388 Cooke and Schively on Observations on the 
nucleus and the amount of cytoplasm (Fig. 12). The lower 
cell has a much larger mass of dense cytoplasm. Its 
nucleus is very large, and contains a large dense nucleolus, 
while strands of chromatin pass through its clear cavity. It 
is this cell that later gives rise to the main mass of the 
embryo. The upper cell only forms a small, suspensor-like 
structure of four or five cells. During this two-celled stage 
of the embryo, there is little differentiation between embryo 
cells and albumen cells. But as development progresses, the 
difference constantly increases. The embryo cells become 
relatively much smaller and denser-looking. The albumen 
cells enlarge greatly, stain less and less densely and finally 
develop a great quantity of starch. They also continue to 
increase somewhat in number by division. 
The lower embryo cell then divides in a plane perpen- 
dicular to the first division, giving two nuclei that lie side 
by side (Fig. 13) and later separate by a vertical cell wall. 
Then these two cells each divide in the same horizontal 
plane as the second cleavage, but in a direction on this plane 
at right angles with the direction of the second cleavage. 
The spindle observed here possessed sharply pointed ends 
(Fig. 14). Next these four cells all divide vertically, giving 
an eight-celled stage consisting of two tiers of four cells each. 
Subsequently each of these eight cells divides unequally, 
so that the axis of the spindle must lie in a radius from the 
centre of the mass. After these cells have formed, the 
appearance of a cross-section is as if four oblique radii were 
passing out from the centre of a circle. On the line of each 
radius lie two cells, the inner one smaller, the outer one 
much larger. Later an oblique division wall appears between 
each of these two cells. So these four division walls form 
a diamond, within which lie four small cells, and outside of 
which lie four much larger cells (Plate XXXII, Fig. 16). 
After this sixteen-cell stage further regularity in division 
cannot be traced, though division proceeds rapidly. The 
eight large outer cells frequently divide in a plane perpen- 
