VITELLINE MEMBRANE AND CORTICAL PARTICLES 233
Clypeaster japonicus which was studied by Endo (1961a) belongs to
another family among the irregular sea urchins. Nevertheless, the type
of lamella resembles particularly that found in Spatangus,
as follows
from a comparison of Fig. 5 of this article with Fig. 3 of Endo. In Clypeaster the lamella is also rather simple. The holes are recognizable, as
are also the granular tongues or spots present within each hole. As in
Spatangus, they form fibrous connections with the wall of the hole.
As described by Lönning (1963) there are a number of "dense bodies"
present in the eggs of Bnssopsis lyrifera (see Fig. 2, horizontal arrow).
They contain a spherical component with a ground structure that resembles somewhat that of the extralamellar bodies. The dense component is
surrounded by a matrix that is limited by a membrane. It is, therefore,
proposed here that they be designated as "dense body vesicles." The whole
dense body vesicle measures ca. 0.45 μ. The spherical dense component
has a diameter of ca. 0.32 μ (the cortical particle has a diameter of ca.
1 μ). The dense body vesicles are certainly not precursors of the cortical
particles. In mature eggs, they are present in reasonably great numbers
beside the cortical particles and are also found after fertilization (cf.
Lönning, 1963, Fig. 4). It seems probable that the dense body vesicles
are mediators of some secretory activity, as some micrographs indicated.
The subcortical bodies (Ci) of Afzelius (1956, Fig. 4) may correspond
to dense body vesicles. In the regular sea urchins so far examined, dense
body vesicles have been found more rarely, and the homology with those
described for irregular sea urchins is uncertain.
A survey will now be given of the structure of the cortical particles in
some of the regular sea urchins. The scheme Fig. 1 refers directly to the
cortical particles in the mature eggs of Paracentrotus
lividus—the
main
material subject to the attention of this writer.
The cortical particles possess a polarity that is more pronounced than
in the Bnssopsis type. A basal, or proximal region can be distinguished
from an apical or distal region. In the proximal region of the particle,
four or five extralamellar bodies are found (Fig. 1, el; Fig. 6A, horizontal arrow). They surround the basal region of the lamella (Fig. 1, br;
Fig. 6A, vertical arrow). As a whole, the lamella has a spongelike structure where the more solid part forms a framework. The interior, less
solid space (Fig. 1, i) is continuous and in open communication with the
external space (Fig. 1, e) from a distal region.
Figure 6B represents a section more distal than the one represented
in Fig. 6A. Two extralamellar bodies are barely visible; instead, the
coiled filaments can be followed. As seen in Fig. 6B, these coils do not
form a continuous helix. An interspace is seen at the vertical arrow; the
horizontal arrow indicates a connection, without intimate fusion, be-
Clypeaster japonicus which was studied by Endo (1961a) belongs to
another family among the irregular sea urchins. Nevertheless, the type
of lamella resembles particularly that found in Spatangus,
as follows
from a comparison of Fig. 5 of this article with Fig. 3 of Endo. In Clypeaster the lamella is also rather simple. The holes are recognizable, as
are also the granular tongues or spots present within each hole. As in
Spatangus, they form fibrous connections with the wall of the hole.
As described by Lönning (1963) there are a number of "dense bodies"
present in the eggs of Bnssopsis lyrifera (see Fig. 2, horizontal arrow).
They contain a spherical component with a ground structure that resembles somewhat that of the extralamellar bodies. The dense component is
surrounded by a matrix that is limited by a membrane. It is, therefore,
proposed here that they be designated as "dense body vesicles." The whole
dense body vesicle measures ca. 0.45 μ. The spherical dense component
has a diameter of ca. 0.32 μ (the cortical particle has a diameter of ca.
1 μ). The dense body vesicles are certainly not precursors of the cortical
particles. In mature eggs, they are present in reasonably great numbers
beside the cortical particles and are also found after fertilization (cf.
Lönning, 1963, Fig. 4). It seems probable that the dense body vesicles
are mediators of some secretory activity, as some micrographs indicated.
The subcortical bodies (Ci) of Afzelius (1956, Fig. 4) may correspond
to dense body vesicles. In the regular sea urchins so far examined, dense
body vesicles have been found more rarely, and the homology with those
described for irregular sea urchins is uncertain.
A survey will now be given of the structure of the cortical particles in
some of the regular sea urchins. The scheme Fig. 1 refers directly to the
cortical particles in the mature eggs of Paracentrotus
lividus—the
main
material subject to the attention of this writer.
The cortical particles possess a polarity that is more pronounced than
in the Bnssopsis type. A basal, or proximal region can be distinguished
from an apical or distal region. In the proximal region of the particle,
four or five extralamellar bodies are found (Fig. 1, el; Fig. 6A, horizontal arrow). They surround the basal region of the lamella (Fig. 1, br;
Fig. 6A, vertical arrow). As a whole, the lamella has a spongelike structure where the more solid part forms a framework. The interior, less
solid space (Fig. 1, i) is continuous and in open communication with the
external space (Fig. 1, e) from a distal region.
Figure 6B represents a section more distal than the one represented
in Fig. 6A. Two extralamellar bodies are barely visible; instead, the
coiled filaments can be followed. As seen in Fig. 6B, these coils do not
form a continuous helix. An interspace is seen at the vertical arrow; the
horizontal arrow indicates a connection, without intimate fusion, be-