The Statnre and Chrom osomes of Oenothera gigas, De Vries. 529 
some cases omitted altogether, the chromosomes of fig. 8 passing 
almost directly into the prophase condition of hg. 10. Fig. 10 shows 
one of the daughter nuclei of the first mitosis in the prophase of 
the second division. The multipolar spindle is being formed by the 
wefts of fibres surrounding the nuclear membrane (which has just 
broken down) being drawn out to a point at certain places on the 
peri})hery of the nucleus. The chromosomes, 14 in number, have 
not changed their position since the disappearance of the nuclear 
membrane. Tliey are clearly bivalents, and a comparison of the 
stages represented in figs. 1 and 8 with fig. 10 shows that no growth 
of the chromosomes has taken place during the period of interkinesis. 
The period from diakinesis to the telopliase of the homotypic mitosis 
is one of distribution of the chromosome elements, without any no- 
ticeable growth in the quantity of chromatin during tliis time. 
2. Cell-size and chromosome number. 
In a preliminary cytological examination of 0. gigas it was soon 
observed that the pollen mother cells were often conspicuously larger 
than in 0. Lamarckiana or any of the other forms examined. A 
series of measurements was then begun, to ascertain whether this 
difference was constant and in how far the size relationships might 
agree with Boveri’s well-known laAV which would lead to the ex- 
pectation that with the double number of chromosomes, the nuclear 
surface and the cell volume in gigas would be double that in La- 
marckiana. 
Comparative measurements were made of the pollen mother cells 
and the cells of various somatic tissues in gigas and Lamarckiana 
in the same stage of development. For instance, the pollen mother 
cells cliosen in gigas were all in the metaphase of the heterotypic 
mitosis, and the other tissues examined were flower tissues from 
sections of young buds in which the pollen mother cells were in the 
same stage. The pollen mother cells of Lamarckiana measured were 
in the telophase of the second mitosis. Apparently no growth of 
the mother cells takes place during the reduction divisions, but any 
growth there may be would tend to diminish the observed size dif- 
ferences between the mother cells of the two forms. These mea- 
surements are to be extended to various regions of the plant. So 
far tliey point with great certainty to the fact that in 0. gigas the 
