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CARL D. LA RUE AND H. H. BARTLETT 
X semialta. Figures 3 and 4 illustrate the typica series and the semi- 
alta series of crosses, respectively. 
Conclusions 
1 . Mass mutation in Oenothera Reynoldsii consists in the production 
of inordinate numbers of mutations, belonging to several characteristic 
types, by certain mass-mutant individuals, which may be looked upon 
as having undergone a premutative modification. 
2. Aside from their mutability, these mass-mutant individuals 
resemble normal f . typica. The production by them of a large number 
of abortive seeds may itself be looked upon as one of the manifestations 
of mutability. 
3. The characteristic mutations form a series, each member of 
which may give rise to the succeeding member. Thus: 
mut. semialta -> mut. debilis, 
mut. debilis mut. bilonga. 
4. Mut. semialta and mut. debilis appear to represent successive 
reduction stages in the mutation series. Mut. bilonga, on the con- 
trary, marks an advance over the other members of the mutation 
series and also over f . typica. 
5. With the exception of crosses involving mut. bilonga, the muta- 
tion crosses are matroclinic. 
6. The cross debilis X bilonga gives a mixture of the two parental 
types. 
7. The facts of inheritance are best explained by the hypothesis 
that two types of non-equivalent gametes, designated as a and j8 
gametes, are normally produced. 
8. The a gametes are usually eggs, and the gametes sperms, but 
mut. bilonga produces both a and j8 sperms. 
9. Mutation in Oenothera Reynoldsii consists in the modification in 
a gametes of factors that have no counterpart in the jS gametes. 
10. Since the sperms of f. typica are /3 gametes, mutations appear 
whenever a mutated a gamete is fertilized. They do not appear as a 
result of segregation. 
