MONTGOMERY. 
[Vol. XV. 
5*6 
frequent in many egg cells, infrequent in somatic cells of the 
Metazoa , and apparently never present in plant cells. In each 
such egg cell there may be either one nucleolus proper and 
from one to several paranucleoli (this being the most usual case), 
or there may be a single paranucleolus and a few nucleoli 
proper. In the ova of three forms examined by me there were 
two kinds of nucleoli present, namely, in Montagna, Polydora , 
and Rodalia. In my descriptions I have employed the term 
“ pseudonucleolus ” for these secondary nucleoli, since in this 
form they have a different structure from that of the nucleolus 
proper, but nevertheless stain in the same way, so it is difficult 
in this case to decide whether they correspond to paranucleoli, 
and hence I have used the indifferent name “ pseudonucleoli” 
for them. In Polydora we found from one to three paranucleoli 
in the larger germinal vesicles, and these are always apposed to 
the nucleolus. Then the smaller, deeply staining bodies in the 
maturer stages of the ovum of Rodalia may be comparable to 
paranucleoli. Whether the remarkable structures of the germi¬ 
nal vesicles of Tetrastemma catenulatum are paranucleoli, I am 
wholly unable to decide. This problem of different types of 
true nucleoli in the same nucleus is one of the most difficult 
in the study of nucleolar structures, so that it is necessary to 
discuss it more in detail. 
A. Schneider (’ 83 ), Brauer (’9i), and Floderus (’ 96 ) consider 
the paranucleoli to be derivatives of the nucleolus proper, more 
especially to be buds from its surface. Hacker (’93a) considers 
them to be secretions of the chromatin. Flemming (’ 82 ) doubts 
whether “ die Unterscheidung von Haupt- und Nebennucleolen 
eine durchgehende Geltung beanspruchen kann he finds that 
in Anodonta the two are at first in contact, but that later they 
become separated. Giard (’8i) finds in the ovum of a Spionid 
one nucleolus, and later there appears in the nucleus a much 
smaller body, which fuses with the former. Lonnberg (’ 92 ) 
thinks that the paranucleoli may serve for the acquisition of 
nourishment, or may contain reserve nourishment. List (’ 96 ) 
considers that the paranucleoli and the nucleoli of the somatic 
cells are more closely allied to one another than to the nucle¬ 
olus proper of the ova, and that the former two “ mindestens 
