This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1900 edition. Excerpt: …of the nucleolus (Fig. 62). Since my observations show that these nucleolar vacuoles are derived from small fluid globules which first appear 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 mitosis (by Brauer in the spermatocytes of Ascaris); but further investigation shows that they have no kind of relation to centrosomes, 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. However, 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 cytoplasm 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…
