No. 2.] THE OOGENESIS OF BUFO LENTIGINOSUS. 387 
both cases the nucleus contains a granular reticulum which 
appears to be continuous; and in both oocyte and spermatocyte 
this stage is followed immediately by one in which there is 
a gradual condensation of the nuclear contents leading to 
synizesis (Fig. 25). The beginning of the process of con- 
densation in the odcyte is shown in Fig. 23, where the greater 
part of the chromatin reticulum is seen to be collected in the 
centre of the nucleus. In the following stage the contraction 
of the nuclear reticulum becomes more marked (Fig. 24), 
and eventually all of the nuclear contents forms a more or 
less rounded mass in the centre or at one side of the nucleus 
(Fig. 25). In favorable preparations the contraction figure 
is found to be composed of a tangled mass of exceedingly fine 
filaments in the meshes of which there are several round, 
apparently homogeneous bodies which are doubtless the plas- 
mosomes: a number of the filaments run out from the central 
body and connect this structure to the nuclear membrane. 
At this stage it is impossible to follow in detail the changes 
that are taking place in the nucleus or to determine what 
relation the fine filaments bear to the nuclear reticulum of the 
earlier stage. The condensation of the nuclear contents in 
synizesis is not carried quite as far in the ooyctes of Bufo as it 
is in the spermatocytes where the contraction figure frequently 
appears as a rounded, apparently homogeneous mass con- 
nected by a few fine filaments to the nuclear wall (King, 52; 
Figs. 20-22). 
In toads killed at the time of metamorphosis the ovaries con- 
tain large numbers of secondary oogonia and young oocytes, 
although only a few of the latter have reached the synizesis 
stage at this time. Contraction figures are frequently met with . 
in the ovaries of young toads killed about four weeks after 
their metamorphosis, and they are found very abundantly 
afterwards until the toad has attained a body length of about 
1.5 cm. As I have already pointed out in the case of the 
spermatocytes of Bufo, I do not think it possible that the con- 
traction figures are due to a bad preservation of the material 
as Janssens (47) has asserted is the case in Batracoseps atten- 
