No. 2 .] COMPARATIVE CYTOLOGICAL STUDIES. 425 
The cycle of the formation of the nucleoli may here also be 
divided into three stages, which do not quite correspond to the 
four of Amphipoms gelatinosus . 
First nucleolar stage. — In the smallest germinal vesicles 
found one or two relatively very large nucleoli were present, 
one of them often in the center of the nucleus, the other 
more excentric or even against the nuclear membrane (Figs. 
103, 114, 115). The nucleoli in these smallest nuclei are 
as large or nearly as large as in any of the following stages. 
In germinal vesicles of slightly greater dimensions three or four 
nucleoli may be present, and some of these may have increased 
a little in size ; the amount of nucleolar substance at this stage 
is often so great as to occupy a fifth of the nucleus. They 
now increase in number, until at the close of this period we 
find a considerable number of mostly large nucleoli quite evenly 
distributed through the nucleus (Figs. 104-106, 109, no, 116), 
but often they are at one of its poles more numerous than at 
other points. This stage would seem to correspond to the first 
and second of Amphiporus glutinosus. 
Second nucleolar stage . — The nucleoli continue to increase 
in number but now decrease in size and commence to pass to 
the periphery of the nucleus, until at the end of this period 
they all lie close to the nuclear membrane, are regular in out¬ 
line, and adequal in size (Figs. 107, 119, 122, 124-126, 130, 131). 
At the beginning of this stage numbers of nucleoli may be 
found arranged in chain-like rows, as is to be seen in Fig. hi. 
This would correspond to the third stage of Amphiporus. 
Third nucleolar stage. — Nearly all the nucleoli are close to 
the nuclear membrane, often flattened against it (Figs. 117, 120, 
127, 129, 137, 138). They show signs of degeneration; thus 
they stain less intensely, are irregular in outline, and have a 
vacuolar or granular structure. In the largest germinal vesicles 
their number has apparently decreased and small non-coherent 
masses of granules may be seen, which are probably degen¬ 
erated nucleoli. Sometimes a nucleus may be found in this 
stage in which almost all of the nucleoli contain each one 
large, excentric, lightly stained globule or vacuole (Fig. 117). 
Staining of the nucleoli. — The natural color would appear 
