CELL SIZE AND NUCLEAR SIZE 59 
Neither Minot nor Hertwig took account of the fact that a large 
part of the nuclear contents belongs to both nucleus and proto- 
plasm. The ‘Kernplasma-Relation’ depends very largely upon 
the quantity of protoplasmic material temporarily in the nucleus; 
in the 4-cell stage of Crepidula the ratio of nuclear volume to 
protoplasmic volume is 1 : 6.6 when the nuclei are measured at 
their maximum size, but 1 : 203.8 when they are measured at 
their minimum size. Neither of the authors named, in describ- 
ing the enormous growth of the nuclear material during cleavage, 
took account of the growth of the protoplasm during cleavage at 
the expense of the yolk. 
My observations on Crepidula have yielded the following re- 
sults, which bear upon the hypothesis under discussion: (1) 
While the germinal vesicle is absolutely the largest nucleus in the 
early stages of development, it is not so large with reference to the 
protoplasm, and hence according to Hertwig, not in so deep a 
depression, as the nuclei of certain blastomeres, which ex hypo- 
these should be undergoing restoration to normal conditions. 
(2) The growth of nuclear material during cleavage is not nearly 
so great as has been assumed, averaging not more than 10 per cent 
for each division up to the 32-cell stage, and not more than 1 per 
cent for each division after that stage. (3) The growth of proto- 
plasm at the expense of yolk during maturation and early cleav- 
age is considerable, averaging about 6 per cent for each division 
up to the 24-cell stage. (4) The ‘Kernplasma Relation,’ while 
constant for specific blastomeres, is by no means uniform for all 
the blastomeres of a given stage, but may vary from 1 : 1 to 1 : 14 
in different blastomeres of the same generation. (5) The ‘Kern- 
plasma-Relation’ in adult epithelial cells of all three germ layers 
is about the same as in the majority of the blastomeres. (6) The 
absolute size of the nucleus depends upon the quantity of proto- 
plasm in the cell and the length of the resting period (interkinesis). 
(7) The greater part of the nuclear volume consists of material 
which belongs to the protoplasm as much as to the nucleus; 
during the resting period this is taken in osmotically through the 
nuclear membrane, and is given out again at mitosis by the dis- 
solution of that membrane. (8) The immature egg cell, which 
