where. More thin that, other mutating forms have been 

 discovered, and by the application of biometric methods 

 much that is important regarding the relative variability 

 of mutants and their parent stock has been determined. Be- 

 sides 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 accumu- 

 lated which helps to support the main conclusions. Im- 

 portant as all these advances are, the most brilliant result 

 is that obtained along the lines of the induction of muta- 

 tions. By the injection into the developing ovary of a 

 plant allied to Lamarck's evening primrose of 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 produce forms quite distinct from the parent 

 type and, what is essential, 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 bound an organism is 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 speculate, but it is permissible to 

 suggest that it is perhaps of the nature of the rearrange- 

 ment, 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 pro- 

 cess involved, it is possible to suggest various ways in 

 which it might have been brought about. 



The line of departure of mutants from the parent type 

 is not in any one direction, and the manner of variation 



26 



