The Stature and Chromosomes of Oenothera gigas, De Yries. 539 
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stage iii the cold culture this ratio is 1 : 5 and in the warm culture 
1:2. At higher temperature development is more rapid and the 
size of cells, uuclei, and cliromosomes is smaller. The Kernplasma 
relation is therefore constantly changing, as might be expected, ac- 
cording to the stage of development and the conditions of develop- 
ment. The size of the chromosomes depends in part upon the 
length of time betweeu mitoses, which in turn is dependent upon 
the external conditions and the reactiou velocity of the organism; 
and the cell volume is determined approximatelv by the chromatin 
inass, which is in turn conditioned by the plasma muss of the egg 
before cleavage. The cell size is approximately proportional to the 
chromatin mass. 
However, in the case of O. gigas it cannot be doubted that the 
larger sized cells result from the doubling in the number of chro- 
mosomes, and this case closely parallels Boveki’s case of diplo- 
karyotic larvae. The double chromosome number, and not merely 
the mass, is the determining factor, for tliese chromosomes maintain 
their identity in their descendants throughout the life history. Thus 
it is clear that, however the size relations of chromosomes, nuclei 
and cells may change in different tissues and ander different con- 
ditions of development, given a double set of chromosomes at any 
stage, under the sarne conditions, and a new set of Kernplasma 
relations arises at ouce and persists like tlie double number of chro- 
mosomes. 
This appears to the writer to be a cogent argument for the 
genetic continuity of chromosomes from generation to generation. 
The fact that the double number appears suddenly and 
persists is a strong indication of some form of individua- 
lity. According to Fick (1906) the constancy in the number of 
chromosomes is to be accounted for by assuming that this number 
is merely the “best tactical arrangement” for the material of the 
nucleus. But if this is the case, why should the “best tactical ar- 
rangement” suddenly change from 14 to 28? To say that a certain 
number of chromosomes is the best tactical arrangement only gives 
the false appearance of an explanation, for in reality it explains 
nothing. 
Again, why in all hybrids whose parents have different numbers 
of chromosomes, is the number the exact sum of those in the ga- 
metes which united to form the hybrid individual? The cases of 
Drosera longifolia ( x — 20) x D. rotiindifolia ( x — 10) (Rosexberg 
