VITELLINE MEMBRANE AND CORTICAL PARTICLES 271
this objection does not apply to the results obtained by Allen and
Hagström (1955) and by Runnström (1959a,b) in which warming to
32°C for 2 to 3 min was used to interrupt the impulse. The interruption
is typical of a chain reaction. Macromolecules are involved in the propagation process in such an exacting way that slight changes in their conformation are able to block the propagation.
Despite the broad contact remaining between activated and nonactivated region of the egg subjected to heat treatment (Fig. 23B), no
delayed activation occurred in the region that was not encompassed by
the propagating impulse. At the most, the egg underwent a sort of "preactivation" (Kriszat, 1956) which makes it more accessible for activation by hypertonic treatment (Runnström, 1959b). There is no sharp limit
between the activated and the nonactivated region of the egg subjected
to temporary warming. Observations of the transition zone are of great
interest. It is apparent that a series of processes are affected by the
warming, and the time course of the cortical changes are reflected in the
transition zone. In the most distal zone not even the vitelline membrane
is elevated; progressing in proximal direction, an elevated granular
membrane (lamellae are attached to but have not yet merged with the
vitelline membrane), a somewhat folded light membrane, and, most proximally, a smooth membrane are observed. The former appears lighter, the
last one darker in phase contrast. The significance of these different
phases will be discussed in Section III,B-D.
Just (1939, pp. 102, 112) showed for nonpretreated eggs of Echinarachinus parma that the transition zone between activated and nonactivated region is the most susceptible to dilution of the medium. From
here an outflow of cytoplasm may be observed (Just, loc. cit., Fig. 19)
indicating an osmotic disruption in the transition region. The dilution of
the medium may prevent the fusion of the plasma membrane with the
membrane of the cortical particle ; however, it does not prevent the opening of the plasma membrane, and in this way the diluted medium may
enter and cytoplasm escape. This indicates also that the unit membranes
in the egg surface are not united before the passage of the activation impulse. Temporary heating, on the other hand, causes an enhanced gelation that prevents both the opening of the plasma membrane and of the
cortical particle. The gelation depends probably on the action of an
enzyme (E 2, Section II,D). This problem will be briefly considered again
in Section IV,C.
Tyler et al. (1956) and Hiramoto (1959) demonstrated the presence of
a resting electric potential in the surface of the sea urchin egg and a
depolarization of the egg surface upon activation. The latter author
found in the large eggs of the sand dollar Peronella lesueuri a very suit-
this objection does not apply to the results obtained by Allen and
Hagström (1955) and by Runnström (1959a,b) in which warming to
32°C for 2 to 3 min was used to interrupt the impulse. The interruption
is typical of a chain reaction. Macromolecules are involved in the propagation process in such an exacting way that slight changes in their conformation are able to block the propagation.
Despite the broad contact remaining between activated and nonactivated region of the egg subjected to heat treatment (Fig. 23B), no
delayed activation occurred in the region that was not encompassed by
the propagating impulse. At the most, the egg underwent a sort of "preactivation" (Kriszat, 1956) which makes it more accessible for activation by hypertonic treatment (Runnström, 1959b). There is no sharp limit
between the activated and the nonactivated region of the egg subjected
to temporary warming. Observations of the transition zone are of great
interest. It is apparent that a series of processes are affected by the
warming, and the time course of the cortical changes are reflected in the
transition zone. In the most distal zone not even the vitelline membrane
is elevated; progressing in proximal direction, an elevated granular
membrane (lamellae are attached to but have not yet merged with the
vitelline membrane), a somewhat folded light membrane, and, most proximally, a smooth membrane are observed. The former appears lighter, the
last one darker in phase contrast. The significance of these different
phases will be discussed in Section III,B-D.
Just (1939, pp. 102, 112) showed for nonpretreated eggs of Echinarachinus parma that the transition zone between activated and nonactivated region is the most susceptible to dilution of the medium. From
here an outflow of cytoplasm may be observed (Just, loc. cit., Fig. 19)
indicating an osmotic disruption in the transition region. The dilution of
the medium may prevent the fusion of the plasma membrane with the
membrane of the cortical particle ; however, it does not prevent the opening of the plasma membrane, and in this way the diluted medium may
enter and cytoplasm escape. This indicates also that the unit membranes
in the egg surface are not united before the passage of the activation impulse. Temporary heating, on the other hand, causes an enhanced gelation that prevents both the opening of the plasma membrane and of the
cortical particle. The gelation depends probably on the action of an
enzyme (E 2, Section II,D). This problem will be briefly considered again
in Section IV,C.
Tyler et al. (1956) and Hiramoto (1959) demonstrated the presence of
a resting electric potential in the surface of the sea urchin egg and a
depolarization of the egg surface upon activation. The latter author
found in the large eggs of the sand dollar Peronella lesueuri a very suit-