THE AMERICAN NATURALIST [Vol. XLIX 



quent works. The chief foundation for his views, in re- 

 gard to the instantaneous origin of species, is furnished 

 by the conduct of (Enothera lamarckiana in cultures. It 

 has been somewhat generally recognized that 0. lamarck- 

 iana, and more recently, other species of the genus as well, 

 constitute crucial evidence in regard to the validity of the 

 mutation hypothesis on the botanical side. A great many 

 investigations on the genetics and cytology of 0. lamarck- 

 iana and other species, as well as crosses between species 

 and 1 1 mutants" of (Enothera, have been carried on during 

 the past decade by De Vries, and his followers and oppo- 

 nents. As a result a huge and highly technical literature 

 has grown up. (Enothera is obviously regarded, on the 

 botanical side at any rate, as the touchstone of the muta- 

 tion hypothesis as formulated by De Vries. Obviously 

 if this genus does not stand the test of critical investiga- 

 tion, the mutation hypothesis, so far as its validity de- 

 pends upon De Vries 's chosen illustration, is discredited. 



Since (Enothera and by obvious implication the Ona- 

 graeeae, to which it belongs, have become authority for 

 the mutation hypothesis, in its latest revival, they must 

 like Caesar's wife be beyond suspicion. Like Caesar, 

 (Enothera has hirmtic a name of authority and its family 

 affairs accordingly, should be beyond suspicion, when sub- 

 jected to the most searching investigation. It is appar- 

 ently just in this direction that the weak spot of the muta- 

 tion hypothesis lies. Too much attention has apparently 

 been given to ringing the changes on the so-called mutants 

 of (Enothera and not enough to the investigation of 

 the general morphological situation in the Onagraceae, to 

 which this much-discussed genus belongs. 



Unusual variability in plants is ordinarily regarded as 

 prima facie evidence of hybridism and the suggestion has 

 in fact frequently been made by professional geneticists 

 (e. g., Bateson, Davis, East, Gates and others) that 

 (Enothera lamarckiana is a hybrid. It is perhaps of inter- 

 est in this connection to recall that one of the commonest 

 expedients adopted by the practical breeder, for breaking 



