CELL SIZE AND NUCLEAR SIZE 67 
worthy fact to which attention will be devoted in a future paper, 
viz., that the cell axis, which is marked by the line passing through 
the nucleus and sphere (and centrosome), remains unchanged 
after centrifuging. In the stage shown in fig. 18, the spheres lie 
between the nuclei and the polar bodies in normal eggs, and al- 
though the positions of cytoplasm and yolk, and of the first cleav- 
age plane have been changed in this egg, this cell polarity remains 
unchanged. 
Fig. 16 represents an egg which was centrifuged thirty minutes 
and then left in sea water for twenty hours. Neither this egg nor 
any others of this lot developed far after being centrifuged; it is 
possible that the eggs were injured in some way so that noneof them 
developed, or it is barely possible that the record of the experiment 
is wrong. In all the eggs of this lot the appearance is that of eggs 
which had been under normal conditions for about three or four 
hours after being removed from the centrifuge. 
This egg was evidently centrifuged during the first cleavage, 
which was very unequal, practically all of the cytoplasm having 
gone into the smaller of the two daughter cells. The nucleus and 
sphere in this smaller cell are enormous, whereas in the larger 
yolk cell they are extremely small, indeed no larger than in the 
anaphase stage of division. The chromosomes form a compact 
mass which stains deeply and contains no achromatic material. 
The sphere is small also but the fact that it holds its normal 
position with respect to the nucleus shows not only that the pol- 
arity of the cell remains unchanged, but also that the material 
of the sphere is different from the ordinary cytoplasm. In many 
cases similar to fig. 16 cytoplasm slowly forms around the chromo- 
somes in the yolk cell and ultimately such a cell may develop in 
a normal manner. ‘There is no evidence that cytoplasm ever 
passes through the cell membrane from one cell to another, and 
there is positive evidence that this does not occur. The formation 
of cytoplasm around a mass of chromosomes in a yolk field is 
therefore an occurrence of more than ordinary importance. The 
question has been asked frequently whether the nucleus alone 
can form cytoplasm or the cytoplasm alone a nucleus. It is 
known that the latter never happens; a mass of cytoplasm without 
