VITELLINE MEMBRANE AND CORTICAL PARTICLES 307
to the conclusion that a substance secreted from the egg is instrumental
in the transformation of the delayed lamellae and the fertilization membrane. The secretion may contain a basic precipitating substance along
with an oxidizing one, the two are possibly combined within one and the
same molecule.
In view of the highly organized structure of the lamellae the possibility
that enzymes are present within the elevated fertilization membrane
cannot be excluded. It may not suffice that an oxidizing substance is
brought to the membrane ; an enzyme may also be needed to enhance the
oxidation process. Moreover, it is possible that the fertilization membrane contains the gelating enzymes (E 2). The role of Ca
2+ may also
be to activate this enzyme. The effect of MTF is not a specific one.
It brings also about a gelation in the perivitelline space that damps
the Brownian movements of the transformed lamellae. As was pointed out
earlier in this section, there are also strong reasons to believe that MTF
is the factor released from the egg which precipitates the substance of
the jelly coat—the "jelly precipitating factor" according to E. Hultin
et al. (1952) or "antifertilizin" in the terminology of Fr. Lillie (1919).
It is also of considerable interest that a change in the cortical layer
occurs simultaneously w
T
ith the solidification of the fertilization membrane. The evidence is that the type of plasmolysis of the fertilized
eggs in hypertonic sea water changes from the smooth to the angular
type (for references see Runnström, 1928b, 1949). The angular type
may be the consequence of a gelation of the cytoplasmic cortex and of
the hyaline layer. There is thus the possibility that a rather general
trend in the direction of a gelation of the surface layers occurs some
5 min after fertilization. This gelation may be of importance also for a
solidification of the boundary of the hyaline layer.
Motomura (1957) considers that MTF, before fertilization, is present
in large vacuoles that form a regular layer below the cortical particles
of the eggs of Hemicentrotus
pulcherrimus.
The present writer never
found in his material any vacuoles of the size and regular arrangement
of those delineated by Motomura. In the fertilized eggs, however, a
number of vacuoles of variable size, often with a diameter of about
500 Â, were found. This measurement includes the comparatively thick
wall which has a width of about 125 Â. These are suspected of being
secretory vacuoles that may contain MTF. Ribonuclease added to an
egg homogenate enhances the release of MTF (Runnström et al. } 1955).
When considering the previous discussion, the question about the
propagated activation impulse takes on a more complicated aspect
than before. At least, primary, secondary, and tertiary waves must be
distinguished.
to the conclusion that a substance secreted from the egg is instrumental
in the transformation of the delayed lamellae and the fertilization membrane. The secretion may contain a basic precipitating substance along
with an oxidizing one, the two are possibly combined within one and the
same molecule.
In view of the highly organized structure of the lamellae the possibility
that enzymes are present within the elevated fertilization membrane
cannot be excluded. It may not suffice that an oxidizing substance is
brought to the membrane ; an enzyme may also be needed to enhance the
oxidation process. Moreover, it is possible that the fertilization membrane contains the gelating enzymes (E 2). The role of Ca
2+ may also
be to activate this enzyme. The effect of MTF is not a specific one.
It brings also about a gelation in the perivitelline space that damps
the Brownian movements of the transformed lamellae. As was pointed out
earlier in this section, there are also strong reasons to believe that MTF
is the factor released from the egg which precipitates the substance of
the jelly coat—the "jelly precipitating factor" according to E. Hultin
et al. (1952) or "antifertilizin" in the terminology of Fr. Lillie (1919).
It is also of considerable interest that a change in the cortical layer
occurs simultaneously w
T
ith the solidification of the fertilization membrane. The evidence is that the type of plasmolysis of the fertilized
eggs in hypertonic sea water changes from the smooth to the angular
type (for references see Runnström, 1928b, 1949). The angular type
may be the consequence of a gelation of the cytoplasmic cortex and of
the hyaline layer. There is thus the possibility that a rather general
trend in the direction of a gelation of the surface layers occurs some
5 min after fertilization. This gelation may be of importance also for a
solidification of the boundary of the hyaline layer.
Motomura (1957) considers that MTF, before fertilization, is present
in large vacuoles that form a regular layer below the cortical particles
of the eggs of Hemicentrotus
pulcherrimus.
The present writer never
found in his material any vacuoles of the size and regular arrangement
of those delineated by Motomura. In the fertilized eggs, however, a
number of vacuoles of variable size, often with a diameter of about
500 Â, were found. This measurement includes the comparatively thick
wall which has a width of about 125 Â. These are suspected of being
secretory vacuoles that may contain MTF. Ribonuclease added to an
egg homogenate enhances the release of MTF (Runnström et al. } 1955).
When considering the previous discussion, the question about the
propagated activation impulse takes on a more complicated aspect
than before. At least, primary, secondary, and tertiary waves must be
distinguished.