No. 495] CONSTANCY OF MUTANTS 



183 



may be originated, and one ought, under crossing, to 

 observe the effects in terms of dominant and recessive or 

 cloaked features. Such effects I have observed to occur 

 in flax as against flax wilt and in wheat as against P. 

 graminus. Mr. R, H. Biffin, of England, is reported as 

 indicating that this is true in the case of wheat when 

 crossed with eincorn as against yellow rust. 



Bateson, in an admirable article upon ''Facts Limit- 

 ing the Theory of Heredity," 12 would also seem to en- 

 roll himself as against any adaptative response to 

 changed conditions as able to account for the origin of 

 such facts as I have observed in my cultures of flax and 

 wheat. Thus we read: 



"Though the response to change of conditions may have been 

 direct, it must not be hastily concluded that the response is adaptive. 

 The appeal to direct responses so common in evolutionary discussions 

 of thirty years ago, was made to account for the complex adaptations 

 of organism to environment. It is the total want of any evidence 

 supporting that appeal which has driven most of us to disbelieve in 

 the reality of any such claims, and there is nothing in the new evi- 

 dence, I think, which should shake the attitude of resolute agnosti- 

 cism which we have thus been led to adopt." 



However, to explain such observations as those noted 

 by me in the flax and wheat cultures seems to demand 

 the assumption that additional elements of heritable char- 

 acter arise on account of causes demanding adaptive re- 

 sponse. No theory of quantitative subtractions of unit 

 characters already formed would seem to be adequate 

 to account for the observed acquired qualities of resist- 

 ance. It is probable that only the cytologists are in 

 position to produce direct proof or disproof of the 

 apparently necessary suppositions as to character modi- 

 fications. Certainly those among them who are experi- 

 mentally inclined may cut along the line indicated with 

 much hope of uncovering many high lights to breeders. 

 Even here, it may be expecting quite too much that pos- 

 sibly pure physiological qualities should be represented 

 by structural units. 



12 Science, November 15, page 649. 



