VITELLINE MEMBRANE AND CORTICAL PARTICLES 319
tached to each other, but they are separated in definite steps of the
activation process. One case in point is the separation of the vitelline
membrane from the cytoplasmic surface of the egg and the ensuing break
of the connections between lamellae and the extralamellar bodies. This
precedes in time the breakup of the connections between the flattening
extralamellar bodies and the bottom of the cortical hollows—the remains
of the cortical particles after extrusion of the lamellae. The decisive importance of accurately timed "breakup" processes has been demonstrated
in the preceding survey.
Ordered enzyme activations are instrumental in the "breakup" processes. It was recognized that a joint activation of two (or perhaps several) enzymes may be necessary in certain cases. Enzyme activations
may occur in a cyclic way, one system releasing another system which
may act in a direction opposite to that of the first enzyme system.
The cortical changes occurring upon fertilization or artificial activation
influence the interior structure of the egg and induce, moreover, protein
synthesis and centrosome replication. The first of these latter processes
may occur without necessarily being followed by the second.
Many of the phenomena may seem to be unique for sea urchins. A
comparative survey should, therefore, have been undertaken. This was
not possible within the framework of this article. This is compensated,
however, by the rather recent comparative review by Pasteels (1961).
Acknowledgments
This review is based on lectures given at the international course on embryology,
held in Naples under the circumspect directorship of Professor G. Reverberi in
October, 1963. The author wishes to express his thanks to Professor Reverberi for
the impetus to this survey which supplements the article "Fertilization" in "The
Cell" (Runnström et al, 1959).
I am extremely obliged to Dr. Björn Afzelius, who put at my free disposal his
rich collection of electron micrographs which once served as material for his paper
of 1956. For many years the writer took advantage of the help, collaboration, and
assistance which was offered in Dr. Afzelius' laboratory.
Dr. Jane Baxandall has also permitted me to go over her numerous electron
micrographs pertaining to her immunoelectron microscopic work. I am also very
obliged to her and to Dr. Harold Strecker for their generous help with the manuscript.
Professor Patricia Harris kindly allowed me to include her excellent electron
micrograph referring to the cortical particles in Strongylocentrotus
purpuratus. It
is reproduced above as Fig. 14.
I thank Dr. Tore Hultin, Dr. Gunnar Lundblad, and Dr. Peter Perlmann for
stimulating discussions concerning the problems reviewed here. In the experimental
work the writer enjoyed the companionship of Dr. Β. E. Hagström, Dr. Janis
Immers, Dr. Georg Kriszat, and Dr. Elsa Wicklund. Assiduous help was given by
Mrs. Astri Runnström in the work on living material and by Miss Catharina
tached to each other, but they are separated in definite steps of the
activation process. One case in point is the separation of the vitelline
membrane from the cytoplasmic surface of the egg and the ensuing break
of the connections between lamellae and the extralamellar bodies. This
precedes in time the breakup of the connections between the flattening
extralamellar bodies and the bottom of the cortical hollows—the remains
of the cortical particles after extrusion of the lamellae. The decisive importance of accurately timed "breakup" processes has been demonstrated
in the preceding survey.
Ordered enzyme activations are instrumental in the "breakup" processes. It was recognized that a joint activation of two (or perhaps several) enzymes may be necessary in certain cases. Enzyme activations
may occur in a cyclic way, one system releasing another system which
may act in a direction opposite to that of the first enzyme system.
The cortical changes occurring upon fertilization or artificial activation
influence the interior structure of the egg and induce, moreover, protein
synthesis and centrosome replication. The first of these latter processes
may occur without necessarily being followed by the second.
Many of the phenomena may seem to be unique for sea urchins. A
comparative survey should, therefore, have been undertaken. This was
not possible within the framework of this article. This is compensated,
however, by the rather recent comparative review by Pasteels (1961).
Acknowledgments
This review is based on lectures given at the international course on embryology,
held in Naples under the circumspect directorship of Professor G. Reverberi in
October, 1963. The author wishes to express his thanks to Professor Reverberi for
the impetus to this survey which supplements the article "Fertilization" in "The
Cell" (Runnström et al, 1959).
I am extremely obliged to Dr. Björn Afzelius, who put at my free disposal his
rich collection of electron micrographs which once served as material for his paper
of 1956. For many years the writer took advantage of the help, collaboration, and
assistance which was offered in Dr. Afzelius' laboratory.
Dr. Jane Baxandall has also permitted me to go over her numerous electron
micrographs pertaining to her immunoelectron microscopic work. I am also very
obliged to her and to Dr. Harold Strecker for their generous help with the manuscript.
Professor Patricia Harris kindly allowed me to include her excellent electron
micrograph referring to the cortical particles in Strongylocentrotus
purpuratus. It
is reproduced above as Fig. 14.
I thank Dr. Tore Hultin, Dr. Gunnar Lundblad, and Dr. Peter Perlmann for
stimulating discussions concerning the problems reviewed here. In the experimental
work the writer enjoyed the companionship of Dr. Β. E. Hagström, Dr. Janis
Immers, Dr. Georg Kriszat, and Dr. Elsa Wicklund. Assiduous help was given by
Mrs. Astri Runnström in the work on living material and by Miss Catharina