EFFECTS OX EGGS OF FRESH ^'ATER PULMOXATES 433 
development was normal except for the distribution of the colored 
substances, and on the 11th day a large normal snail hatched 
from the capsule. 
2. Another centrifuged egg was isolated in the 2-cell stage, the 
stratification of the materials being oblique to the cleavage plane, 
so that one cell was chiefly gray and the other chiefly yellow, 
(as in fig. 43). The subsequent cleavage was normal in form and 
on the 2d day an irregular blastula developed, one pole of which 
was clear, the other yellow, while a crescentic area of gray sub- 
stance lay between the two. On the 8th day a normal little snail 
had developed and on the 11th day it hatched from the capsule 
as a large, normal snail. 
3. A centrifuged egg, in which one cell was gray and the other 
chiefly yellow, was isolated in the 2-cell stage. This segregation 
of the colored materials persisted through the early cleavages 
and on the 2d day an irregular parti-colored blastula developed. 
On the 8th day the embryo was dead. 
4. Another egg in which the stratification was oblique to the 
first cleavage plane was isolated in the 2-cell stage, one of the cells 
being gray and the other gray and yellow. In the 4-cell stage 
three cells were predominantly gray and one 3'ellow. On the 8th 
day a normal snail hatched from the capsule. 
Experiment 14- Centrifuged 5 min. after the extrusion of both 
polar bodies and 30 min. before the first cleavage. In the 2-cell 
stage one blastomere was often yellow and the other gray, in the 
4-cell stage two were frequently yellow and two gray. An em- 
bryo abnormal in form and in distribution of the egg substances 
usually resulted. On the 8th day 42 were apparentl\^ normal but 
unhatched, 6 were abnormal and unhatched, and 32 had died 
about the gastrula stage. On the 12th day many of the appar- 
ently normal forms had hatched and were quite normal. 
Expert fuent 15. Eggs of Phj'sa were centrifuged 22 min. after 
the formation of both polar bodies, in the vain attempt to sep- 
arate the gray material as an exovate. The eggs were drawn 
out into long cylinders (fig. 31), the proportions of the three sub- 
stances being about as follows : Gray one-half, clear one-quarter, 
yellow one-quarter. The distribution of these substances in the 
