CELL SIZE AND NUCLEAR SIZE 23 
and is highly arched in small ones, owing to the greater or smaller 
size of the centrosomes, as explained on p. 19. The flattened 
chromosomal plate gives rise to a disk-shaped nucleus, which 
only later becomes spherical, whereas the highly arched plate 
sooner gives rise to a spherical nucleus. 
2. Cell-size and nuclear size in the cleavage of Fulgur carica. 
The eggs of Fulgur carica are the largest gasteropod eggs of which 
I know, while the eggs of Crepidula plana are among the smallest. 
It will be instructive therefore to compare the Kernplasma- 
Relation in these two cases. Table 6 gives the mean nuclear 
size and cell size of the blastomeres of Fulgur. The eggs measured 
‘were fixed, stained and mounted entire, as in the case of Crepi- 
dula plana. Owing to the great size of these eggs it was necessary 
TABLE 6 
Mean nuclear size and cell size in the blastomeres of Fulgur carica 
s§ | 68 | 8 . ce p 
m ee |e B og Of0n8 26 
e ag | ae ep he CLOVES IT Arey 
ga] ge | $8 Eon eee ee hose 
<0 dp | <2 Aa BaP A i pe 
a A | A 5 | = g 
| - | = 
be iy Nf cubic | cubic [ 
Macromeres ; 
AB, CD, before | | | | 
aecond cleavage. . .| 1200 | 200 | 40 33,280 | 4,126,720 | 1 :124 
iN, 1335 (G3. JD), erate ‘third | | 
cleavage. . : 800 | 160 32 | 17,040 | 2,112,880 | 1 : 124 
1A-1D berore fourth cleave | | | | 
EYES eater ee coicen Catto tad, orcas | 800) 160 | 32 17,040) | 21125880) | ll 2 124 
2A-2D, before fifth cleav- | | 
age.. 800 | 160 | 32 17,040 | 2,112,880 | 1 : 124 
3D, heron ae elena: 800 | 160 | 32 17,040 | 2,112,880 | 1 : 124 
3A-8C, before sixth cleav- | | | 
age.. Breese Jett SOO) | 160 AS) | 5G,008) |) 2062412) le Bors 
Atay, before” geieuiln | 
Cleavavewncy tee 2) 768, 160 96 | 460,063 | 1,669,857 [ies 3.6 
Micromeres | | | | | | 
lacidl, Sk Oe ae 80 |, ae. 2,145 | 264,095 | 1 : 127.7 
Fa ee | 80 | 16 2,145 264,095 | 1 : 127.7 
SASSY, oc pit Ret aes ee a | 80 16 2,145 264,095 | 1 : 127.7 
RES Go te A eee SOs Gas 2,145 264,095 | Ped 
| 1 : 124 
Wea Ue ite epic & os & alls 2G A0e a 8h 266 | 33,014 
