VITELLINE MEMBRANE AND CORTICAL PARTICLES 245
extralamellar body, which in this stage is not yet subdivided, as is also
seen in several other places in the preparation. The lamella and the
extralamellar body seem to be built up of granules about 200 Â wide.
Those contained in the former structure are more electron dense than
those seen in the latter. The lamella and extralamellar body remain
attached to the wall of the germ by connecting fibers. A membrane is
not distinguishable at this stage. Perhaps it arises only after the denser
components of the cortical particles have differentiated. The impression
is also gained that two, or possibly several, germs are in open communication. The stalk of the oocyte is in intimate contact with the follicle cells, as seen in Fig. 15. This suggests that building material is
transferred to the stalk. With further growth of the oocyte, the cortical
particles found in the stalk seem to become scattered in the cytoplasm
where, in the meantime, the formation of the yolk globules has progressed. The cortical particles often keep together in small groups. They
are few in a 3-4 μ thick cortical layer.
The cortical particles are now surrounded by an easily distinguishable
membrane (Fig. 16). Their differentiation is, however, not fully accomplished but progresses also in the more dispersed state of the particles. This may continue until protein synthesis is interrupted upon
maturation of the oocyte. The opinion was expressed in Section Ι,Β,Ι
that even when the cortical particles invade the cortical layer at maturation they are in somewhat varying stages of differentiation.
The membrane of the cortical particles seems to be formed by fusion
of endoplasmic vesicles with ribosomes on their surface. According to the
growth of cortical particles new vesicles may be inserted into the membrane. The close relationship of the cortical particle to a rough endoplasmic vesicle is visible in Figs. 16A and B.
The dense body vesicles (see Section II) also begin as naked bodies. It
could be demonstrated here even better than in the cortical particles that
the membrane originates from ribosome-carrying endoplasmic blisters
which fuse and become one-layered. The details of this process are not
yet clear. The dense body vesicles are often seen to be in close, sometimes open contact with yolk globules. The naked dense body vesicles
may be derivatives of particles (diameter ca. 700 Â) that enter into
the oocyte from the follicular tissue; see Fig. 15 (low oblique arrow).
The protein synthesis supporting the more advanced differentiation of
the cortical particles is most probably brought about by the ribosomes
attached to the membrane in groups that sometimes form an outside
directed protrusion from the membrane. Both lamella and the extralamellar bodies are in direct connections with the membrane. These
connections may mediate a flow of substances or even of granules.
extralamellar body, which in this stage is not yet subdivided, as is also
seen in several other places in the preparation. The lamella and the
extralamellar body seem to be built up of granules about 200 Â wide.
Those contained in the former structure are more electron dense than
those seen in the latter. The lamella and extralamellar body remain
attached to the wall of the germ by connecting fibers. A membrane is
not distinguishable at this stage. Perhaps it arises only after the denser
components of the cortical particles have differentiated. The impression
is also gained that two, or possibly several, germs are in open communication. The stalk of the oocyte is in intimate contact with the follicle cells, as seen in Fig. 15. This suggests that building material is
transferred to the stalk. With further growth of the oocyte, the cortical
particles found in the stalk seem to become scattered in the cytoplasm
where, in the meantime, the formation of the yolk globules has progressed. The cortical particles often keep together in small groups. They
are few in a 3-4 μ thick cortical layer.
The cortical particles are now surrounded by an easily distinguishable
membrane (Fig. 16). Their differentiation is, however, not fully accomplished but progresses also in the more dispersed state of the particles. This may continue until protein synthesis is interrupted upon
maturation of the oocyte. The opinion was expressed in Section Ι,Β,Ι
that even when the cortical particles invade the cortical layer at maturation they are in somewhat varying stages of differentiation.
The membrane of the cortical particles seems to be formed by fusion
of endoplasmic vesicles with ribosomes on their surface. According to the
growth of cortical particles new vesicles may be inserted into the membrane. The close relationship of the cortical particle to a rough endoplasmic vesicle is visible in Figs. 16A and B.
The dense body vesicles (see Section II) also begin as naked bodies. It
could be demonstrated here even better than in the cortical particles that
the membrane originates from ribosome-carrying endoplasmic blisters
which fuse and become one-layered. The details of this process are not
yet clear. The dense body vesicles are often seen to be in close, sometimes open contact with yolk globules. The naked dense body vesicles
may be derivatives of particles (diameter ca. 700 Â) that enter into
the oocyte from the follicular tissue; see Fig. 15 (low oblique arrow).
The protein synthesis supporting the more advanced differentiation of
the cortical particles is most probably brought about by the ribosomes
attached to the membrane in groups that sometimes form an outside
directed protrusion from the membrane. Both lamella and the extralamellar bodies are in direct connections with the membrane. These
connections may mediate a flow of substances or even of granules.