PREFACE. 



As a Preface is in reality a Postscriptum, the author may be permitted 

 to open it by mentioning omissions. 



The chief sin of omission he committed, is evidently the insufficient 

 justice he did to the writings of Anton Kerner von Marilaun, who 

 was he wants to state this explicitly the first to recognize fully the 

 significance of crossing as the underlying cause of the origin of species. 



What else should a preface say? 



If the work is as condensed as the present one, it may perhaps suffise 

 to repeat what Linnaeus said to Haller: 



Si quos in me vidisti errores, Tu sapientior haec ignoscas .... Quos 

 plures apud me detegere potes, eo gratior ero, turn possum omnia 

 corrigere vivus; post mortem non licet emendare propria opuscula. 



By which however the author does not consider himself bound to 

 gratefulness for every kind of criticism. 



He is f . i. very little impressed by the kind of criticism which calls it 

 , Inconceivable" ,,verging on the absurd" etc., to believe that crossing 

 can ever have been the underlying cause of the origin of new species, 

 from authors who firmly believe that the origin of new species should be 

 ascribed to some kind of variability; because it seems to him ,,absurd" 

 that those who advocate the origin of new species from a single ances- 

 tral one, should reproach an author who defends such an origin from 

 two ancestral species, of stating an ..inconceivable" opinion. 



To save another kind of critics unnecessary trouble, the author is 

 fully prepared to admit unhesitatingly that his theory explains but part 

 of the problem of evolution, so that there is ample room for them to ta- 

 ke part in the exploration of this most interesting field of investigation; 

 but he may be permitted to remark that the rest, left unexplained by 

 theories based on variability, is not smaller than that left unexplained 

 by his theory. 



