CYTOLOGICAL STUDIES OF CEXTRIFUGED EGGS 597 
from the tap. Keeping the eggs cool gave no better result than 
warm temperatures. 
It was found that a few drops of dilute sperm gave better results 
than when more sperm was added. Mixing the sperm of several 
individuals gave better results, on the whole, than sperm from 
a single individual, although one or more individuals gave as 
good results as the mixed sperm. This means that in mixing the 
sperm the chance of getting good sperm was insured. Individual 
females gave different results even when the other conditions were 
the same; showing that some eggs are better than others. 
The eggs of seven females were centrifuged separately, and 
control sets of each female were kept. All of the centrifuged 
eggs went abnormally, while several of the controls gave normal 
embrj^os. 
The eggs of nine females were separately centrifuged and then 
fertilized. Controls of each were kept. Only a few trochophores 
appeared in the centrifuged lots, while all of the controls were 
normal. Also seven lots of the same eggs were fertilized after they 
had stood 40 and 80 minutes; these went abnormally. Similarly 
five sets centrifuged produced abnormal embryos, whether cen- 
trifuged 75 turns of the handle or only 25 turns. The controls, 
however, were normal. 
Six sets were centrifuged; in each, one part 25 turns, ^ the 
other 50 (or 100) turns. All went abnormally except one set 
which produced swimmers both in the 25 and 50 turned lots. The 
controls were all normal. Evidently certain individuals behave 
differently from others. 
The preceding experiments suggested that something must 
occur in handling the eggs that is injurious to development. I 
put, therefore, whole animals in the water centrifuge and rotated 
them for 20 minutes. At the end of that time it was found that 
the ripe eggs in the animal had been perfectly centrifuged. If 
such animals were put into water the}" laid there their cen- 
trifuged eggs. Sperm was then added in small amount. In two 
^ It takes 3^ minutes for 100 turns; fewer turns in proportionate time. Bauscli 
Sc Lomb's hand centrifuge. 
THE JOURXAI. OF EXPERIMENTAL ZOOLOGY, VOL. 9, NO. 3. 
