20 EDWIN G. CONKLIN 
TABLE 4 
Minimum nuclear size and cell size in the blastomeres of Crepidula plana. (Nu- 
clear plate measured in the late anaphase; cell diameter in early telophase) 
ee et Chk eae eae 
| 8. | Bec zeae ee | 83 : 
hes a 8 |< 5 | ol 2 
a Op Z Am B D 
STAGE BLASTOMERES | © Cie oe fe BAR 5 
| 5 Boe 58 ae | Bae < 
Stipes 28 B ates eevee weet i eS 
Ss tae nea aa | as ae 
a | a | Aa > | > td 
| ob be | Me cubic mh | cubic pL | 
2) cells’ AB, CD..|M105) |) ican 4Gn Oech eLoOR 30,504 | 1 : 160. 
4 cells A,B,C,D,..| ‘78 | ca. 40| 8x3 | 150.6 30,695 | 1: 203.8 
Seibel) oe | ca. 36) 6x3 84.6 | 24,166 | 1 : 285.6 
la-ld ...| 27 | 27 | 6x3 84.6 1023510 |aeat20 
1 delle eee e|? 72 | can 80) Gees ita 13,955 | 1:165 
\a=2dee ee s0ra 30| 6x3 | 8416 J) SB@5R 9) demas 
fe teene le ae 20 30| 5x3 58.8 0 '|) 13,9055) Sees 
\da%Id? .., 15 | 15 | 5x3 5Sas = yell Om Os 1, $29 
Ree sD sy 2, | eee 15| 4x38 37. by) Wyle 720) a alee 
SES wae | al 25| 4x3 37.5 8,087.5 .| 1 : 215.6 
24 cells 2al-2d!...| 24 DAN Ax3 A 3T 8 7200)" 7 195 
oS cella to GON | 5x3 588) | 
Alby thasy wo | 30 | 5x3 58.8 | 
DO NN 24| 4x3 37.5 7,200 | 1:195 
29 cells ¢lat!-Id'! | 15 15 | 4x3 37.5) y= e72Ueon Welk 46 
eee | 24 24| 4x3 Bab h ua Nt), oT 200 Mailer RTOS 
ANEAC, Si, Are Vl B75) anal | 
ce pees ee | | 4x3 37.5 
age, while all the cells of the same generation have nuclear plates 
of about the same size, though their protoplasmic volumes vary 
widely. 
There is a great difference between the maximum and mini- 
mum volumes of the same nucleus, ranging from 1:27 to 1:38, 
while there is a relatively slight difference between the maximum 
and minimum sizes of the plasma and accordingly the Kern- 
plasma-Relation of any blastomeres varies continuously from the 
stage of minimum nuclear volume to that of maximum nuclear 
volume. Hertwig (08) has chosen as the stage showing the 
Kernplasma-Norm, ‘‘das Verhalten der jugendlichen Zelle, welche 
eben aus der Teilung hervorgegangen ist und nun anfangt sich 
