162 WALTER HBEAPE., 
fig. 2 was taken. I tore open these ova and isolated their 
nuclei; the one represented in fig. 3 was flattened by with- 
drawing the fluid in which it was immersed from beneath the 
coverslip, the other two are, as nearly as may be, not under the 
influence of pressure. In all of them a homogeneous nuclear 
substance bounds a central clear space in which lies the 
nucleolus. Besides the nucleolus a small number of large and 
small highly refractile irregular-shaped bodies are contained 
within the nucleus. 
in fig. 4 the nucleolus, which is not bounded by a membrane, 
consists mainly of an aggregated mass of minute granules, a 
single larger granule being embedded in the midst of these. A 
ring of four very large, irregular granules surrounds the nucleolus 
and a few fine granules are contained in the peripheral nuclear 
substance. 
In fig. 5 the boundary of the nucleolus is more distinct, 
and the transparent space surrounding it is well marked. A 
few small and medium-sized granules are contained within the 
nucleolus, while a number of small particles are suspended in 
the nuclear substance. 
Fig. 3 shows still further differentiation. The nucleolus is free 
from granules, is contained within a definite sharply-marked 
outline, and within the nucleolus itself an appearance of radial 
striation may be noticed. A ring of large granules (broken 
by pressure) surrounds the nucleolus and a number of smaller 
particles are distributed peripherally. 
It appears therefore, from an examination of these three 
nuclei, that a single nucleolus only is present, and that a 
variable number of larger or smaller or of both-sized granules 
are also contained within the nucleus. The nucleolus is 
situated in a transparent central portion of the nucleus, while 
in the peripheral homogeneous nuclear substance a number of 
minute highly refractile granules are suspended. A few larger 
irregular-shaped granules may be arranged close around but 
distinct from the nucleolus, while the latter may itself contain 
smaller granules. Whether or not the isolated granules are to 
be regarded as nucleolar material is a question I do not pretend 
