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MONTGOMERY. 
[Vol. XV. 
contains a single large, unstaining globule, which appears as 
a vacuole (Figs. 162, 17 5-177) ; or there may be from one 
to three minute globules in it, which, when seen in their 
entirety, present the optical appearance (due perhaps to refrac¬ 
tion) of black granules, which might be mistaken for solid 
bodies. The nucleolus has no limiting membrane. The largest 
are relatively enormous and stain more intensely with eosin 
than the smaller ones. There is no clear zone in the nucleus 
around the nucleolus. 
In Linens the study of the metamorphoses of the nucleolus 
is complicated by the occurrence of nuclei in various mitotic 
stages. Karyokinetic figures were absent in the ovarial stages 
of the other nemerteans examined, so that in those species 
the connective-tissue nuclei and the egg nuclei both stand in 
the same cell generation, and the germinal vesicle may either 
be regarded as equivalent to an ovogonium or to a true ovocyte 
of the first order. In those species no cell generation separates 
the connective-tissue nucleus and the germinal vesicle, but the 
latter is merely evolved from the former by a gradual process of 
differentiation. But in Lineus the germinal vesicle is separated 
from the connective-tissue nucleus by at least one and prob¬ 
ably by two or three generations (if the differences in the size 
of the cells offer a sure criterion). Here, accordingly, the 
indifferent connective-tissue cell represents an ovogonium, and 
perhaps another generation of ovogonia may intervene before 
the germinal vesicle, the ovocyte of the first order, is produced. 
Of the two individuals on which these nuclear studies were 
made, I found mitotic stages in only one individual, while 
none were to be seen in the other individual, though here 
these nuclei had reached nearly the same degree of devel¬ 
opment. I have studied the mitosis merely with regard to the 
behavior of the nucleolus. The most abundant stages were 
those of the spirem and dispirem, asters and dyasters being 
much less frequent (Figs. 163, 166, 169, 170-172) ; the time 
duration of the latter stages may be less than that of the 
former. In by far the greater number of the spirem stages one 
nucleolus was present; it is probably present in each nucleus 
of this stage, but sometimes may escape observation by being 
1 
