660 THE AMERICAN NATURALIST. (VoL. XXXIX. 
In the evening of the same day, two eggs, a and 4, showed this 
protoplasmic mass extending halfway between the animal pole 
and the opercular ring. On the next day æ had this mass 
extending two thirds of the way to the ring, while 4 was appar- 
ently unchanged. No changes had been noticed in any of the 
other eggs. Thursday showed no particular change in any of 
the eggs. On Saturday morning, the fourth day, a had a trans- 
lucent cap, lighter in color than the rest of the egg, extending 
from the animal pole to one millimeter past the ring (Fig. 5, 4), 
while in ? the protoplasmic mass at the pole came two thirds of 
the way toward the ring, and was grouped in three distinct ter- 
races (Fig. 5, c). The other eggs had merely the protoplasmic 
mass, coming halfway to the ring. 
By three P. m. the same day, the cap of a had grown ı mm. 
measuring 5 mm. from the pole to its edge at its deepest place. 
Before noon the next day it had grown 2 mm. more, measuring 
7 mm. all told. Egg ? had lost its terraces, and gained instead a 
cap, coming to within 3 mm. of the ring, while a third egg, e, 
which had heretofore appeared quiescent, showed a marked ter- 
race. One hour later the cap on é had passed the ring by 3 mm. 
At this time a is represented by Fig. 5, e; by Fig. 5, 4; and c 
by Fig. 5, c. ; 
Monday, the sixth day, at ten a. m., the cap on a was 9 mm. 
deep, and on 4, 5 mm.; c was still in the terrace state, and ter- 
races were showing faintly on d; a also had a tiny white dot, 1 
to 1 mm. below the ring, and in the middle of the flattened part 
of the egg. That same day at five P. m. the cap of a measured 
IO mm. and the white speck was just the same, d’s cap was 6 
mm. deep, the terraces of c and d were unchanged, and terraces 
were beginning to show on e; f and g were as they had been in 
the beginning. By measuring carefully morning and evening 
for several days I found that the average rate of growth of the 
cap after the terrace state was passed, was two millimeters in 
twenty-four hours, and that the time of highest rapidity was 
between ten A. M. and five P. M, as much space often being 
planc then as was covered between five P. m. and ten the next 
morning. 
Tuesday, a and å were progressing at the usual rate of growth, 
