22, EDWIN G. CONKLIN 
TABLE 5 
Mean nuclear size and cell size in the blastomeres of Crepidula plana. (Measured 
when nuclei first become spherical after division) 
1 iS n 2} 
fa as! ke A Am 8 4 
STAGE BLASTOMERES © OF ° i me A ees 
es as re ° ofA & 
S Bsa A a asp | 3 
Bo. Bas : B Bae 2% 
a | SE 4 5 BRS ae 
A a a > > 4 
Me be a, cubic pL | cubic 
| f 218 | ‘ 
Before cleavage... .| 136 ca. 60 \ o12 3,960 109,137 ee at 
O ovellilsy INES (CID). «|| OS ca. 44 18 | 3,055 41,240 Inelaee 13.5 
4. ‘cells Aj B,C, Dal. 78 ca. 40 16 | 2a SE 135. uly. 
Peale PASM. 4). ao ca. 36 15 1,767 4 22,484 | 1:12.7 
> itastde..2-) 30 30 | 12 905 » 13,885, >| alae 
oleate 2A-2D....) 72 ca. 36 Sy | AGC | 22, A84A- NGL Fae 
one NDe- Oden <b 136 36 12, | 905) .*|. » 235346" “| Weep 5e6 
iGaneule flai-1d!...| 30 30 9 382 | 13,658, I eson/ 
 \ta2=1d2) 415 15 6 Tes | L654 | 146 
aotcalls 3A-3D....| 72 ca. 18 14 1,437 618 4) eae 
ss BO=aEl 5555) G0) 30 | 12 905 13,135 1:14.5 
Teall 2al2d!...| 27 Path 125) | 905 9,330 | 1:10.3 
Sarde | 27 27 12) 3) 905 9:330))) te i0.3 
209 Mn aie 60 
9 
ag. (cio a 34 | 9 382 
flattids! 15 15 | 6 ee | 1,654 |1:14.6 
29 cells ¢ 
Tal2-1d'2 | 24 24 | 12>) 905 6,333 iL 37 
4A-4C.... il) MevAsyy 
32 , 
ace ae sy | 9 382 
Incidentally the interesting fact appears that nuclei in large 
cells do not become spherical until they have reached a larger 
size than their sister nuclei in small cells; for example in the micro- 
meres Ja-1d and 2a-2d the nuclei become spherical when they 
are about 12 in diameter, in the macromeres 1 A—1D and 2A-2D 
their sister nuclei are about 15y in diameter before they become 
spherical. Since the same amount of chromatin goes into each 
of the sister nuclei, the difference in the size of the nuclei when they 
first become spherical must be found in some other factor. It 
seems probable that it is due to the shape of the chromosomal 
disk, which remains flattened, or slightly arched, in large cells 
