304
LIONEL F. JAFFE
vector be ultraviolet light, white light, centrifugation, or a nearby egg,
indentation in suitable hypertonic media is largely restricted to the future rhizoid poles. This effect was observed at 5 hours with centrifuged
eggs and at 8 hours with unilaterally illuminated ones
2
; however, if
another egg is the vector, it does not appear until 10 to 12 hours. The
degree of polarization indicated by such polar shrinkage is not clear;
though there is some suggestion in Reed and Whitaker's data that it is
greater than that needed to establish tentatively the future axis but less
than that needed to do so irreversibly.
In any case, polar plasmolysis plainly indicates that some very early
events in polarization occur in or near the plasma membrane. This is also
shown by an analysis of photopolarization.
As already noted, polarized light induces Fucus eggs to germinate in
the plane of the electric vector (Fig. 4). A closer study of the similar
polarotropic
responses of the spores of the fungus, Botrytis, shows the
tropic photoreceptor molecules of these cells to lie in or just outside of
their plasma membranes (Jaffe and Etzold, 1962). Since it seems safe
to generalize this to the Fucus egg, a peripheral locus for early changes is
indicated again.
Yet another indicator of such a cortical localization is that the only
vector reported not to polarize the egg is unilateral red light (Hurd, 1920;
Mosebach, 1938), the main target of which is obviously central since the
eggs are photosynthetic (Whitaker, 1931a; Jaffe, 1955).
B. Chemical Gradients
1.
Fertilization
The sperms are strongly attracted to the unfertilized eggs by gradients
of some volatile, relatively nonspecific and nonpolar substance. n-Hexane
and some close relatives simulate the action of the attractant but do not
seem to be identical with it (Cook and Elvidge, 1951). Right after fertilization, attraction suddenly ceases, and in Halidrys,
Cystoseira
and
Hormosira, it has been observed that the extra sperms are actually repelled and/or killed (Farmer and Williams, 1898, Knapp, 1931; Osborne,
1948). The first three authors observed a jelly being extruded by the
fertilizing egg which may be the implied sperm repellant and/or spermicide. Perhaps these two sperm-controlling substances also play a role in
the egg polarization process which is the main concern here.
2
Earlier tests were not made.
LIONEL F. JAFFE
vector be ultraviolet light, white light, centrifugation, or a nearby egg,
indentation in suitable hypertonic media is largely restricted to the future rhizoid poles. This effect was observed at 5 hours with centrifuged
eggs and at 8 hours with unilaterally illuminated ones
2
; however, if
another egg is the vector, it does not appear until 10 to 12 hours. The
degree of polarization indicated by such polar shrinkage is not clear;
though there is some suggestion in Reed and Whitaker's data that it is
greater than that needed to establish tentatively the future axis but less
than that needed to do so irreversibly.
In any case, polar plasmolysis plainly indicates that some very early
events in polarization occur in or near the plasma membrane. This is also
shown by an analysis of photopolarization.
As already noted, polarized light induces Fucus eggs to germinate in
the plane of the electric vector (Fig. 4). A closer study of the similar
polarotropic
responses of the spores of the fungus, Botrytis, shows the
tropic photoreceptor molecules of these cells to lie in or just outside of
their plasma membranes (Jaffe and Etzold, 1962). Since it seems safe
to generalize this to the Fucus egg, a peripheral locus for early changes is
indicated again.
Yet another indicator of such a cortical localization is that the only
vector reported not to polarize the egg is unilateral red light (Hurd, 1920;
Mosebach, 1938), the main target of which is obviously central since the
eggs are photosynthetic (Whitaker, 1931a; Jaffe, 1955).
B. Chemical Gradients
1.
Fertilization
The sperms are strongly attracted to the unfertilized eggs by gradients
of some volatile, relatively nonspecific and nonpolar substance. n-Hexane
and some close relatives simulate the action of the attractant but do not
seem to be identical with it (Cook and Elvidge, 1951). Right after fertilization, attraction suddenly ceases, and in Halidrys,
Cystoseira
and
Hormosira, it has been observed that the extra sperms are actually repelled and/or killed (Farmer and Williams, 1898, Knapp, 1931; Osborne,
1948). The first three authors observed a jelly being extruded by the
fertilizing egg which may be the implied sperm repellant and/or spermicide. Perhaps these two sperm-controlling substances also play a role in
the egg polarization process which is the main concern here.
2
Earlier tests were not made.