CYTOLOGICAL STUDIES OF CENTRIFUGED EGGS 599 
removes the membranes. Whether this is the way in which the 
result is reached or not, the facts show why the centrifuged eggs 
failed more often to produce normal embryos than eggs not 
handled. 
The experiment in which the whole animal was centrifuged 
with its included eggs seemed to show that the separation of the 
materials of the eggs was not the cause of abnormal development. 
In order to test this conclusion further a large number of animals 
were tried. In some cases they were allowed to lay a few eggs 
(controls) before placing on the centrifuge, but in most cases the 
females were put on the centrifuge before they had deposited their 
eggs. An equal number of other individuals were allowed to lay 
their eggs undisturbed, and the proportion of normal and abnormal 
lots in the two series compared. The entire animals were cen- 
trifuged for 20 minutes on the water centrifuge. Of the six lots 
all produced normal trochophores. 
When some animals had begun to lay, they were opened and 
pieces of the body containing the eggs put into the tubes of the 
centrifuge and revolved for 50 turns. When examined the eggs 
were found to be well centrifuged. The body was torn open 
and the eggs, set free, were fertilized. In each of the four lots 
many normal embryos were produced. 
It will be observed that these eggs had not come in contact 
with sea water, hence no opportunity for the swelling of the mem- 
brane was afforded, and it seems probable that it may have been 
retained during the process of centrifuging. 
Again four females that had begun to lay were opened and their 
bodies put into the centrifuge tubes and revolved 50 turns. The 
eggs were found to have been well centrifuged. They were ferti- 
lized and each set produced many normal embryos. 
In this and in the last set also those eggs that did not develop 
appeared not to have been fertilized. 
Nineteen females in the shell that had just begun to lay (in 
water containing some sperm) were centrifuged, twelve for 20 to 
25 minutes; seven for only a few minutes. All of the eggs were 
well centrifuged. The animals were opened and the eggs fertilized. 
All the dishes contained normal embryos. 
