CELL SIZE AND 
TABLE 3 
NUCLEAR 
SIZE 
Le 
Maximum nuclear size and cell size in the blastomeres of Crepidula plana; (measured 
just before nuclear membrane dissolves) 
STAGE 
BLASTOMERES 
| DIAMETER 
OF CELL 
Before maturation. 
Before first cleav- 
APOE Gee eh Oe fae | 
AB, CD, before sec- 
ond cleavage. ...| 
A, B, C, D, before 
third cleavage. ..| 
1A-1D, before 
fourth cleavage... 
la-ld, before divi- 
2A-2D, before fifth 
cleavage.......... 
2a-2d, before divi- 
lal--ld!-, before di- 
WISIOAL soadegecasee | 
3D, before sixth 
cleayage--..... 
3A-3C, before sixth 
cleavage.......... 
3a-3d, before divi- 
4d, before seventh 
cleavage.......... | 
4A-4D, before sev-, 
enth cleavage..... 
4a-4c, before sev- 
enth cleavage...... 
106 
80 
76 
76 
38 
60 
42 
VOLUME 
OF CELL 
cubic 
1,755,000 
1,488,910 
619,329 
286,712 
276,350 
266,240 
228,288 
228,288 
28,533 
112,320 
32,409 
a 
DIAMETER | | VOLUME OF 
f Or | DIAMETER VOLUME (PROTOPLASM,) KERN- 
PROTOPLASM OF OF | LESS PLASMA- 
INCLUDING NUCLEUS NUCLEUS | VOLUME OF | RELATION 
NUCLEUS | NUCLEUS 
be | be cubic uw | cubic pu 
ca. 64* 42 32,409 Q7lstew | W3 
| 930+- 
ca. 65* |*o124=34.5| 21,375 121,430 | 1:5.6 
ca. 51* 24 7,238 61,741 |1:8.5 
i] 
ca. 44* | 22 5,775 | 38,570 1:6.6 
| | 
| | 
ca. 40 DA 4,849 28,481 | 1:58 
30 14 1043 Zen e603 ee ele S27 
ca. 36 | 18 3,055" | 920,196) 4/127 
| 
| 
36 | 15 LTT Wh OesSe we Nie e1D) 7 
| | 
Sema 12 905 13,135 | 1:14.5 
15 | 7 180 PSST lASes 
cao il) Gs 2,145 11,895 |1:5.5 
ca. 22 16 2,145 3,430 |1:1.6 
33 14 1,437 19,250 | 1:13.3 
30 14 1,437 12,608 |1:8.7 
30 14 1,437 12,603 |1:8.7 
ca. 22 ll 697 ARQT Sienna a7 
ca. 20 18 3,055 1,134 | 1:0.37 
ca. 14 12 905 532 | 1:0.58 
* After yolk has been centrifuged out of egg. 
plasm are not well segregated at this stage. 
THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 12, No. 1 
In normal eggs yolk and proto- 
