been made in the in- 

 terpretation of evolutionary facts. This is : that one has 

 looked for the cause of the origin of the different types 

 within a Linneon exclusively within the limits of that 

 Linneon, and so has been led to conclude, in most cases, 

 that the most common wild form within that Linneon, 

 was the ancestral one. 



So Bateson says, after crossing differently constitu- 

 ted white flowered types of the Linneon, Lath5niis 

 odoratus: 



„When Fj was grown however, it was clear that here 

 was „a remarkable opportunity of studyng a reversion 

 „in colour, due to crossing, for these plants instead of 

 „being white were purple, Uke the wild Sicihan plant 

 „from which our cultivated sweet peas are descended." 



And in his presidential Australian address he says 

 about this same point: 



„In spite of repeated trials no one has yet succeeded 

 „in crossing the sweet Pea with other leguminous 

 „species. We know that early in its cultivated history 

 „it produced at least two marked varieties which I can 

 „only conceive as spontaneously arising, though no 

 „doubt, the profusion of forms we now have, was made 

 „by the crossing of those original varieties". 



Now why accept another origin e. g. spontaneously 

 arising for these two ..original" varieties than for those 

 arisen later? 



