4( )4 Lutx, Triploid Mutants in Oenothera. 



1. The heterotypic mitosis of 21 -chromosome mutants and 

 hybrids may sometimes distribute but 14 chromosomes, - which 

 are destined to remain normal bodies, to the two poles of the 

 spindle. This distribution may be in groups of 7 each, ordinarily, 

 but possibly occasionally in groups of 6 and 8 each. 



2. The reduction division may sometimes distribute all of the 

 21 chromosomes to the two poles of the spindle. This distribution 

 may occur ordinarily, in groups of 10 and 11, but occasionally in 

 groups of 9 and 12. All may remain normal bodies, or a few may 

 afterwards degenerate. 



3. A number of chromosomes anywhere between 14 and 21 

 may sometimes be distributed to the two poles of the spindle at 

 the reduction division. The two groups may be numerically equal 

 in such cases (approximately so when the number is odd), or 

 unequal. All may remain normal bodies, or a few may afterwards 

 degenerate. 



It is assumed for 1,2 and 3 that 14 of the original 21 chromo- 

 somes present at metaphase of the heterotypic mitosis will remain 

 normal bodies. 



4. The failure of one or more chromosomes to be included 

 within a daughter-nucleus at the telophase of the homotypic division 

 may result in the production of a germ cell with a chromo- 

 some number less than that of the number received at the hetero- 

 typic division preceeding. The number may also be reduced, as 

 indicated above, by the degeneration of one or more of the chro- 

 mosomes received by the daughter-nucleus at the telophase of the 

 heterotypic mitosis. Consequently, the somatic chromosome number 

 of an offspring of a 21-chromosome plant does not necessarily 

 represent the sum of the numbers received by the two parental germ 

 cells at the heterotypic division. 



The evidence does not indicate that we shall find one type of 

 reduction exclusively in 21-chromosome mutant A, for example, and 

 another in a sister mutant B. It is possible, in accordance with de Vries' 

 experiments upon the variation of the 'Erbzahleiv in relation to the 

 different positions of the fruits on the plant (5, Bd. II, pp. 414 418), 

 that the type of reduction present in the male and female germ cells 

 of a flower depends upon its position on the plant. We may find, ther- 

 efore, that a single triploid mutant or hybrid may be represented by 

 all types enumerated under 1, 2 and 3, but that each may be restricted 

 chiefly to particular portions of the plant. P'or instance, the reduc- 

 tion division in both the male and female germ cells of the first 

 flowers of a triploid plant might be represented by the Gates 

 type almost exclusively, while that of the late flowers on the same 

 branches (or stem) might exhibit chiefly theGeerts type of reduc- 

 tion, or vice versa. Perhaps also, the first flowers of a weak 



