54 EDWIN G. CONKLIN 
at the opposite pole. Only after the division wall forms do the 
daughter nuclei become unequal. 
5. Conclusions as to nuclear growth during cleavage. ‘The rate 
and amount of nuclear growth during cleavage is much less than 
is generally believed. Whether the nuclear volume is taken when 
the nuclei are at their maximum, mean, or minimum size, the nuclear 
growth is far from 100 per cent, or a doubling, in each division. In 
Crepidula the nuclear growth is not more than 5 per cent to 9 per 
cent for each division from the 2-cell to the 32-cell stage, and less 
than 1 per cent for each division after the 32-cell stage. At the 
2-cell stage the nuclear volume is least and up to the 32-cell stage 
the chromatin increases at an average rate of about 8 per cent for 
each division. The stage when the volume of protoplasm is 
least, after the egg has reached its full size, is just before the first 
maturation division; between the first maturation and the 24- 
cell stage the protoplasm increases at an average rate of nearly 
6 per cent for each division. At the end of cleavage the ratio of 
nuclear material to protoplasmic differs but little from the ratio 
at the beginning. In Fulgur the nuclear growth from the 2-cell 
stage to the 16-cell stage averages only 2.8 per cent for each divi- 
sion, and the general Kernplasma-Relation remains unchanged. 
In Styela the nuclear growth from the 2-cell to the 32-cell stage 
averages 9.6 per cent for each division; from the 32-cell stage to 
the 256-cell stage it averages only 0.27 per cent for each division. 
Such a rate of growth is not significant and indicates that the 
meaning of cleavage is to be found in something other than the 
increase of nuclear material as compared with the plasma. 
In general the growth of each of the different nuclear constit- 
uents parallels the growth of the nuclear material as a whole, 
though this is not true of the nuclear sap, which belongs to both 
eytoplasm and nucleus. During cleavage the fluid content of the 
egg as a whole decreases, the odplasm becoming more consistent 
in later stages than in earlier ones. The total fluid content of 
the nuclei in the early cleavage stages is much less than that of 
the germinal vesicle; even in the later cleavages the nuclear sap 
is not so abundant, in some animals, as in the germinal vesicle. 
In Crepidula the volume of all the nuclei at the 70-cell stage is 
