No. 2.] THE OOGENESIS OF BUFO LENTIGINOSUS. 303 
cells of a cyst have claimed. The development of these cells 
is slower than that of the one cell simply because the size of 
the cyst is limited and there is no space for a more rapid 
growth. 
Soon after the stage shown in Fig. 37 the cyst wall is rup- 
tured, owing doubtless to the pressure of the growing oocytes, 
and the larger cell becomes separated from the rest of the cyst 
and surrounded by a membrane which attaches it to the wall 
of the ovary. Inside of this membrane there are always found 
a number of elongated follicle cells which are undoubtedly 
concerned in the formation of the zona pellucida which later 
develops around the egg (Figs. 36, 39). As the other cells 
of the cyst enlarge each in turn becomes similarly attached to 
the ovarian wall. The cysts do not all develop at the same 
rate. In the ovaries of toads with a body length of 1.5 cm. 
one may find some cysts containing odgonia, others filled with 
young odcytes in various stages of development up to that 
shown in Fig. 37, while in many cases the cysts have become 
disorganized and the ova are separately attached to the ovarian 
wall. 
VI. THr NUCLEOLI AND THE LATER GROWTH STAGES OF 
THE OOCYTES. 
The irregular shaped masses of nuclear substance found 
against the nuclear membrane or in the meshes of the chro- 
matin reticulum at the stage of Fig. 26 seem to increase in 
size as the nucleus grows and one of them usually becomes 
much larger than any of the others. These bodies appear 
homogeneous and stain black with iron hematoxylin or 
purple when the preparation is stained with safranin and gen- 
tian violet. When the nucleus has attained a diameter of about 
0.025 mm. and the splitting of the spireme has been com- 
pleted, numerous fine granular fibres are seen to project from 
these masses which do not stain quite as intensely as before 
(Fig. 34). At the next stage (Fig. 35) one obtains the first 
clue to the structure of these bodies. With the use of iron 
