No. 2.] THE OOGENESIS OF BUFO LENTIGINOSUS. 407 
lar to those shown in Fig. 44. A section of the nucleus of an 
egg taken from the ovary of an adult toad killed the latter 
part of April is shown in Fig. 48. The nucleus has nearly 
attained its maximum size, and it is slightly oval, measuring 
0.19 mm. by 0.22 mm. All of the irregularly shaped nucle- 
olar bodies found at the stage of Figs. 44-46 have disappeared 
and the nucleus contains a large number of round or oval 
nucleoli of various sizes which are entirely distinct from the 
chromatin threads. The smallest of the nucleoli, which stain 
like chromatin, have evidently been formed by a fusion of a 
number of the chromatin granules set free by the disintegra- 
tion of the oxychromatin threads. Most of the larger nucle- 
oli stain very intensely at this time and only a few of them 
show, by their lessened capacity for staining, that they have 
begun to dissolve. Since the majority of the nucleoli are 
derived from the resolution of the secondary compound-nucle- 
oli the greater number of these bodies are massed together 
in one part of the nucleus. A few oxychromatin filaments in 
the process of dissolution are still to be found in the nucleus at 
this time. 
During early growth stages the nucleus occupies the centre 
of the ovum, but at or soon after the stage of Fig. 44 it begins 
to move towards the future animal pole of the egg. As at 
this time the nuclear membrane is usually somewhat irregular 
in outline, several investigators have maintained that the 
change in the position of the nucleus is brought about through 
amceboid movement. This explanation does not seem to me 
entirely satisfactory since in some cases the nuclear outline is 
perfectly regular when the nucleus is moving towards the 
upper hemisphere, and when irregularities in the nuclear out- 
line are found they are invariably distributed uniformly around 
the membrane, no matter by what means the egg has been pre- 
served. 
At the time that the nucleus is changing its position the 
greater number of the nucleoli are massed together in one 
part of the nucleus (Figs. 44-48). I have examined many 
eggs in this stage of development and I have always found 
