VITELLINE MEMBRANE AND CORTICAL PARTICLES 297
Either it falls back on the hyaline layer or it is broken up and detached.
A very strong unfolding of delayed lamellae was also obtained in Psammechinus eggs when fertilization was brought about in the presence of
5 χ 10"
4
% tannin. Figure 17 of Afzelius (1956) shows strongly unfolded
lamellae comprising filaments curled at their ends. Their length amounted
to about 3 μ.
Treatment with tannin breaks up the cross-linkages within the
lamellae. The extended filaments show a periodic fine structure with
septa at somewhat irregular distances (170-250 Â) from each other. The
space between the septa corresponds to the vacuoles present before the
breakup of the lamellae, the fine structure of which has undergone a
change so that the vacuoles rather resemble parallelograms. The terminal curls were thinner than the main part of the lamellae. The impression gained was that the curl continued one of the walls of the lamellae
and was devoid of the periodic substructure. The ordered structure in
the tannin-treated eggs was reminiscent of the normal lamellae in
Bnssopsis, where a higher order already evolved in the lamellae of the
developing particles. In tannin-treated eggs the continuous fertilization
membrane had the same septal substructure as the nonincorporated
lamellae, although it was not always as distinct. The fertilization membrane as usual contained only one layer of lamellar material.
Fifteen seconds after insemination, eggs were transferred into 2.5 X
10"
5 M porphyrindin, and 80 min later they were fixed for electron microscopy in osmic acid in sea water. In many places, the fertilization membrane was still connected to the boundary of the hyaline layer, and its
full elevation was counteracted in this way. Certain lamellae could be
connected in one direction with the fertilization membrane, in another
with the hyaline layer. These results are of importance particularly because they certify that there are connections between the lamellae and
extralamellar bodies and that an impairment of the membrane elevation
occurs if these connections are not broken up.
Particularly around the site of sperm entrance many delayed lamellae
showed periodic structure. The lamellae were entangled with extralamellar derivatives and villi which were often connected also with the
fertilization membrane in which the periodic structure sometimes was
visible. One delayed lamella was cut transversely in such a way that four
longer and two shorter filaments were seen to radiate from a central
basal region. Within the fertilization membrane different lamellae may
interdigitate so as to produce a structure such as that seen in Fig. 32A.
Its thickness is about 400 Â. An increase in cross-linkage is assumed to
occur within the fertilization membrane so that a framework arises such
as that shown in Fig. 32B. The stickiness of the terminal curls of the
Either it falls back on the hyaline layer or it is broken up and detached.
A very strong unfolding of delayed lamellae was also obtained in Psammechinus eggs when fertilization was brought about in the presence of
5 χ 10"
4
% tannin. Figure 17 of Afzelius (1956) shows strongly unfolded
lamellae comprising filaments curled at their ends. Their length amounted
to about 3 μ.
Treatment with tannin breaks up the cross-linkages within the
lamellae. The extended filaments show a periodic fine structure with
septa at somewhat irregular distances (170-250 Â) from each other. The
space between the septa corresponds to the vacuoles present before the
breakup of the lamellae, the fine structure of which has undergone a
change so that the vacuoles rather resemble parallelograms. The terminal curls were thinner than the main part of the lamellae. The impression gained was that the curl continued one of the walls of the lamellae
and was devoid of the periodic substructure. The ordered structure in
the tannin-treated eggs was reminiscent of the normal lamellae in
Bnssopsis, where a higher order already evolved in the lamellae of the
developing particles. In tannin-treated eggs the continuous fertilization
membrane had the same septal substructure as the nonincorporated
lamellae, although it was not always as distinct. The fertilization membrane as usual contained only one layer of lamellar material.
Fifteen seconds after insemination, eggs were transferred into 2.5 X
10"
5 M porphyrindin, and 80 min later they were fixed for electron microscopy in osmic acid in sea water. In many places, the fertilization membrane was still connected to the boundary of the hyaline layer, and its
full elevation was counteracted in this way. Certain lamellae could be
connected in one direction with the fertilization membrane, in another
with the hyaline layer. These results are of importance particularly because they certify that there are connections between the lamellae and
extralamellar bodies and that an impairment of the membrane elevation
occurs if these connections are not broken up.
Particularly around the site of sperm entrance many delayed lamellae
showed periodic structure. The lamellae were entangled with extralamellar derivatives and villi which were often connected also with the
fertilization membrane in which the periodic structure sometimes was
visible. One delayed lamella was cut transversely in such a way that four
longer and two shorter filaments were seen to radiate from a central
basal region. Within the fertilization membrane different lamellae may
interdigitate so as to produce a structure such as that seen in Fig. 32A.
Its thickness is about 400 Â. An increase in cross-linkage is assumed to
occur within the fertilization membrane so that a framework arises such
as that shown in Fig. 32B. The stickiness of the terminal curls of the