THE AMERICAN NATURALIST 



[Vol. LI 



with nanella, nanella does not appear in Fj, and in Fj 

 appears in a fairly definite ratio in the progeny of the 

 suhrohusta forms thus produced (de Vries, 1913), whereas 

 the Lamar chiana forms produced breed true, after their 

 usual fashion. Obviously this behavior is simply a conse- 

 quence of the fact that ruhrinervis does not produce a 

 gametic series containing nanella, and, therefore, nanella 

 can not appear in F^. The impressively orderly behavior 

 throughout in these hybridization phenomena is an elo- 

 quent testimony of the existence of a casual agency of a 

 simpler nature than that called for under the hypothesis 

 of actual, germinal changes. 



Those phenomena included in the third category and 

 dealing with chromosome duplication may be referred to 

 the same type of iregular behavior in gameto^enesis as is 

 concerned in the production of the other ''mutants." 

 They are of interest most particularly from our stand- 

 point with regard to the structural relations which they 

 display in comparison with the other forms. Thus there 

 is a series of lata forms dependent on the duplication of 

 one chromosome in Lamarckiana, They are not identical 

 within the series, but at least three or four are known 

 which differ from one another in a characteristic fashion. 

 This may well be dependent on the particular chro- 

 mosome pair which is concerned in the duplication as 

 Grates (1908) has suggested. According to the chromo- 

 some view of heredity this duplication has the effect of 

 altering the proportions of the various elements in the 

 reaction system, and naturally in a delicately balanced 

 system such alteration results in a change in the somato- 

 genic processes in a definite direction, the latter depend- 

 ent upon which particular elements are increased. Since 

 a whole chromosome with presumably a large set of fac- 

 tors is involved, it should follow that the entire set of 

 characters of the plant would be affected, as appears 

 actually to be the case. The important point in connec- 

 tion with these phenomena is the apparent consequence 

 that phenotypic changes may be dependent merely on an 

 alteration in the relative quantitative proportions of the 



