424 
EDWIN G. CONKLIN 
Say, and of Lymnaea catascopium Say in order to determine 
more fully, than was possible by observation alone, the nature of 
the egg organization and the potency and significance of the dif- 
ferent substances in these eggs. The principal method of experi- 
ment was that of centrifuging the eggs at different stages of 
development and to varying degrees. The freshly laid eggs were 
placed while still in their jelly in small tubes which were whirled 
on a centrifugal machine driven by water pressure. The radius 
of rotation was 6 cm., and the average velocity 3000 revolutions 
per minute, from which data the centrifugal pressure may be cal- 
culated to be approximately 600 times that of gravity. 
Since each egg is contained within a capsule which does not 
collapse under the pressure used, and since these capsules are con- 
tained within jelly masses which keep the capsules well separated 
from one another, all danger of distortion due to mutual pressure 
is avoided. The eggs are free at all times to rotate within the 
capsules; at the same time the capsules are easily isolated, they 
afford a perfectly normal environment for the further develop- 
ment of the eggs, and if substances are separated from the egg 
in the process of centrifuging the further history of these sub- 
stances, as well as the eggs from which they came may be followed 
through the entire course of development until the adult form is 
reached and little snails escape from the capsules. All of these 
features make these eggs unusually favorable for such experi- 
ments. 
Eight separate egg-masses, containing from 25 to 75 eggs each, 
were centrifuged in the germinal vesicle stage. In a few instances 
the eggs were taken just as they were being laid, in other cases 
just before the disappearance of the germinal vesicle, and certain 
slight differences in the results of centrifuging different lots of 
eggs may probably be attributed to this slight difference in the 
stage at which the centrifuging occurred. In all of these cases 
the relative age of the eggs may be determined by observing the 
time at which the first polar body appears, since this usually 
occurs about two hours after the egg is laid. In the following 
account the experiments are described in the order of the age of 
the eggs at the time they were centrifuged, the earliest stages 
