VITELLINE MEMBRANE AND CORTICAL PARTICLES 303
upon fertilization. In electron micrographs, fine granules ca. 50 Â wide
were visible outside the compartmented lamellar part of the membrane
in eggs subjected to Ca
2 +
-free sea water. It seems that normally these
granules which are components of the vitelline membrane (Section I,A)
are transformed to continuous sheets or fibers. In certain places the
vitelline membrane was lost, and here lamellae were present, the sliding
of which was incomplete. Thus the fertilization membrane was thicker
in these places. A certain expansion of the lamellae had nevertheless
taken place. An interior sliding may occur which is independent of the
presence of a continuous vitelline membrane. The expansion of the delayed lamellae in the perivitelline membrane testifies to this also. These
lamellae cling, however, to villi or branches of villi. These studies have
thus far been limited to Psammechinus
miliaris.
In the preceding paragraphs it was indicated that the filling substance
could be (acid) mucopolysaccharides from the opened cortical hollows.
Another possibility would be that the retracting villi exude a substance
that enters the fertilization membrane. Anyhow, the retraction of the villi
certainly has an effect on the interior cytoplasm. The accumulation of
cytoplasm rich in endoplasmic vesicles toward the concavity, referred to
earlier, is an example of an interaction between the cortical surface
layers and the inner cortical and endoplasmic cytoplasm. The same
process that occurs in the region of the large concavity takes place, although on a smaller scale, in the more distal regions of the egg in step
with the spreading of the impulse of activation. The experiments with
temporary warming of the eggs to 32°C block the movement by fixing
the transition zone in the gelated state (Sections II,C and ΙΙΙ,Β).
D. Changes in Mechanical and Chemical Properties of the
Fertilization Membrane after Its Elevation
Ever since the early work of Herbst (1893) it has been known that
the fertilization membrane immediately after fertilization is weak and
can easily be removed by shaking the egg. After 4-5 min, however, the
membrane becomes mechanically very resistant (see further Hobson,
1927; Chase, 1935).
Motomura (1950) and Markman (1958) tried to measure the rate of
solidification of the fertilization membrane. The former author used
centrifugation, the latter filtration through gauze under slightly increased
pressure. In Markman's experiments with Paracentrotus
eggs a curve was
obtained (Fig. 33) that shows a minimum stability ca. 3 min after insemination. The maximum stability of the membrane is attained 4-5 min
after insemination. At the time of the first record (1.75 min after insemination) the membrane is already elevated. It may seem peculiar that
upon fertilization. In electron micrographs, fine granules ca. 50 Â wide
were visible outside the compartmented lamellar part of the membrane
in eggs subjected to Ca
2 +
-free sea water. It seems that normally these
granules which are components of the vitelline membrane (Section I,A)
are transformed to continuous sheets or fibers. In certain places the
vitelline membrane was lost, and here lamellae were present, the sliding
of which was incomplete. Thus the fertilization membrane was thicker
in these places. A certain expansion of the lamellae had nevertheless
taken place. An interior sliding may occur which is independent of the
presence of a continuous vitelline membrane. The expansion of the delayed lamellae in the perivitelline membrane testifies to this also. These
lamellae cling, however, to villi or branches of villi. These studies have
thus far been limited to Psammechinus
miliaris.
In the preceding paragraphs it was indicated that the filling substance
could be (acid) mucopolysaccharides from the opened cortical hollows.
Another possibility would be that the retracting villi exude a substance
that enters the fertilization membrane. Anyhow, the retraction of the villi
certainly has an effect on the interior cytoplasm. The accumulation of
cytoplasm rich in endoplasmic vesicles toward the concavity, referred to
earlier, is an example of an interaction between the cortical surface
layers and the inner cortical and endoplasmic cytoplasm. The same
process that occurs in the region of the large concavity takes place, although on a smaller scale, in the more distal regions of the egg in step
with the spreading of the impulse of activation. The experiments with
temporary warming of the eggs to 32°C block the movement by fixing
the transition zone in the gelated state (Sections II,C and ΙΙΙ,Β).
D. Changes in Mechanical and Chemical Properties of the
Fertilization Membrane after Its Elevation
Ever since the early work of Herbst (1893) it has been known that
the fertilization membrane immediately after fertilization is weak and
can easily be removed by shaking the egg. After 4-5 min, however, the
membrane becomes mechanically very resistant (see further Hobson,
1927; Chase, 1935).
Motomura (1950) and Markman (1958) tried to measure the rate of
solidification of the fertilization membrane. The former author used
centrifugation, the latter filtration through gauze under slightly increased
pressure. In Markman's experiments with Paracentrotus
eggs a curve was
obtained (Fig. 33) that shows a minimum stability ca. 3 min after insemination. The maximum stability of the membrane is attained 4-5 min
after insemination. At the time of the first record (1.75 min after insemination) the membrane is already elevated. It may seem peculiar that