4io 
MONTGOMERY. 
[Vol. XV. 
mass of irregular granules within the nucleus appears to stand 
in some relation to the growth of the nucleoli, at least there is 
a relatively greater amount of this substance in the larger 
nuclei; it envelops the largest nucleoli and imbibes the same 
stains, though more faintly, with which the nucleoli become 
stained. Now as the gregarine grows, at the same time both 
nucleus and the total mass of nucleolar substance increase in 
size ; but the nucleus cannot grow without the addition of a 
substance or substances to it, which have been derived from 
without. Accordingly, I suppose that the substance of these 
granules has an extranuclear origin, a substance, i.e ., which, hav¬ 
ing penetrated the nucleus from the cytoplasm, undergoes a 
chemical change in the nucleus and there becomes precipitated 
in the form of granules, for no such substance occurs in granu¬ 
lar form in the cytoplasm. The growth of the nucleoli might 
then be explained on the assumption of the intussusception of 
this substance by the nucleoli. This explanation is offered 
merely as a hypothesis, since I cannot prove its correctness 
with the limited material at my disposal. Since no chromatin 
was demonstrable in these nuclei, it remains for future workers 
to show whether the chromatin is in these stages commingled 
with the nucleolar substance, or whether it is represented by 
one of the two substances of which some of the nucleoli are 
composed ; and if so, whether all, or whether only a certain 
number, of the nucleoli are thus partially constituted of 
chromatin. 1 
C. Metazoa. 
a. Egg Cells. 
i. Montagua fiilata (Verr.). 
(Plate 22, Figs. 57-63, 65-87.) 
In the germinal vesicles of this mollusc two kinds of nucleo¬ 
lar structures occur : the true nucleolus, which is of large size 
and almost invariably single ; and certain secondary structures, 
1 For observations of other authors on nucleoli in Gregarinida , cf. the reviews 
of Minchin (’ 93 ), Van Beneden (’ 69 ), Marshall (’ 92 ), Frenzel (’ 93 ), Koelliker 
(’ 49 ), A. Schneider (’ 75 , ’ 83 ), Wolters (’ 91 ), Camoy (’ 84 ). 
