84 EDWIN G. CONKLIN 
where nuclei and cells are measured at their maximum size it 
varies from 14.5 to 0.37; at mean size from 35.7 to 1.1; at minimum 
nuclear and cell size it varies from 285 to 29. In protoplasmic 
blastomeres, which contain no yolk, the Kernplasma-Relation 
varies from 14.5 to 8.7, when the nuclei are at their maximum size; 
and from 35.7 to 7, when the nuclei are at mean size. In Fulgur, 
at mean size, it varies from 127.7 to 3.6 (pp. 16-24). 
4. In different eggs, corresponding blastomeres have approxi- 
mately the same Kernplasma-Relation; but in different blasto- 
meres of the same egg or of different eggs the Kernplasma-Relation 
is neither a constant nor a self regulating ratio. It appears to 
be a result rather than a cause of the rate of cell division, and con- 
sequently a variable rather than a constant factor (pp. 24-25). 
5. In the tissue cells of adult Crepidulas there is no marked 
increase of cytoplasm over nucleus, as compared with the blasto- 
meres. The Kernplasma-Relation of various adult epithelial 
cells, not filled with metabolic products, varies from 28 to 7; in 
odcytes and ganglion cells it varies from 6 to 3 (pp. 25-28). 
6. The size of the nucleus is dependent upon at least three 
factors: (a) The initial quantity of chromatin (Boveri); (b) 
The volume of the cytoplasm; (ce) The length of the resting period 
(Dp. 2 
7. The inciting cause of cell division in Crepidula is not found 
solely in the limitations of the working sphere of the nucleus 
(Strasburger), nor in the doubling of the volume of the chromo- 
somes (Boveri), nor in a Kernplasma-Spannung (Hertwig), but 
rather in the coincidence of centrosomal, chromosomal and cyto- 
plasmic rhythms, which are probably connected with the rate and 
nature of metabolism in the cell (pp. 29-32). 
8. During the cleavage of the egg of Crepidula plana the volume 
of the cytoplasm more than doubles between the 1-cell and the 
24-cell stage the average growth for each division being about 
6 per cent; the yolk decreases in volume by nearly one-half and 
the entire egg is smaller at the 24-cell stage than at the 1-cell 
stage. This can only mean that the yolk contributes to the 
growth of cytoplasm during the cleavage period (pp. 32-36). 
