428 
EDWIN G. CONKLIN 
low or the gra}^ zones and it usually, if not invariably, lay 
out of the axis of stratification. About 40 min. after cen- 
trifuging the germinal vesicle gave rise to a clear spindle-shaped 
figure, the first maturation spindle, which usually lay oblique to 
the axis of stratification, but in some instances was at right angles 
to it. One end of this figure came into contact with the surface 
of the egg, usually near the boundary between the clear and gray 
zones (as in figs. 24,25), and here the first polar body was extruded 
about 1 hr. after the eggs were removed from the centrifuge. 
Just before the extrusion of che polar body the eggs became pear- 
shaped, the gray substance occurring in the narrow end of the 
pear, the clear substance in the constricted region, or neck, and 
the yellow in the larger end. The second polar body was usually 
extruded near to, or immediately under the first. The centri- 
fuged eggs oriented as in the preceding experiments, with the 
gray pole up and the yellow pole down. When floating freely in 
water on a horizontal stage 20 eggs showed the polar bodies on 
the side while 5 did not. When viewed from the side, with the 
stage in a vertical position, the polar bodies were seen to be on the 
clear zone in 10 eggs, on the edge of the gray zone, near the clear, 
in 3 eggs, and on the edge of the yellow zone in 2 eggs, while the 
polar bodies were invisible, probably lying over or under the egg 
so that they could not be seen, in 10 eggs. Therefore, in 25 
eggs all but 5 had the polar bodies on the clear zone, and these 
lay near the clear zone on the gray or yellow. The cleavages of 
these eggs were normal in form though generally abnormal in 
the distribution of the gray and yellow substances. The gas- 
trulae w^re also normal save for the unsymmetrical distribu- 
tion of these substances, and at the end of 12 days all of the 
young snails except one had hatched, and all were normal, or 
nearly so. 
Two eggs of this lot were isolated in the 2-cell stage, one of the 
blastomeres containing all of the gray substance and the other all 
of the yellow. The cleavage, blastula and gastrula stages were 
normal in form, though abnormal in the distribution of these 
substances, and normal snails hatched from the capsules in both 
cases. 
