96 



whether the differences are of such quality that they must needs 

 be recognized as specific by taxonomists ; what is important is 

 that they are differences which do not intergrade one with another 

 and which are inheritable in the second, third, and subsequent 

 generations, and that no tendency to revert to the parent form is 

 to be observed. 



The results of de Vries have been verified by cultures in this 

 country of his own and of other stock, so that there can be no 

 question that this Lamarck's evening primrose behaves in its 

 manner of mutation the same here as elsewhere. More than that, 

 other mutating forms have been discovered, and by the applica- 

 tion of biometric methods much that is important regarding the 

 relative variability of mutants and their parent stock has been 

 determined. Besides the actual experimental work, the history 

 of Lamarck's evening primrose has been traced back for more 

 than a century and a mass of inferential data is being accumulated 

 which helps to support the main conclusions. Important as all 

 these advances are, the most brilliant result is that obtained along 

 the lines of the induction of mutations. By injecting into the 

 developing ovary of a plant allied to Lamarck's evening primrose 

 reagents which might produce a chemical or osmotic effect upon 

 the cell contents, MacDougal has actually succeeded in inducing 

 mutations. The seed grown from the stimulated plant may pro- 

 duce forms quite distinct from the parent type and, what is essen- 

 tial, the mutations thus induced are constant to the second and 

 third generations. That such a result can be obtained is simply 

 astounding when one considers how firmly an organism is bound 

 by its heredity. It would appear that a tremendous shock had been 

 given the plant at a critical period in its life history which has 

 enabled or forced it to break down some of the minor barriers 

 imposed by its hereditary tendencies and to erect new ones, which 

 circumscribe its offspring as the original ones did its parent. As 

 to the precise nature of this shock we can at present only specu- 

 late, but it is permissible to suggest that it is perhaps of the nature 

 of the rearrangement, in a chemical sense, of the protoplasm of 

 the cells of the sexual generation. As to the natural production 

 of mutants, given such a conception of the nature of the process 



