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MONTGOMERY. 
[Vol. XV. 
in the nuclear sap, these globules may best be treated first. 
In the nuclear sap, at a certain stage in the growth period of 
the germinal vesicle, small globules of varying size occur ; 
there are usually one or two of them in a given nucleus, but 
sometimes they are quite numerous (Nut. Gl. in Figs. 62, 63, 
69-71, 73, 75, 81). When I first noticed these structures I 
conjectured that they might represent centrosomes such 
as have been found within nuclei at stages previous to mito¬ 
sis (by Brauer in the spermatocytes of Ascaris); but further 
investigation shows that they have no kind of relation to cen¬ 
trosomes, since they vary in number and size, and further they 
readily imbibe stains, which centrosomes do not. They have 
a close resemblance to the smallest yolk granules found in the 
cytoplasm in point of form, size, and manner of staining. How¬ 
ever, sometimes one or two of these bodies may be found in 
the nucleus when there is no evidence of yolk in the cytoplasm. 
Accordingly, they would seem to consist of a substance very 
similar to the young yolk at the time of its first formation. 
And since they may arise in the nucleus before yolk spherules 
appear in the cytoplasm they are probably not always taken up 
by the nucleus from the cytoplasm in the form of globules, but 
acquire this spherical form first in the nucleus. In other words, 
we may consider that the nucleus assimilates from the cyto¬ 
plasm a thin fluid, similar to, if not identical with, that from 
which the yolk spherules themselves are ultimately formed, and 
that in the nucleus this substance becomes deposited in the 
form of globules, perhaps after having undergone a chemical 
change within the nucleus. Further, this substance must be 
regarded as having a nutritive value, on account of its similarity 
to the substance of the yolk, which certainly is nutritive in 
function. In the more mature, larger germinal vesicles (Fig. 
78) large yolk globules are usually found, and are wholly simi¬ 
lar to those in the cytoplasm in these stages ; as can be easily 
determined, their position within the nucleus is not due to 
removal by the knife in sectioning, so that as the nucleus 
becomes larger it regularly takes up large yolk globules from 
the cytoplasm, and from these probably derives the greater 
part of the nourishment necessary for its rapid growth. We 
