"No, 2.] « THE OOGENESIS OF BUFO LENTIGINOSUS. 409 
which there were many hundreds of nucleoli lying close to the 
nuclear membrane I have never found a single case in which a 
nucleolus was passing through the membrane into the cyto- 
plasm. At certain stages in the development of the ova there 
are a number of rounded bodies in the cytoplasm which greatly 
resemble nucleoli, and it is doubtless this similarity in ap- 
pearance that has led to the assumption that the cytoplasmic 
bodies are of nucleolar origin. 
Soon after the stage of Fig. 49 the nucleoli leave their 
peripheral position and move towards the centre of the nucleus. 
Their arrangement at first is somewhat irregular (Fig. 50) ; 
but later, as shown in a previous paper (King, 49; Fig. 3), 
they form a closed ring which surrounds the chromosomes. 
This arrangement of the nucleoli in the ovarian egg previous 
to maturation seems to be characteristic of all amphibian eggs, 
as it has been noted by all of the observers who have studied 
this period in the development of the ova. All of the nucleoli 
have begun to disintegrate by the time that the germinal 
vesicle breaks down at the beginning of the maturation period. 
They first lose their capacity for staining and many of them 
become vacuolated. Later they break into small fragments 
which are absorbed by the cytoplasm. 
Although this study of the ovarian egg of Bufo has shown 
that investigators of amphibian odgenesis have classed to- 
gether, under the general name of nucleoli, several different 
kinds of structures, it has not, unfortunately, disclosed the 
manner in which these bodies are formed or their function 
in the nucleus. 
From the resting stage of the primary odgonium to the 
synizesis period in the odcyte the nucleus of the germ-cells 
contains several rounded nucleoli which stain differently from 
the chromatin and there is not the slightest evidence that there 
is any genetic relation between them. During synizesis the 
nucleoli can still be distinguished from the chromatin (Fig. 
25); but in early post-synizesis stages (Figs. 26-34) these 
bodies are contained in the amorphous masses of nuclear sub- 
stance (compound-nucleoli) left over after the formation of 
