46 EDWIN G. CONKLIN 
sap, does not increase in quantity during the cleavage of the egg; 
we have seen that the total volume of all the nuclei of Crepidula 
at the 70-cell stage is about equal to that of the germinal vesicle, 
while in Styela the volume of all the nuclei at the 256-cell stage 
is 77 per cent less than the volume of the germinal vesicle. The 
conclusion is justified, therefore, that the more fluid constituent 
of the nucleus decreases greatly in volume during the early 
cleavage stages, and that the nuclei therefore become denser 
during this period. 
b. Linin. Just as the nuclear sap is proportional in volume to 
the volume of the nucleus as a whole, so also it is evident that the 
linin is more abundant in large nuclei than in small ones. Evi- 
dently it is not possible to determine the volume of linin in a 
resting nucleus, but since the spindle fibers are composed largely 
of linin it is possible by measuring the size of spindles to determine, 
at least in a general way, the relative quantities of linin in different 
nuclei. In the following table the length of the spindle from 
TABLE 13 
Length of spindle in the maturation and cleavage of Crepidula plana 
| | DIAMETER OF PRECEDING 
STAGE LENGTH OF SPINDLE NUCLEUS 
| 
| 
| . nos 
| 
| 
M Me 
Pirstimaturation..t6¢.. 0.0054 42 42 
Second maturation............ 18 == 
Binstyclempare wes saree ace aa 30 34.5 
Second cleavage, AB, CD......| 30 24 
Third cleavage, A, B,C, D.... 27 22 
Fourth cleavage, LA-1D....... 25 21 
Fourth cleavage la-Id.........| 21 12 
Fifth cleavage 2A-2D......... 24 18 
21 15 
Fifth cleavage 2a-2d......... | 
centrosome to centrosome is given for successive cleavages of 
C. plana, the measurements being made in each case in the stage 
of the metaphase. The diameter of the nucleus is also given for 
comparison with the spindle length (table 13). 
In general the diameter of the spindle at its equator is, in the 
prophase and metaphase, about the same as the diameter of the 
nucleus from which it came. Spindles in the protoplasmic ecto- 
meres are relatively larger than the size of the nucleus would lead 
