The Origin of Ova in the Adult Opossum Page: 12
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12
Formation of Ova
In the adult opossum there seems to be two methods
by which new ova are produced in the ovaries. First, single
cells of the germinial epitheliu enlarge in position and be-
come separated from the epithelial layer of cells; these
move into the tunica albuginea. Here each enlarged cell be-
comes surrounded by smaller neighboring cells and forms a
young follicle (Plates 3 and 4, figures 6, 7, and 8). Second,
an epithelial cell may divide by mitosis which will give rise
to a cell just beneath the germinal epithelia (Plate 5, fig-
ure 9). This cell may likewise form a follicle by becoming
surrounded by smaller neighboring cells; however, this method
is much less common than the former.
The processes involved may be followed in more detail.
Plate 3, figure 6, shows a typical germinal epithelial cell
enlarging in situ. In this and in other cases it can be
shorn that the slightly enlarged cells really represent typ-
ical cells of the surface layer which have increased in size
and assumed a more spherical form; transitions may be found
between the flattened or cubic epithelial cells and the large
spherical cells. After attaining some size, the enlarged
cells move from the epithelial layer and sink into the tunica
albugines where they are encircled by flattened and elongated
cells already present in the tunica albuginea (Plate 4, fig-
ures 7 and 8). Often several cells appear to enlarge at one
region in the germinal epithelium and move in groups into
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Everett, Newton Bennie. The Origin of Ova in the Adult Opossum, thesis, August 1938; Denton, Texas. (https://digital.library.unt.edu/ark:/67531/metadc29912/m1/16/: accessed July 18, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; .