16 EDWIN G. CONKLIN 
It is well known that during mitosis the general surface tension 
of a cell increases, and the cell tends to become spherical in shape. 
In measuring the maximum cell size, I have usually taken the 
stage immediately after the nuclear membrane disappears, and 
when the cell approaches a spherical shape. Similarly the mini- 
mum cell size has been determined by measuring the daughter 
cells during the telophase when they are approximately spherical. 
I have confidence in the substantial accuracy of my measurements 
of these maximum and minimum sizes of the purely protoplasmic 
micromeres. The volume of plasma in the yolk-containing 
macromeres is merely an approximation. 
All measurements were made with Zeiss 1/1 micrometer eye- 
piece and 3 mm. homogeneous immersion objective. In all cases 
enough cells and nuclei were measured to give a fair average, 
though there is relatively little variation in the sizes of particular 
cells and cell constituents at corresponding stages in the cell 
cycle. All the eggs studied were fixed, stained and mounted in 
the same manner, so that alterations due to shrinkage should be 
approximately the same in all. 
It is evident from table 3 that while large cells have larger 
nuclei than small cells, the relation of nuclear volume to cell 
volume is not constant. In different blastomeres of the same 
ege the Kernplasma-Relation, measuring nuclei and cells at their 
maximum size, varies from 1:14.5 to 1:0.37; even in purely 
protoplasmic cells it varies from 1 : 14.5 to 1: 8.7. In cells con- 
taining yolk the ratio of nuclear volume to cell volume (includ- 
ing the yolk) varies from 1 : 89.5 to 1 :34.8. In the different 
blastomeres of this egg there is no constant nuclear-plasmic ratio, 
or Kernplasma-Norm. However in different eggs corresponding 
blastomeres have the same Kernplasma-Relation, when measured 
at corresponding stages. The volumes of the protoplasm and of 
the nucleus show little variation in any given blastomere and the 
Kernplasma-Relation of each of the blastomeres named in table 
3 is practically the same in all eggs. Since many of these blasto- 
meres are peculiar in odplasmie constitution and prospective 
significance it is not improbable that the peculiarities in their 
