CYTOLOGICAL STUDIES OF CENTRIFUGED EGGS 639 
that if the eggs of Hydatina were put into the filtrate of the origi- 
nal solution that they hatched into normal individuals, which 
in time laid normal eggs. Evidently the sudden change from the 
old solution to the new one, while not affecting the egg within 
the membranes killed the individuals after they had hatched. 
The details of some of the cases are given in the following table. 
TABLE 1 
NO. 
EGGS 
LAID 
CENTRI- 
FUGED 
DIVIDED 
RESULTS 
11-11-20 
11-35 
12-20 
Normal but body bent to one side. 
20 
3.03- 3.08 
3-30 
All but one normal. 
5 
11-25-11-35 
12-10 
12-10-15 
Normal. Four hatched slightly 
abnormal especially at one side. 
3 
11-25-35 
12-10 
12-12 
Hatched but not normally active. 
14 
3-20-30 
'4.00 
4^15 
None hatched. 
8 
3-20-30 
4. 
4-15 
Three hatched. 
9 
11-30-40 
11-20 
In 2-cell when 
Five hatched; normal. 
taken off. 
7 
3-10 
3^ 
3-50 
Four hatched; normal. 
2 
11-10-20 
11-10 
1 going 2-cell; 
Both hatched; normal. 
other not yet. 
3-10 
3-40 
4.06 
Normal. 
Some of the above series were carried out in spring water; 
hence the mortality and abnormality especially in the first and 
fifth record. Failure to hatch can be also ascribed to the same 
factor in several records. The positive cases suffice to show that 
normal embryos may appear without regard to the time of centri- 
fuging, and individual records confirm Whitney's observation 
that these normal embryos belong to all the types of distribution 
of the visible materials of the egg. 
4. CENTRIFUGING THE EGG OF THE FISH 
The distribution of the yolk and protoplasm in the egg of the 
fish is so different from that in other eggs that have been cen- 
trifuged, that its study presents some points of peculiar interest. 
The protoplasm lies at first in a clear zone over the periphery of 
