CELL SIZE AND NUCLEAR SIZE 19 
of the chromosomal plate, its degree of curvature and width, is 
dependent in part upon the size of the centrosome. I found in 
1893 that in unequal cell division the centrosomes and asters 
become unequal before the cell division is finished, though in the 
earlier stages of mitosis the centrosomes and asters at the two 
poles of the spindle are equal in size; only after the cell division 
is finished do the daughter nuclei become unequal. The present 
work has confirmed these earlier conclusions and has shown in 
addition that the shape of the chromatic plate at the ends of the 
spindle is influenced by the size of the centrosomes, and hence 
by the equality or inequality of the division. If the centrosome 
is large the chromosomes form a slightly arched plate on its 
surface; if it is small the plate is highly arched. In the former 
case the plate remains relatively wide and the daughter nuclei 
when they are formed are disk-shaped; in the latter the plate and 
the daughter nuclei become more nearly spherical. Therefore, 
in comparing the sizes of chromatic plates it is necessary to meas- 
ure them before this difference in shape appears, i.e., in the late 
anaphase. But even when all these precautions are taken the 
probable error in measuring objects of such small dimensions is 
considerable, but at least these measurements give the relative 
order of magnitude of the chromosomal disks in the different 
blastomeres. 
The minimum cell dimensions occur in the early telophase, when 
the daughter cells first separate; at this stage the cells are nearly 
spherical in form and it is not difficult to calculate their volumes 
with substantial accuracy. While the minimum cell size does 
not occur at precisely the stage when the nuclei are smallest, 
it occurs so soon thereafter that it can make but little difference 
in the detérmination of the Kernplasma-Relation. 
In short the Kernplasma-Relation, when plasma and _ nuclei 
are measured at their minimum sizes, varies in different blasto- 
meres from 1:29 to 1: 285.6. Except in the division of certain 
cells in the fourth and fifth cleavages (2A4—2D and 2a—2d, 2a'-2d! 
and 2a-2d?) there is no appearance of a constant ratio between 
nucleus and plasma in these different blastomeres. In general 
the dimensions of the nuclear plates decrease with every cleav- 
