CELL SIZE AND NUCLEAR SIZE ie 
In eggs in which the nuclear division has been greatly delayed, 
if not entirely stopped, by the use of hypertonic salt solutions the 
nucleoli become much larger than in normal eggs. Thus in the 
eggs of Crepidula plana treated with 4 per cent NaCl solution 
for two hours, and then put into normal sea water for six hours, 
the sizes of nuclei and nucleoli are as follows: 
TABLE 15 
Nucleolar size and nuclear size in eggs of Crepidula plana in hypertonic sea water 
DIAMETER | VOLUME | NuMBER | DIAMETER | VOLUME NUCLEAR- 
STAGE BLASTOMERES OF OF | OF OF OF | NUCLEOLAR 
NUCLEUS | NUCLEUS | NUCLEOLI | NUCLEOLI | NUCLEOLI RATIO 
a cubic | MU cubic 
1 cell, pronuclei...... [\9 24 7,238 | : 12 905 8:1 
Vo 21 4,849 1 10 524 9:1 
DicellseAiBe OD) wascen 24 7,238 1 9 382 OB! 
dicells, Al BY C,D...... 15 1,767 1 9 382 | 4.6:1 
8 cells, 1A-1D.......... 18 | 3,055 1 9 382 Sune 
The great size of the single nucleolus in each of these nuclei 
is probably due to the fact that division has been delayed and the 
resting period prolonged. 
f. Centrosomes and spheres. Finally we may consider in this 
connection the sizes of centrosomes, and spheres though they are 
not parts of the nucleus. In general in Crepidula, large cells 
contain large centrosomes and spheres, while small cells contain 
small ones. The maximum diameters of centrosomes in the 
cleavage of C. plana, vary from 2u to 7yu, the measurements being 
made during the telophase of division. The maximum diameters 
of the sharply defined spheres, during the resting stages, vary 
from 5yu to 12u; and in all cases, so far as I have observed, the 
largest centrosomes and spheres occur in the cells which have 
the largest amount of protoplasm, while the smallest occur in 
the cells with the least amount of protoplasm. 
The centrosomes and spheres are the cell constituents which 
first become unequal in an unequal cell division. As soon as the 
spindle becomes eccentric, the centrosome and sphere which lies 
farthest from the center of the cell becomes smaller than the one 
