u 
nutritive pole, and two of the three nearly equal masses into 
which the egg is blocked out lie at the formative end, and 
one at the nutritive end ; the latter is less granular than the 
pear. The three furrows do not tend to meet exactly at the 
centre, but as shown in Figure 6, two minutes later than 
Figure 5, the one which runs down from the polar globule 
inclines to one side so as to meet one of the side furrows before 
the other. During the stages shown in this and the preceding 
and succeeding figures the protoplasm of the whole egg is 
violently disturbed, and the granular matter quivers or dances, 
with what would be called “ Brownian ” motion, were it not 
confined to this particular stage of development. At the 
stage shown in Figure 5, the three lobes a, b and c of the 
trefoil are nearly equal in size, but at the present stage, 
Figure 6, the one at the nutritive end, a , is the largest, and the 
one which is most perfectly separated, c , the smallest. The 
later stages show that this smallest spherule is posterior to the 
larger one, and this figure therefore gives a view of the left 
side of the egg or embryo with its dorsal surface below. For 
the sake of brevity, we may now call the smallest spherule, c ) 
of Figure 6, the first micromere, the next largest, 5, the second 
micromere, and the one at the nutritive pole, a, the macromere. 
In one minute after the stage shown in Figure 6 the verti- 
cal furrow has united with one of the lateral furrows, to sep- 
arate off the first micromere, and the second lateral furrow 
has run in and united with the line thus formed, so that the 
egg is now divided into three separate masses, each of which 
now becomes spherical, as shown in Figure 7. This stage ends 
the first period of activity, and the changes which follow re- 
sult in the gradual obliteration of the sharply defined charac- 
teristics which have been acquired. 
In forty-five seconds after the stage shown in Figure 7 the 
two micromeres, b and <?, have approached and united with 
each other, as shown in Figure 8, and the second micromere, 5, 
has also become fused with the macromere, a , although the 
egg still has its trefoil outline, and is now very similar to the 
stage shown in Figure 5. In another minute Figure 9, the 
fusion of the second micromere, b , with the macromere, a, is 
